Paracetamol Synthesis & Crystallization with Acetic Anhydride in Various Solvents, Exams of Statistics

Download Paracetamol Synthesis & Crystallization with Acetic Anhydride in Various Solvents and more Exams Statistics in PDF only on Docsity! rey NAWI Graz muleTU Natural Sciences Graze AFFIDAVIT I declare that I have authored this thesis independently, that I have not used other than the declared sources/resources, and that I have explicitly indicated all ma- terial which has been quoted either literally or by content from the sources used. The text document uploaded to TUGRAZonline is identical to the present master‘s thesis. Date Signature fünf Hauptversuchen erwies sich das Setup als erfolgreich, mit einer Kristallisationsausbeute von 21,24%. Die Überführung der Suspension mit dem hohem Feststoffgehalt vom Tank zum Synthesereaktor und in weiterer Folge zw. Kristallisator und Filtereinheit ist jedoch immer noch ein Problem, obwohl das Verfahren erfolgreich war. Acknowledgement Behind every success, there is a huge support system which makes it withstand. My support system was overseas and everywhere in this big universe. I would like to start by thanking my advisor Ass.Prof. Heidrun Gruber-Wölfler; Heidi, you weren’t just a mentor to me, you are a role model for women in science. A devoted worker, mother, and a team leader. Thank you for this opportunity and your patience over the last period of time. I wish you a future full of innovation. I would like to also thank my coSy & Pro team, especially Christoph and Manuel for all their support and help, the visiting scientist during this thesis Vaclav Svoboda from CMAC® Glasgow, Scotland. Now let me please to start thanking the people who were there for me overseas. Of course, I would like to thank every single person in my family and friends but on the top of the list is my mother for always believing in me and handling my absence from home. My dad, for his continuous help and support as a chemical engineer, as well as his financial support to me to achieve my dreams here in Austria. To my sister, Razan, and Brothers Ahmed & Mohammad, you have always looked at me as a genius brain moving around and making sure to mention that to every person you meet. Thanks for being there for me. For my friends who are now spread in every corner in this world. Fatima, I wished that you were with me in Austria as you were with me in Germany but you made sure to cover the absence. Alia, despite the huge time difference between Pullman, US, and Graz, Austria we have made it shorter with our phone calls! To my little family in Graz, thanks a lot for all of you. Carolina, thanking you wouldn’t be enough, you were with me in this journey and that definitely makes you my sister from another mother. Snezana, our friendship is the best example for the integration of two different worlds. Also, I would like to thank the Afro-Asiatische institute for accepting me in their team for the last two semesters. Being part of your team helped me meet many great people, like Salem and Karolina, who supported me a lot in the last two semesters. Dear reader, I am sorry for the long thanking page. But for me, coming out from my comfort zone wasn’t easy at all and I quote from Stephen Hawking: “Remember to look up at the stars and not down at your feet. Try to make sense of what you see and wonder about what makes the universe exist. Be curious. And however difficult life may seem, there is always something you can do and succeed at. It matters that you don't just give up.” Table of Contents I. Introduction .................................................................................................................. 1 II. Theoretical Background ............................................................................................... 3 III. Materials and Methods .............................................................................................. 15 IV. Results and Discussion ............................................................................................... 19 4.1 Solubility data ....................................................................................................... 19 4.2 HPLC-Analysis (calibration curve) ...................................................................... 22 4.3 Challenges with 4-aminophenol ........................................................................... 28 4.4 Investigation of impurities behavior ..................................................................... 30 4.5 Paracetamol synthesis without impurities ............................................................ 44 4.6 Paracetamol synthesis with impurities ................................................................. 49 4.7 Synthesis and crystallization of paracetamol ....................................................... 60 4.8 Crystal purity ........................................................................................................ 69 4.9 Influence of different solvent on particle size and shape ..................................... 75 4.10 Continuous set-up ........................................................................................... 77 V. Conclusion and Outlook ............................................................................................ 97 VI. References ................................................................................................................. 99 List of tables 2.1 Paracetamol solubility in different solvents at 25° C, reference [17] 5 2.2 Known impurities in paracetamol and compounds used in this work 10 2.3 Comparison between the effects of the impurities, reference [2] 11 3.1 All materials that have been used with the supplier name, CAS number and purity percentage. 15 3.2 Pipe types, sizes and manufacturer for the continuous set-up 16 3.3 Devices that have been used with the manufacturer’s name and device number 16 4.1 Theoretical & experimental properties for the tested material in HPLC with methanol 5%: HPLC-water 95% mobile phase 22 4.2 Calibration factors obtained from the mobile phase methanol 5%: HPLC-water 95% 24 4.3 Theoretical & experimental properties for the tested material in HPLC with methanol: buffer mobile phase 25 4.4 Calibration factors obtained from the mobile phase methanol 5%: buffer 95% 27 4.5 Batch trials for re-crystallization 4-aminophenol 28 4.6 Acetanilide reaction information with acetic anhydride in water 31 4.7 Reaction sampling at different time intervals for acetanilide with acetic anhydride in water reaction 32 4.8 Acetanilide reaction information with acetic anhydride in iso-amyl alcohol 34 4.9 Reaction sampling at different time intervals for acetanilide with acetic anhydride in iso-amyl alcohol reaction 34 4.10 Metacetamol reaction information with acetic anhydride in water 36 4.11 Reaction sampling at different time intervals for metacetamol with acetic anhydride in water 37 4.12 Metacetamol reaction information with acetic anhydride in iso-amyl alcohol 38 4.13 Reaction sampling at different time intervals for metacetamol with acetic anhydride in iso-amyl alcohol reaction 39 4.14 4-Nitrophenol reaction information with acetic anhydride in water 40 4.15 Reaction sampling at different time intervals for 4-nitrophenol with acetic anhydride in water reaction 41 4.16 4-Nitrophenol reaction information with acetic anhydride in iso-amyl alcohol 42 4.17 Reaction sampling at different time intervals for 4-nitrophenol with acetic anhydride in iso- amyl alcohol 42 4.18 Paracetamol synthesis reaction information in iso-amyl alcohol with acetic anhydride 45 4.19 Reaction sampling at different time intervals for the synthesis of paracetamol in iso-amyl alcohol 45 4.20 Paracetamol synthesis reaction information in 2-propanol with acetic anhydride 46 4.22 Paracetamol synthesis reaction information in water with acetic anhydride 47 4.23 Reaction sampling at different time intervals for paracetamol with acetic anhydride in water 47 4.24 Paracetamol synthesis reaction information with impurities in iso-amyl alcohol with acetic anhydride 49 4.25 Reaction sampling at different time intervals for synthesis of paracetamol and impurities in iso- amyl alcohol 50 4.26 Paracetamol synthesis reaction information with impurities in water with acetic anhydride 52 4.27 Reaction sampling at different time intervals for paracetamol and impurities with acetic anhydride in water 53 4.28 Paracetamol synthesis reaction information using re-crystallized 4-aminophenol 54 4.29 Sampling at different time intervals for the synthesis of paracetamol with acetic anhydride in water using re-crystallized 4-aminophenol 55 4.30 Paracetamol synthesis reaction information with impurities in 2-propanol with acetic anhydride 58 4.31 Results of samples taken at different time intervals for the synthesis of paracetamol and impurities with acetic anhydride in 2-propanol 59 4.32 Synthesis yield comparison among different solvents 59 4.33 Paracetamol synthesis and crystallization in water 61 4.34 Sampling at different time intervals for paracetamol crystallization in water 62 4.35 Paracetamol synthesis and crystallization in 2-propanol 63 4.37 Paracetamol synthesis and crystallization in iso-amyl alcohol 66 4.38 Sampling at different time intervals for paracetamol crystallization in iso-amyl alcohol 67 4.39 Synthesis and crystallization yield comparison among different solvents 68 4.41 Crystal purity test information for the paracetamol synthesis with impurities & acetic anhydride in water 70 4.42 Crystal purity test information for the paracetamol synthesis with acetic anhydride in 2- propanol 70 4.43 Crystal purity test information for the paracetamol synthesis without impurities with acetic anhydride in water 71 4.44 Crystal purity test information for the paracetamol synthesis without impurities with acetic anhydride in 2-propanol 71 4.45 Crystal purity test information for the paracetamol synthesis without impurities with acetic anhydride in iso-amyl alcohol 72 4.46 Crystal purity test information for the paracetamol synthesis with impurities & acetic anhydride in water with impurities 72 4.47 Crystal purity test information for the paracetamol synthesis with impurities & acetic anhydride in 2-propanol 73 4.48 Crystal purity test information for the paracetamol synthesis with impurities & acetic anhydride in iso-amyl alcohol 73 4.49 Comparison between synthesis and crystallization yield among different synthetic reactions and solvents 74 4.50 Materials and amounts that are used in the continuous set-up for 1 residence time 78 4.51 Materials and amounts that are used in the continuous set-up for 2.5 residence time 78 4.52 Paracetamol synthesis reaction information using the continuous set-up 79 4.53 Used flow rates in the set-up 79 4.54 Sampling at different time intervals for the synthesis of paracetamol using continuous set-up 83 4.55 Sampling at different time intervals for the crystallization of paracetamol using continuous set- up 84 4.56 Trial (4) sampling at different time intervals for the synthesis of paracetamol 88 4.57 Trial (4) Sampling at different time intervals for the crystallization of paracetamol 89 4.58 Trial (5) Sampling at different time intervals for the synthesis of paracetamol 93 4.59 Trial (5) Sampling at different time intervals for the crystallization of paracetamol 94 1 I. Introduction 1.1 Background This thesis is a continuation of the work of Ass. Prof. Heidrun Gruber-Woelfler during her stay at CMAC (Centre for Innovative Manufacturing in Continuous Manufacturing and Crystallisation) Glasgow, Scotland. The project’s main goal was the development of a continuous process for the integrated synthesis and crystallization of paracetamol using different solvents, which are: iso-amyl alcohol, 2-propanol and water. Paracetamol was successfully synthesized out of 4-aminophenol and acetic anhydride in batch and continuous flow within 1 minute with 100% conversion using all mentioned solvents. Crystallization of paracetamol was only done out of water in batch and in continuous flow. The continuous process was successfully coupled, but with only 15% overall yield. Thus, in continuation to that work, this thesis was designed [9]. 1.2 Paracetamol Paracetamol (acetaminophen or N-(4-hydroxyphenyl) acetamide) is an analgesic and antipyretic painkiller which is used for the treatment of fever. There are more than 20 products available in the pharmacies with some of them being used for the treatment of influenza in different types of formulations. It is considered a safe drug but with dangerous side effects when used in large amounts [8]. 1.3 Main goal and objectives The main goal of this thesis is the set-up of an integrated synthesis and crystallization process for the continuous manufacturing of paracetamol. The synthesis of paracetamol with different types of solvents with the addition of certain types and quantities of industrial impurities were investigated to determine their effect on the crystal growth. The science behind synthesis and crystallization of paracetamol is known and it has been studied for a long time. To the best of my knowledge it has never been coupled in one process. 2 The schematic diagram in scheme (1.1) shows the involved steps of the production of paracetamol in the usual batch process. The red block indicates the integration of the synthesis and crystallization processes. For simplicity, only the last step of the paracetamol synthesis was taken into account as shown in scheme (1.2). The main reaction of 4-aminophenol with acetic anhydride gives paracetamol with acetic acid as a side product. This reaction is carried out in three different solvents; iso- amyl alcohol, 2-propanol and water. Furthermore, the reaction is carried out with and without the addition of impurities. Scheme 1.1 Involved steps from the manufacturing steps for paracetamol Scheme 1.2 Reaction equation for the last step of paracetamol synthesis 3 II. Theoretical Background In order to build a continuous set-up, a comprehensive understanding is needed and has been studied with the science behind paracetamol as an active pharmaceutical ingredient (API), its solubility, its synthesis from p-aminophenol & the accompanying impurities for the process, as well as the crystallization and continuous manufacturing. This chapter will cover these topics to understand the experimental design in the next chapters. First, an explanation is given about paracetamol as an API from different aspects which is: history, therapeutic significant, clinical treatment and worldwide popular products. 2.1 History of Paracetamol Paracetamol was discovered by mistake! In the 1880’s Professor Kussmaul from the Department of Internal Medicine University, treated intestinal worms with naphthalene. However, his assistants gave the patients acetanilide instead of naphthalene and that resulted in reducing fever temperature. The assistant immediately registered her invention. Shortly after it was a product on the market for a cheap price but it had many side effects. From then on, developments have been done which led to a new compound that's less toxic than acetanilide. The new compound was named as “Phenacetin". However, long-term usage showed negative effects on the kidney. The synthesis trials were kept until 1893 when Joseph von Mering invented paracetamol. Nevertheless, he thought it would cause the same side effects as acetanilide. This misleading idea stayed until the 1940's. A small amount of paracetamol was found present in patients dosed with phenacetin. In 1953, Starling-Winthrop Co. marketed paracetamol and it was more preferable than Aspirin®. It was also believed that the antipyretic and analgesic effects of phenacetin are caused by the presence of paracetamol [1, 8]. 6 2.7 Synthesis of Paracetamol The synthesis of paracetamol on the industrial level is accomplished in four main routes all over the world. The four routes are: 1: Phenol route, 2: p-Nitrochlorophenol route, 3: Nitrobenzene route, 4: Hoechst-Celanese process (p-Hydroxyacetophene hydrazine route). Route numbers (1, 2 (3) have been used for a longer period of time compared to route (4) which gained interest and was used in 1990. A schematic diagram explaining each reaction route is given in the following: [16, 17] 1. Phenol route [17] Scheme 2.1 Reaction equation to produce paracetamol via the phenol route, reference [17] Scheme (2.1) represents the reaction equation to produce paracetamol via the phenol route. The reaction is done at under a temperature less than 0°C. The phenol and sodium nitrite solution is cooled to a temperature less than 0°C and then sulphuric acid is slowly added. After that the mass p-nitrosophenol is filtered, washed with water and reduced with sodium sulphide at 50°C. The resulted p-aminophenol is purified using hydrochloric acid with activated carbon. Then the synthesis of paracetamol was done using the obtained p-aminophenol with acetic anhydride [17]. 7 2. p-Nitrochlorobenzene route [17] Scheme 2.2 Reaction equation to produce paracetamol via the p-nitrochlorobenzene route, reference [17] Scheme (2.2) shows the reaction equation to produce paracetamol via the p-nitrochlorobenzene route. At a temperature of 160°C and 6 kg/cm3 pressure, the p-nitrochlorobenzene is hydrolyzed with sodium hydroxide. Then at 40°C the sodium salt of p-nitrophenol is reacted with sulphuric acid and then at 100°C with the addition of iron and acetic acid the p-nitrophenol is reduced. Afterwards, the reaction mass is filtered to get rid of iron sludge. The filtrate is cooled to 15°C and filtered again to get p-aminophenol. After the addition of acetic anhydride to p-aminophenol, the synthesis of paracetamol starts [17]. 8 3. Nitrobenzene route [5,17] Scheme 2.3 Reaction equation to produce paracetamol via nitrobenzene route, reference [5, 17] Scheme (2.3) explains the reaction equation to produce paracetamol via the nitrobenzene route. Nitrobenzene is treated catalytically in the presence of acid and then the mass is neutralized. The mass is distilled to get aniline and then treated with activated carbon to get pure p- aminophenol. The produced p-aminophenol is reacted with acetic anhydride in order to synthetize paracetamol [5, 17]. 11 2.9 Effect of impurities on the final product The use of additives to paracetamol in distinctive amounts has shown an impressive control on water content, crystal order & energy, dissolution rate and bioavailability [2]. Metacetamol’s main features are that it has an OH-group in the m-position and is a less effective blocker, while acetanilide has no para-group, no steric hindrance, no H- contribution and strongly blocks paracetamol. All in all, metacetamol is considered less effective than acetanilide as a blocker. Table (2.3) summarizes the differences between the two compounds [2]: By defining paracetamol as a drug, its solubility, the main synthetic routes and process related impurities, the science behind the first part of the continuous process has been explained and now a small introduction about crystallization and the effect of impurities on it will be given. Comparison / Compound Metacetamol Acetanilide Uptake level Higher Lower Degree of morphology Higher Appreciable Aspect ratio shift Higher Not available Table 2.3 Comparison between the effects of the impurities, reference [2] 12 2.10 Crystallization Crystallization is a separation technique that depends on the first-order transition phase between liquid and solid, which can be achieved by using a driving force to push the system away from equilibrium in a multicomponent liquid [10]. Industrial crystallization is the industrial process that’s used to investigate the product size, shape, particle size distribution & physical property. One of the major industrial challenges is controlling these properties which is necessary due to their important effect on powder flowability, bioavailability & solubilization. The importance of crystallization in the pharmaceutical industry is due to the opportunity of investigating the physiochemical properties of API with the ability to purify, improve and tailor its properties. To achieve the desired product quality, the crystallization conditions and the desired solid phase have to be clear. Defining the process condition and solid phase will give an insight into crystal morphology, habit and crystal size distribution (CSD) which all are connected to the quality characteristics of the product. Moreover, defining the process conditions means setting the system parameters from thermodynamics, kinetics, phase diagram and the phase transition kinetics [19]. 2.11 Crystal Nucleation Crystal nucleation is the first step in the crystallization process and happens usually in the supersaturated phase. This step defines the start of the crystalline solid phase and determines the number of crystals, crystal size distribution (CSD) and it might affect the type of crystalline material formed. Crystal formation can occur in two forms, primary and secondary nucleation. Primary nucleation usually occurs from a clear solution. Secondary nucleation can occur from the presence of parent crystals. However, primary nucleation is divided into homogeneous and heterogeneous nucleation. In heterogeneous nucleation, the crystals tend to form at the surface, such as walls and interfaces. Homogeneous nucleation happens from clear solution in the absence of heterogeneous nucleation [10]. 13 2.12 Crystal Growth Crystal growth or crystal growth rate is the indication for the (residence) time that it takes the crystal to grow to a specific size and shape in the crystallizer. Crystal growth rate depends on many factors which are: prevailing supersaturation in the solution, temperature, pressure, composition of the mother liquor, fluid flow conditions, crystal growth history and the presence of additives or impurities [10]. Precisely taking about the effect of impurities on the paracetamol crystal growth, previous studies have shown a significant change in the crystal properties of paracetamol. A change in the crystal shape was from prismatic to rectangular, triangular & rod-like, depending on the used additive [13]. 2.13 How can the impurities affect the crystal growth? The mechanism of impurities changing the crystal morphology or the crystal growth happens by impurities adsorbing unto the crystal surface, blocking the active sites and changing the surface free energy. The effect of impurities on the crystal growth varies among different types. It can be enhancing the growth, suppressing the growth entirely or producing a selective effect which can influence the levels of crystallographic surface and the crystal habit [2]. It has been observed that the presence of impurities effected crystallization properties and it can be generally summarized as follows: 1. It has an effect on the kinetics of crystal nucleation 2. Growth morphology and dissolution 3. Suppressing nucleation can be affected by the presence of soluble impurities [19]. The presence of acetanilide has shown the following effects on paracetamol crystal [2]: 1. Decreasing the crystallization rate 2. It alters the crystal habit 3. Increases the dissolution rate and surface area 4. Nucleation behavior [2] After explaining both processes the arising questions are why to switch to continuous manufacturing and what are the advantages of continuous manufacturing. 16 Table (3.2) represents the pipe types, sizes and manufactures that were used in the continuous set-up. Table (3.3) represents the devices that have been used with manufacturer name and device number. 3.2 Methods This section will explain the procedures that have been used to perform the designed experiments. 1. HPLC-Analysis The HPLC analysis was developed to detect paracetamol, 4-aminophenol, acetanilide, metacetamol and 4-nitrophenol concentration (throughout the reaction time). The samples were prepared by taking 100 µl sample diluted in 1 ml diluent of methanol 5%: HPLC-water 95% and were analyzed. Using an HPLC Agilent Technologies® model 1100 series. The device was equipped with an online degasser, quaternary pump, auto-sampler, thermostatic column compartment and UV-visible diode array detector. The mobile phase consists of methanol 5%: buffer 95%. The buffer was prepared from 0.05 M KH2PO4, pH 6 and 0.01 M CTAB (Cetyltrimethylammonium bromide) [13]. The stationary phase consisted of octadecyl- silylated silica gel Agilent Poroshell 120 EC-C18 reversed column, 2.7 µm particle size. Table 3.2 Pipe types, sizes and manufacturer for the continuous set-up Pipe type Pipe size (outer/inner diameter) Manufacturer Sillicon 4.8 x 2.4 mm Lactan® Sillicon 4 x 2 mm Lactan® PharMed 4 x 2 mm Lactan® Device Manufacturer Device model Water bath Lauda alpha® RA 12 Peristaltic pump Ismatec® ISM 833C Peristaltic pump Fischer scientific® GP 1100 Hotplate Heidolph® MR Hei-Standard Syringe pump HLL® LA 120 Hotplate IKA® C-MAG HS 7 HPLC Agilent Technologies® 1100 series Optical microscope Leica® DM 4000M Table 3.3 Devices that have been used with the manufacturer’s name and device number 17 The sample injection volume was 5 µl at 1 ml/min flowrate. The column temperature was 25°C and the UV-detector’s wavelength was 243 nm for 10 minutes run time. 2. HPLC-Analysis (Calibration curve) 1. Around 1.833 mmol of 4-aminophenol were dissolved in 100 ml methanol 5%: HPLC- water 95% solution (Usage of ultrasound is necessary). 2. 1 ml of the stoke solution has been taken and diluted with methanol 5%: HPLC-water 95% in 10 ml volumetric flask. The same procedure was done for 20, 25 and 50 ml volumetric flask with taking 1 ml from the stoke solution and diluted in methanol 5%: HPLC-water 95% solution. 3. Same steps were repeated for 4-nitrophenol, metacetamol, acetanilide and paracetamol. 3. Re-crystallization of 4-aminophenol 1. 412.35 mmol of p-aminophenol were dissolved in 370.55 ml of 6% phosphoric acid at 85°C in a 500 ml round bottom flask. 2. 1.435 mmol of sodium hydrosulfite were added to the solution and heated to 90°C, then 3.6 g of charcoal were added to the hot solution (the amount was calculated based on the available information in example 2, reference [11]) 3. The clear hot solution was decanted, filtered and treated with the charcoal using a Buchner funnel under vacuum. 4. The clear solution was left to cool down to room temperature under stirring. 5. To obtain the final white p-aminophenol crystals, the solution was filtered again. 6. The white crystals were collected and left to dry in a desiccator for one night under room temperature. (For this part, the crystallization dish should be covered in order to prevent the decomposing of p-aminophenol with light) [11] 18 4. The reaction of acetic anhydride with different solvents and impurities 0.966 mmol metacetamol were added to a 50 ml round bottom flask followed by 25 ml water and the mixture was stirred until everything was dissolved (the usage of ultrasound is necessary). When the whole amount was dissolved the first HPLC sample was taken, 100 µl sample was diluted in 1 ml of methanol: water (5:95) solution. Then 0.2 ml of acetic anhydride is added to the solution in the round bottom flask (a sample was taken). The solution was left to heat up to 40°C and a sample was taken every minute. After reaching the desired temperature the solution was kept under stirring for 15 minutes and a sample was taken every minute. For crystallization, the solution was cooled to 5°C for 30 minutes in the thermostat. Note: The same procedure was done with iso-amyl alcohol instead of water. Also, the same procedure was done for acetanilide (0.954 mmol) and 4-nitrophenol (0.956 mmol). 5. The synthesis of paracetamol with and without impurities This experiment was done with 4-aminophenol without impurities and with impurities. It has been tried 16 times, with different solvents, different amounts of acetic anhydride and the number of impurities was 4% of 4-aminophenol’s used amount. It is heating up the solvent to the desired temperature followed by the addition of 4-aminophenol and acetic anhydride together. An HPLC sample was taken immediately, after dissolving and at the end of the reaction. Samples were taken every minute (or at different time intervals) for further investigations. In the tests with impurities 4 mol% of each impurity were added to 4- aminophenol prior to the experiment. 6. Continuous set-up The continuous set-up parts, how it was built and the details to the different trials will be explained in details in section (4.10). 21 For the solubility data for paracetamol in 2-propanol (isopropyl alcohol) in figure (4.2), the experiment was also done with Crystalline® in Glasgow, Scotland, performed by a former visiting scientist to TU Graz Vaclav Svoboda from CMAC Glasgow, Scotland. The solubility data of paracetamol in 2-propanol couldn’t be performed at higher temperature than 60 °C due to low boiling point of the solvent. Conclusion & summary The aim of the solubility tests were to obtain a solubility profile over elevated temperature. The three solvents of interest in this thesis were water, iso-amyl alcohol and 2-propanol. Based on the solubility tests, which were carried out using Crystalline®, water and iso-amyl alcohol had low solubility at room temperature and higher solubility at elevated temperature. However, 2- propanol had a high solubility at room temperature and at elevated temperatures. 22 4.2 HPLC-Analysis (calibration curve) Calibration curves were obtained for 4-aminophenol, paracetamol, and the impurities (4- nitrophenol, metacetamol & acetanilide). The calibration curves were prepared as shown in table (4.1) and described in (Methods and Materials). Name Mw (g/mol) Mass (g) (g/ml) Theor. Conc. (mol/l) Dilution Ret. time (min) Peak area (mAU) Obtained Conc. (mmol/l) Actld 135.17 0.2212 0.0022 0.0164 Stock 4.164 37834.9 16.4 1:10 4.285 3966.4 1.60 1:20 4.290 2042.6 0.80 1:25 4.292 1645.2 0.60 1:50 4.300 821.9 0.30 4-NP 139.11 0.2749 0.0027 0.0198 Stock 5.636 11230.8 19.8 1:10 5.950 1082.4 2.00 1:20 5.987 554.6 1.00 1:25 5.995 442.8 0.80 1:50 6.014 221.5 0.40 MCM 135.11 0.2531 0.0025 0.0187 Stock 1.197 22296.2 19.6 1:10 1.227 3654.8 2.00 1:20 1.23 2045.1 1.00 1:25 1.23 3275.4 0.80 1:50 1.231 831.7 0.40 4-AP 109.13 0.1066 0.0011 0.0098 Stock 0.751 11944.9 9.8 1:10 0.997 1049.9 1.0 1:20 1.017 341.6 0.5 1:25 0.985 295 0.4 1:50 0.979 163.8 0.2 PCM 135.11 0.2531 0.0025 0.0187 Stock 1.197 24302.9 18.7 (with methanol:water (5:95) mobile phase) 1:10 1.227 3584 1.90 1:20 1.230 1788 0.90 1:25 1.230 1422 0.70 1:50 1.231 699 0.40 Table 4.1 Theoretical & experimental properties for the tested material in HPLC with methanol 5%: HPLC-water 95% mobile phase 23 For every compound, a stock solution was prepared and from this solution, a 1 ml amount was diluted in 10-20-25-50 ml of Methanol: water diluent separately. From every dilution, a 1 ml sample was transferred to HPLC vials in order to be tested. The retention times were almost the same for every dilution from the same material with ascendant concentrations and areas. The area for every solution was plotted to its concentration to get the calibration curve as observed in figure (4.3 & 4.4). Also, the calibration factor for every compound is available in table (4.2). y = 2E+06x R² = 0.999 0 1000 2000 3000 4000 5000 0.00000 0.00050 0.00100 0.00150 0.00200 A re a (m A U ) Concentration (mol/L) Acetanilide y = 551779x R² = 0.9995 0 500 1000 1500 0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 A re a (m A U ) Concentration (mol/L) 4-Nitrophenol y = 1E+06x R² = 0.999 -5000 0 5000 10000 15000 0.0000 0.0050 0.0100 0.0150 A re a (m A U ) Concentration (mol/L) 4-Aminophenol y = 1E+06x R² = 0.9902 0 5000 10000 15000 20000 25000 0.0000 0.0050 0.0100 0.0150 0.0200 0.0250 A re a (m A U ) Concentration (mol/L) Metacetamol Figure 4.3 Calibration curves for acetanilide, metacetamol, 4-nitrophenol & 4-aminophenol using 5%MeOH/95%H2O 26 The new graphs showed (figure (4.5)) linear trend and a regression of almost 1. The calibration factor values were almost the same as before as shown in table (4.4). The metacetamol and acetanilide calibration curve was obtained by preparing half amount from each compound and diluted in 100 ml diluent of methanol and water for HPLC. y = 2E+06x R² = 0.9952 0 1000 2000 3000 4000 0.0000 0.0005 0.0010 0.0015 0.0020 A re a (m A U ) Concentration (mol/L) Acetanilide y = 2E+06x R² = 0.9913 0 1000 2000 3000 0.0000 0.0005 0.0010 0.0015 A re a (m A U ) Concentration (mol/L) Metacetamol y = 2E+06x R² = 0.9945 0.0 1000.0 2000.0 3000.0 4000.0 0.0000 0.0005 0.0010 0.0015 0.0020 A re a (m A U ) Concentration (mol/L) Metacetamol + Acetanilide y = 1E+06x R² = 0.9842 0 500 1000 1500 0.0000 0.0005 0.0010 0.0015 A re a (m A U ) Concentration (mol/L) 4-Aminophenol Figure 4.5 New calibration curves for acetanilide, metacetamol, acetanilide and metacetamol & 4- aminophenol using 5% MeOH/95% buffer 27 Also for paracetamol, the regression was almost 1 as observed in figure (4.6). The calibration factors didn’t differ a lot from the old calibration factors as shown in table (4.4) but the HPLC column was safe and thus this method was implemented for further investigations although the 4-nitrophenol calibration curve couldn’t be obtained. Conclusion and summary The HPLC method using methanol 5%: HPLC-water 95% was successful to obtain all calibration curves but not safe enough for the column. The new method methanol 5%: buffer 95% was safe for the column but did not obtain the calibration curve for 4-nitrophenol. However, it was successful for 4-aminophenol, paracetamol, metacetamol and acetanilide. Compound Calibration factor ((mAU)* L/mol) Acetanilide 2000000 Metacetamol 2000000 Metacetamol + Acetanilide 2000000 4-Aminophenol 1000000 Paracetamol 2000000 Table 4.4 Calibration factors obtained from the mobile phase methanol 5%: buffer 95% Figure 4.6 New calibration curve for paracetamol using 5% MeOH/95% buffer y = 2E+06x R² = 0.999 0 500 1000 1500 2000 2500 3000 3500 0.0000 0.0002 0.0004 0.0006 0.0008 0.0010 0.0012 0.0014 0.0016 0.0018 A re a (m A U ) Concentration (mol/L) Paracetamol Figure 4.6 New calibration curve for paracetamol using 5% MeOH/95% buffer 28 4.3 Challenges with 4-aminophenol Before starting with the synthesis of paracetamol out of 4-aminophenol, solutions for 4- aminophenol challenges had to be found. The challenges are: decomposition by heat and light, high solid handling while pumping and impurities. The solution for high solid handling was milling of 4-aminophenol and obtaining a vibration feed rate instead of having the 4- aminophenol in suspension (for continuous set-up). The decomposition by heat & light and impurities challenges were solved by re-crystallization of 4-aminophenol experiment. Starting with milling 4-aminophenol, a liquid nitrogen was used while milling 4-aminophenol in a mortar and pestle. It was possible to do it with a mortar and pestle for small amounts but not for big amounts above 5 grams. For the vibration feeder, it was impossible to have a steady feeding rate due to the blocking of 4-aminophenol in the funnel opening. The re-crystallized 4-aminophenol experiment was built based on the US patent (no. 3,703,598 Nov. 21, 1972). The patent presents purification methods for the treatment of crude p- aminophenol and p-aminophenol obtained by reduction of nitrobenzene. Thus, to reduce the amount of 4-nitrophenol, black tars and color bodies. A combination between example 1 & 2 was done to obtain this section experimental procedure [7]. The recrystallization reaction components were done as in the table (4.5). (Procedure is available in chapter 3) Table 4.5 Batch trials for re-crystallization 4-aminophenol Batch number (1) (2) (3) Mass of charcoal (g) 0.3867 0.300 0.324 Mass of 4-AP 4.506 4.506 4.490 Mass of Na2S2O4 0.0248 0.0248 0.0247 Volume of phosphoric acid (ml) 37.055 37.055 37.055 Mass of re-crystallized 4-AP (g) 2.616 2.200 3.927 Yield % 58.055 48.823 87.266 31 As shown in table (4.6), the reaction was performed at 40 °C by heating up the water and then the addition of acetanilide and acetic anhydride. The reaction was left for 20 minutes and a sample was taken every minute. The reaction color was colorless and didn’t change with time. The samples didn’t show any crystals after cooling for one night in the fridge at 5°C. Table 4.6 Acetanilide reaction information with acetic anhydride in water Material Water Acetic Anhydride Acetanilide State Liquid Liquid Solid Mass (g) 25 - 0.128 Volume (ml) 25 0.2 - Molecular weight (g/mol) 18.02 102.09 135.17 Number of moles (mol) 1.39 0.002 0.001 Density (Total volume) [g/ml] 0.99 0.009 0.005 Concentration (Total volume) [mol/L] 55.07 0.08 0.04 Temperature (°C) 40 - - Reaction time (minute) 20 - - Color Clear solution 32 As presented in table (4.7), the first sample was taken at time 0. Immediately after the addition of acetanilide and acetic anhydride. Afterwards, a 100 µl sample was taken every minute. Then diluted with a 1 ml methanol: HPLC water diluent (5:95). Comparing the reaction information about acetanilide concentration in table (4.6 & 4.7) and figure (4.7), the concentration of acetanilide showed a constant values over time, thus apparently no reaction of acetanilide with acetic anhydride occurred. Table 4.7 Reaction sampling at different time intervals for acetanilide with acetic anhydride in water reaction Time (min) Sample weight (g) MeOH:H2O(g) Dilution factor Actld peak (mAU), tr= 3.266 (min) C Actld (mol/L) 0 0.10 1.03 11.82 8463.00 0.05 1 0.10 1.03 11.37 7673.00 0.04 2 0.10 1.03 11.11 8089.90 0.04 3 0.10 1.03 11.49 7925.20 0.05 4 0.10 1.05 11.76 7632.70 0.04 5 0.09 1.02 12.15 7460.10 0.05 6 0.10 1.01 11.30 8038.70 0.05 7 0.09 1.01 11.72 7774.80 0.05 8 0.10 1.01 11.22 8139.00 0.05 9 0.09 1.02 12.12 7385.70 0.04 10 0.04 0.92 22.50 3975.80 0.04 11 0.09 0.97 11.63 7634.60 0.04 12 0.10 0.89 10.31 8904.60 0.05 13 0.09 0.90 10.51 8565.30 0.05 14 0.10 0.99 11.39 8024.50 0.05 15 0.10 0.98 11.22 8064.10 0.05 16 0.09 0.99 11.53 7893.70 0.05 17 0.10 0.99 11.15 8201.60 0.05 18 0.09 0.98 11.43 7975.60 0.05 19 0.09 1.01 11.77 7766.70 0.05 33 From figure (4.7) it can be seen the constant concentration over time. Which means there was no reaction over time and thus acetanilide didn’t react with acetic anhydride. 0.000 0.010 0.020 0.030 0.040 0.050 0.060 0 5 10 15 20 C o n ce n tr at io n ( m o l/ L) Time (min) Acetanilide with (0.2 ml) AC2O in water Figure 4.7 Acetanilide concentration during reaction with acetic anhydride in water over time 36 4.4.2 Investigation of the reaction of metacetamol reaction with acetic anhydride in different solvents Metacetamol was chosen as the second impurity in order to check its reaction with acetic anhydride in different solvents. The expected outcomes are to investigate if there is a reaction between metacetamol and acetic anhydride. Also, to check if it will stay soluble after reaction or it will crystallize after cooling in fridge at 5°C for one night. 4.4.2.1 Investigation of the reaction of metacetamol reaction with acetic anhydride in water The first investigation for metacetamol was done with a molar ratio 2:1 of acetic anhydride in water. The aim of this experiment was to investigate metacetamol reaction and the crystallization in water after reaction. The reaction was carried out at 40 °C for 22 minutes and there was no change in color. The amount of metacetamol from HPLC was double in the amount comparing it with the theoretical concentration, given in table (4.10&4.11). Again that’s can be explained due to the inconveniently of the old mobile phase. Although, the difference between the theoretical and experimental amounts, the metacetamol concentration over time showed a constant behavior as presented in figure (4.9). Thus, apparently no reaction of metacetamol with acetic anhydride in water occured. Material Water Acetic Anhydride Metacetamol State Liquid Liquid Solid Mass (g) - - 0.144 Volume (ml) 25 0.2 - Molecular weight (g/mol) 18.02 102.09 151.16 Number of moles (mol) 1.39 0.002 0.001 Density (Total volume) [g/ml] 0.99 0.009 0.006 Concentration (Total volume) [mol/L] 55.05 0.08 0.04 Temperature (°C) 40 - - Reaction time (min) 22 - - Color Clear solution Table 4.10 Metacetamol reaction information with acetic anhydride in water 37 Time (min) Sample weight (g) MeOH:H2O(g) Dilution factor MCM peak (mAU), tr= 8.42 (min) C MCM (mol/L) 0 0.10 1.01 11.05 7145.1 0.08 1 0.10 1.01 11.40 6830.3 0.08 2 0.10 1.04 11.17 6955.8 0.08 3 0.10 1.01 11.28 7022.9 0.08 4 0.10 1.01 11.11 7086.6 0.08 5 0.10 1.01 11.27 6951.5 0.08 6 0.10 1.02 11.42 6807.4 0.08 7 0.19 1.02 6.28 12477.8 0.08 8 0.10 1.02 11.54 6922.9 0.08 9 0.10 1.02 11.37 7011.6 0.08 10 0.10 0.94 10.56 6880.7 0.07 11 0.09 1.01 11.91 6555.4 0.08 12 0.10 1.02 11.39 6875.2 0.08 14 0.09 1.02 12.26 6417.5 0.08 15 0.10 1.01 11.36 6926.9 0.08 16 0.10 1.01 11.30 7006.6 0.08 19 0.09 1.04 12.23 6857.2 0.08 20 0.09 1.03 11.86 6932.4 0.08 Table 4.11 Reaction sampling at different time intervals for metacetamol with acetic anhydride in water Figure 4.9 Reaction of metacetamol with acetic anhydride in water over time 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 5 10 15 20 25 C o n ce n tr at io n ( m o le /L ) Time (min) Metacetamol concentration vs time 38 4.4.2.2 Investigation of metacetamol reaction with acetic anhydride in iso- amyl alcohol In this experiment, the amount of acetic anhydride was increased with a molar ratio 20:1. The solvent was changed to iso-amyl alcohol with the same amounts of water. The reaction was carried out at 80 °C, stayed for 30 minutes and there was no change in color as shown in table (4.12). The amounts of metacetamol were almost constant with time. Some points showed fluctuation in amounts due to human error while sampling using the pipette (sample at time 16 min) as presented in table (4.13). However, most of the sample concentration showed constant values as shown in figure (4.10). Therefore, apparently there was no reaction between metacetamol and acetic anhydride in iso-amyl alcohol and even after cooling there was no presence for crystal formation. Table 4.12 Metacetamol reaction information with acetic anhydride in iso-amyl alcohol Material Isoamyl alcohol Acetic Anhydride Metacetamol State Liquid Liquid Solid Mass (g) - - 0.146 Volume (ml) 25 2 - Molecular weight (g/mol) 88.15 102.09 151.16 Number of moles (mol) 0.23 0.02 0.001 Density (Total volume) [g/ml] 0.75 0.08 0.005 Concentration (Total volume) [mol/L] 8.51 0.78 0.04 Temperature (°C) 80 - - Reaction time (min) 30 - - Color Clear solution 41 Time (min) Sample weight (g) MeOH: H2O(g) Dilution factor 4-NP Peak (mAU), tr= 8.42 (min) 4-NP Peak (mAU) , tr= 8.412 (min) 4-NP Peak (mAU), tr= 8.223 (min) 4-NP Conc., tr (8.420- 8.412) (min) 4-NP Conc., tr (8.420- 8.223) (min) 0 0.09 1.02 12.35 1796.8 - - 0.040 0.040 1 0.09 1.05 12.70 1679.4 - - 0.039 0.039 2 0.10 1.04 11.94 1734.1 - - 0.038 0.038 3 0.09 1.04 12.33 1679 - - 0.038 0.038 4 0.09 1.06 12.73 1685.4 - - 0.039 0.039 5 0.09 1.04 12.41 1680.2 - - 0.038 0.038 6 0.09 1.04 12.50 1683.8 - - 0.038 0.038 7 0.09 1.04 12.50 1737.9 - - 0.039 0.039 8 0.09 1.06 12.94 - 1164 438.1 - 0.038 9 0.09 1.05 12.44 - 1201 470 - 0.038 10 0.08 1.04 13.68 - 1013.9 467.5 - 0.037 11 0.09 1.05 13.00 - 1120.7 464.6 - 0.037 12 0.10 1.05 11.77 - 1230.9 511.9 - 0.037 13 0.10 1.05 12.01 - 1211.7 519.2 - 0.038 14 0.08 1.04 14.38 - 989.7 455.5 - 0.038 15 0.09 1.06 12.82 - 1110.8 509.5 - 0.038 16 0.09 1.04 12.16 - 1126.6 527.9 - 0.036 17 0.06 1.04 19.05 - 729.5 389.7 - 0.039 Table 4.15 Reaction sampling at different time intervals for 4-nitrophenol with acetic anhydride in water reaction 0.000 0.010 0.020 0.030 0.040 0.050 0.060 0 2 4 6 8 10 12 14 16 18 co n ce n tr at io n ( m o l/ L) Time (min) 4-Nitrophenol concentration vs time Figure 4.11 Reaction of 4-nitrophenol with acetic anhydride in water over time 42 4.4.3.2 Investigation of 4-nitrophenol reaction with acetic anhydride in iso- amyl alcohol The second experiment was with a molar ratio 20:1 acetic anhydride in the same amount of iso-amyl alcohol and 4-nitrophenol. As shown in table (4.16), the reaction was carried out at 80 °C for 22 minute and the color was light yellow and didn’t change with time. The concentration of 4-nitrophenol over time is shown in table (4.17) and figure (4.12). The obtained concentrations from HPLC showed higher concentration from the expected concentration and that’s cannot be reliable and it might be due to the instability of HPLC. Material Isoamyl alcohol Acetic Anhydride 4-Nitrophenol State Liquid Liquid Solid Mass (g) - - 0.132 Volume (ml) 25 2 - Molecular weight (g/mol) 88.15 102.09 139.11 Number of moles (mol) 0.23 0.02 0.001 Density (Total volume) [g/ml] 0.750 0.080 0.005 Concentration (Total volume) [mol/L] 8.51 0.78 0.04 Temperature (°C) 80 - - Reaction time (min) 22 - - Color Light yellow Time (min) Sample weight (g) MeOH:H2O(g) Dilution factor 4-NP peak (mAU), tr= 7.35 4-NP Conc. (mol/L) 0 0.07 1.00 16.03 219.0 0.006 2 0.07 1.01 14.47 278.0 0.007 7 0.07 1.00 15.25 278.9 0.008 22 0.08 1.01 14.07 237.0 0.006 Table 4.16 4-Nitrophenol reaction information with acetic anhydride in iso-amyl alcohol Table 4.17 Reaction sampling at different time intervals for 4-nitrophenol with acetic anhydride in iso-amyl alcohol 43 Conclusion The reaction of 4-nitrophenol with acetic anhydride in water and iso-amyl alcohol didn’t show any reaction and stayed in solution after cooling over night at 5 °C. Summary The investigations of impurities reaction (acetanilide, metacetamol and 4-nitrophenol) with acetic anhydride in different solvents (water and iso-amyl alcohol) didn’t show any reaction with different amounts of acetic anhydride in different solvents. Also, all the impurities stayed soluble after cooling in the fridge at 5 °C. 0.000 0.010 0.020 0.030 0.040 0 5 10 15 20 25 C o n ce n tr at io n ( m o l/ L) Time (min) 4-Nitrophenol concentration vs time Figure 4.12 4-Nitrophenol concentration with 2 ml acetic anhydride in water over time 46 4.5.2 Paracetamol synthesis without impurities in 2-Propanol The next chosen solvent is 2-propanol in which 4-aminophenol has a higher solubility in as shown in solubility data section. Therefore, different amounts of 4-aminophenol were used as well as acetic anhydride. Material 2-Propanol Acetic anhydride 4-Aminophenol State Liquid Liquid Solid Mass (g) 19.65 5.022 4.600 Volume (ml) 25 4.65 - Molecular weight (g/mol) 60.1 102.09 109.13 Number of moles (mol) 0.327 0.049 0.042 Density (Total volume)[g/ml] 0.663 0.169 0.155 Concentration (Total volume) [mole/L] 0.011 0.002 1.422 Density (solvent volume)[g/ml] 0.786 0.201 0.184 Concentration (solvent volume) [mol/L] 13.078 1.968 1.686 Mole equivalence 7.757 1.167 1.000 Temperature (°C) 60 - - Reaction time (min) 20 - - Color Light brown / light yellow Synthesis yield (%) 63.22 The reaction was carried out at 60 °C, for 20 minutes with color change from light brown to light yellow as presented in table (4.20). Table (4.21) shows the main aim of this reaction which was to investigate whether the 4-aminophenol will dissolve completely or not. Thus, only one sample was withdrawn after the 4-aminophenol was completely dissolved and at the end of the reaction. Also, the synthesis yield was 63.22%. Table 4.20 Paracetamol synthesis reaction information in 2-propanol with acetic anhydride Table 4.21 Reaction sampling at different time intervals for the synthesis of paracetamol in 2-propanol Time (min) Sample weight (g) MeOH:H2O(g) Total D.F PCM peak (mAU), tr= 1.19 (min) PCM Conc. (mol/L) 20 0.120 0.989 128.643 16570.1 1.066 47 4.5.3 Paracetamol synthesis without impurities in water In this experiment the used solvent is water, the reactants are acetic anhydride and 4- aminophenol without any impurities addition. The reaction was carried out at 80 °C, for 20 minutes with color change from light brown to light yellow as observed in table (4.22). The synthesis yield was 70.15% and only 2 samples were taken in the beginning of the reaction to investigate how long it takes 4-aminophenol to convert to paracetamol and it was 2 minutes as seen in table (4.23). Material Water Acetic anhydride 4-Aminophenol State Liquid Liquid Solid Mass (g) - - 1.80 Volume (ml) 25 1.80 - Molecular weight (g/mol) 18.015 102.09 109.13 Number of moles (mol) 1.388 0.019 0.016 Density (Total volume)[g/ml] 0.933 0.073 0.067 Concentration (Total volume) [mole/L] 51.781 0.711 0.615 Density (solvent volume)[g/ml] 1.000 0.078 0.072 Concentration (solvent volume) [mol/L] 55.509 0.762 0.660 Mole equivalence 84.135 1.154 1.000 Temperature (°C) 80 - - Reaction time (min) 20 Color Light brown / light yellow Synthesis yield (%) 70.15 Table 4.22 Paracetamol synthesis reaction information in water with acetic anhydride Time (min) Sample weight (g) MeOH:H2O(g) Total D.F PCM peak (mAU), tr= 1.19 (min) PCM Conc. (mol/L) 0 0.1847 1.6182 167.456 4196.4 0.351 2 0.1643 1.4169 153.540 6036.0 0.463 Table 4.23 Reaction sampling at different time intervals for paracetamol with acetic anhydride in water 48 Conclusion & Summary The aim from synthesis of paracetamol without impurities with acetic anhydride in different solvents to observe the full conversion of 4-aminophenol to paracetamol and the crystallization yield. Comparison between the synthesis yield from the previous reactions isn’t fair due to the difference between reaction times, the synthesis yield was calculated for iso-amyl alcohol (80.22%) after the reaction was done at 20 minutes, water (70.15%) was calculated after 2 minutes and 2-propanol (63.22%) after 20 minutes. 2-Propanol showed probably the lowest yield due to the higher temperature used in water and iso-amyl alcohol reaction. Based on the solubility data, the higher temperature the higher the solubility gets. Also, 2-propanol low boiling point was the prohibiting factor to increase its reaction temperature to 80 °C. For iso- amyl alcohol synthesis yield being higher than water, that can be explained due to the higher solubility of paracetamol in alcohols. 51 Figure (4.13) shows constant concentration of metacetamol and acetanilide over time. For paracetamol, figure (4.14) shows constant increase of the amounts over time. The synthesis yield was 83.2% which is higher than the synthetic reaction of paracetamol without impurities and that’s might be due to the addition of impurities or due to longer reaction time. . 0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800 0.900 0 2 4 6 8 10 12 14 16 18 P ar ac et am o l ( m o l/ L) Time (min) Paracetamol Concentration vs time Figure 4.13 Metacetamol + acetanilide concentration over time Figure 4.14 paracetamol concentration over time 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 0 2 4 6 8 10 12 14 16 18M et ac et am o l + A ce ta n ili d e (m o l/ L) Time (min) Metacetamol + Acetanilide concentration vs time 52 4.6.2 Paracetamol synthesis with impurities in water The second part of the paracetamol synthesis with impurities was in water as a solvent in different amount of acetic anhydride and 4-aminophenol. Part (1): Material Water Ac2O 4-AP 4-NP MCM Actld State Liquid Liquid Solid Solid Solid Solid Mass (g) 25.000 2.16 1.82 0.092 0.099 0.086 Volume (ml) 25.000 2.00 - - - - Molecular weight (g/mol) 18.015 102.09 109.13 139.11 151.16 135.17 Number of moles (mol) 1.39 0.02 0.02 0.0007 0.0007 0.0006 Density (Total volume)[g/ml] 0.93 0.08 0.07 0.0034 0.0037 0.0032 Concentration (Total volume) [mole/L] 51.40 0.78 0.62 0.02 0.02 0.02 Density (solvent volume)[g/ml] 0.93 0.09 0.07 0.0037 0.0040 0.0035 Concentration (solvent volume) [mol/L] 55.51 0.85 0.67 0.026 0.026 0.026 Mole equivalence 83.34 1.27 1.000 0.04 0.04 0.04 Temperature (°C) 80 Reaction time (min) 20 Color Brown/yellow Synthesis yield (%) 83.6 The reaction was carried out at 80 °C for 20 minutes. The reaction color changed from brown to yellow and the synthesis yield was 83.6% which is almost equivalent to the synthesis yield of iso-amyl alcohol in the previous section 83.28 %. Available information is given in table (4.26). Table 4.26 Paracetamol synthesis reaction information with impurities in water with acetic anhydride 53 Table (4.27) presents the concentration of paracetamol, metacetamol and acetanilide over time. The chosen samples to be tested in HPLC didn’t show good increasing values for paracetamol or constant for metacetamol and acetanilide. The reason of this instability, is the HPLC. Thus, there was not enough data to fit in a figure for this reaction. Part (2): The next reaction was performed using the recrystallized p-aminophenol with the same reaction amounts for the synthesis of paracetamol with acetic anhydride and impurities in water. The aim of this reaction was to investigate the recrystallized p-aminophenol behavior in reaction. Table (4.28) shows the reaction amounts for the re-crystallized 4-aminophenol and impurities with acetic anhydride in water, temperature was 40 °C, the paracetamol crystals color was white. The reaction took 18 minutes. Table 4.27 Reaction sampling at different time intervals for paracetamol and impurities with acetic anhydride in water No. Time (min) sample weight (g) MeOH: H2O(g) Total D.F PCM peak (mAU), tr= 1.2 (min) PCM conc. (mol/L) M+A peak (mAU), tr= 3.1 (min) M+A conc. (mol/L ) 5 12 0.104 1.012 120.87 9137.0 0.55 746.8 0.045 6 15 0.104 1.003 121.04 9321.5 0.56 761.4 0.046 56 Figure (4.15) shows paracetamol concentrations over time synthetized in water using the re- crystallized 4-aminophenol with impurities and acetic anhydride. The concentration got constant over time. Figure (4.16) shows the metacetamol and acetanilide concentrations over time in the reaction of re-crystallized 4-aminophenol with impurities and acetic anhydride in water. The concentrations were almost constant over the time. 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0 2 4 6 8 10 12 14 16 18 20 co n ce n tr at io n ( m o l/ L) Time(min) Paracetamol concentration vs time 0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0 2 4 6 8 10 12 14 16 18 20 co n ce n tr at io n ( m o l/ L) Time(min) Metacetamol + acetanilide concentration vs time Figure 4.15 Paracetamol concentrations in water over time using recrystallized 4-aminophenol Figure 4.16 Metacetamol + acetanilide concentrations in water over time using recrystallized 4- aminophenol 57 As presented in figure (4.17), an increasing amount of 4-aminophenol appeared in every sample. Which indicates there was no full conversion of the re-crystallized 4-aminophenol. Furthermore, investigations are needed to observe the nature of the synthetized material then repeating the investigation in synthesis for the production of paracetamol. The produced material needed further investigations with other analytical devises such as: FTIR. Conclusion Re-crystallization of 4-aminophenol experiments gave interesting results in synthesis but the appearance of 4-aminophenol through the run was enough to stop using the re-crystallized material. Thus, discovering the material nature with HPLC wasn’t enough and further analytical techniques are needed such as: FTIR or any other analytical method, such as NMR. 0.000 0.002 0.004 0.006 0.008 0.010 0 2 4 6 8 10 12 14 16 18 20 co n ce n tr at io n ( m o l/ L) Time(min) 4-Aminophenol concentration vs time Figure 4.17 4-Aminophenol concentrations in water over time using recrystallized 4-aminophenol 58 4.6.3 Paracetamol synthesis with impurities in 2-propanol In the third part of paracetamol synthesis with impurities, the chosen solvent was 2-propanol. The amount of it, is the same as the previous reactions. For 4-aminophenol and acetic anhydride, the amounts is higher based on the solubility data in section (4.1). The reaction was carried out at 60 °C, for 18 minutes with color change from brown to yellow and the synthesis yield was 89.21% as given in table (4.30). Material 2-Propanol (IPA) Ac2O 4-AP 4-NP MCM Actld State Liquid Liquid Solid Solid Solid Solid Mass (g) 19.65 5.044 4.097 0.2042 0.2304 0.2045 Volume (ml) 25.000 4.67 - - - - Molecular weight (g/mol) 60.10 102.09 109.13 139.11 151.16 136.17 Number of moles (mol) 0.327 0.049 0.038 0.001 0.002 0.002 Density (Total volume)[g/ml] 0.662 0.170 0.138 0.007 0.008 0.007 Concentration (Total volume) [mole/L] 11.020 1.665 1.265 0.049 0.051 0.051 Density (solvent volume)[g/ml] 0.786 0.202 0.164 0.008 0.009 0.008 Concentration (solvent volume) [mol/L] 13.078 1.976 1.502 0.059 0.061 0.061 Mole equivalence 8.7100 1.316 1.000 0.0391 0.0406 0.0403 Temperature (°C) 60 Reaction time (min) 18 Color Brown/yellow Synthesis yield (%) 89.21 Table 4.30 Paracetamol synthesis reaction information with impurities in 2-propanol with acetic anhydride 61 Table 4.33 Paracetamol synthesis and crystallization in water The synthesis yield was 96.96% which is the highest among all reactions. The crystallization yield was 87.73 % as given in table (4.33). The reason of the high yield might be there is no side reaction occurring. Material Water Ac2O 4-AP 4-NP MCM Actld State Liquid Liquid Solid Solid Solid Solid Mass (g) 25.000 2.16 1.808 0.095 0.0998 0.084 Volume (ml) 25.000 2.00 - - - - Molecular weight (g/mol) 18.015 102.09 109.13 139.11 151.16 135.17 Number of moles (mol) 1.39 0.02 0.02 0.0007 0.0007 0.0006 Density (Total volume)[g/ml] 0.93 0.08 0.07 0.0035 0.0037 0.0031 Concentration (Total volume) [mole/L] 51.40 0.78 0.61 0.025 0.024 0.023 Density (solvent volume)[g/ml] 1.00 0.09 0.07 0.0038 0.0040 0.0034 Concentration (solvent volume) [mol/L] 55.51 0.85 0.66 0.027 0.026 0.025 Mole equivalence 83.76 1.28 1.000 0.041 0.04 0.037 Temperature (°C) 80 Reaction time (min) 20 Color Yellow/white Synthesis yield (%) 96.96 Crystallization yield (%) 87.73 62 The concentration of metacetamol and acetanilide should start increasing because from previous experiments it stayed in solution and did not crystallize with time then after a certain time should show constant behavior. As shown in table (4.34) and figure (4.18) the amount of metacetamol & acetanilide started at 20 mmol/L concentration and increased to 40 mmol/L and maintained almost a constant concentration. For paracetamol, the concentrations decreased and then showed a constant concentration which is the solubility of paracetamol in water at 5°C. In figure (4.18), paracetamol concentration was decreasing over time. Thus 50 minutes seems to be enough for crystallization from 47°C to 5°C. Table 4.34 Sampling at different time intervals for paracetamol crystallization in water No. Time (min) T (°C) Sample weight (g) MeOH: H2O(g) Total D.F PCM peak (mAU), tr= 1.2 (min) PCM conc. (mol/L) M+A peak (mAU), tr= 3.2 (min) M+A conc. (mol/ L) 1 10 47 0.13 1.01 72.54 17683.2 0.64 639.7 0.02 2 20 37 0.10 1.01 90.48 10022.8 0.45 871.6 0.04 3 30 27 0.10 1.01 54.33 15232.2 0.41 1880.9 0.05 4 40 17 0.10 1.01 59.74 6805.0 0.20 1392 0.04 5 50 10 0.11 1.02 50.45 3148.6 0.08 773.6 0.02 6 60 5 0.10 1.01 81.12 3064.7 0.12 795.0 0.03 7 70 5 0.09 1.01 71.00 3257.1 0.12 975.7 0.03 8 80 5 0.10 1.01 139.36 1961.3 0.14 605.6 0.04 9 90 5 0.10 1.01 76.33 2839.5 0.11 920.1 0.04 10 100 5 0.10 1.01 65.59 3211.8 0.11 1038.6 0.03 11 110 5 0.12 1.01 106.61 2385.8 0.13 806.0 0.04 12 120 5 0.10 1.02 138.86 3581.8 0.25 1235.4 0.09 0.00 0.20 0.40 0.60 0.80 0 50 100 150 co n ce n tr at io n ( m o l/ L) Time (min) Paracetamol concentration vs time 0.00 0.20 0.40 0.60 0.80 1.00 0 50 100 150co n ce n tr at io n ( m o l/ L) Time (min) Metacetamol + acetanilide concentration vs time Figure 4.18 Paracetamol & metacetamol+ acetanilide concentrations in water over time during crystallization 63 4.7.2 Investigations of paracetamol crystallization in 2-propanol Same reaction conditions as in the synthesis were repeated in order to obtain the paracetamol crystallization data in 2-propanol. The reaction was carried out at 60 °C for 12 minutes, the synthesis yield was 86.39%, the crystallization yield was 63.61% and the crystal color changed from pink to white during crystallization as given in table (4.35). Table 4.35 Paracetamol synthesis and crystallization in 2-propanol Material 2-Propanol (IPA) Ac2O 4-AP 4-NP MCM Actld State Liquid Liquid Solid Solid Solid Solid Mass (g) 19.65 5.044 4.17 0.1967 0.2304 0.2028 Volume (ml) 25.000 4.67 - - - - Molecular weight (g/mol) 60.10 102.09 109.13 139.11 151.16 136.17 Number of moles (mol) 0.33 0.049 0.038 0.001 0.001 0.002 Density (Total volume)[g/ml] 0.662 0.170 0.141 0.007 0.007 0.007 Concentration (Total volume) [mole/L] 11.020 1.665 1.288 0.048 0.049 0.051 Density (solvent volume)[g/ml] 0.786 0.202 0.167 0.008 0.009 0.008 Concentration (solvent volume) [mol/L] 13.078 1.976 1.528 0.059 0.058 0.061 Mole equivalence 8.558 1.293 1.000 0.037 0.038 0.039 Temperature (°C) 60 Reaction time (min) 12 Color Pink/white Synthesis yield (%) 86.39 Crystallization yield (%) 63.61 66 4.7.3 Investigations of crystallization kinetics in iso-amyl alcohol The amounts and reaction conditions were repeated for the synthesis of paracetamol in iso- amyl alcohol. As shown in table (4.37), the reaction was carried out at 80 °C for 23 minutes with change in color from yellow to white, the synthesis yield was 65.97% and the crystallization yield was 31.22%. The low values of synthesis yield might be due to side reactions. For crystallization yield, although the solubility data showed lower solubility of paracetamol in iso-amyl alcohol at lower temperature, still there is a high concentration of paracetamol in iso-amyl alcohol at low temperature. Comparing the concentrations with water, water showed a better solvent for crystallization. Material Iso-amyl alcohol Ac2O 4-AP 4-NP MCM Actld State Liquid Liquid Solid Solid Solid Solid Mass (g) 20.250 3.11 2.65 0.129 0.140 0.135 Volume (ml) 25.000 2.88 - - - - Molecular weight (g/mol) 88.148 102.09 109.13 139.11 151.16 136.17 Number of moles (mol) 0.230 0.030 0.024 0.001 0.001 0.001 Density (Total volume)[g/ml] 0.727 0.111 0.095 0.005 0.005 0.005 Concentration (Total volume) [mole/L] 8.249 1.083 0.87 0.033 0.033 0.04 Density (solvent volume)[g/ml] 0.810 0.123 0.106 0.005 0.005 0.0054 Concentration (solvent volume) [mol/L] 9.189 1.22 0.97 0.037 0.036 0.04 Mole equivalence 9.47 1.300 1.000 0.040 0.040 0.040 Temperature (°C) 80 Reaction time (min) 23 Color Yellow/white Synthesis yield (%) 65.97 Crystallization yield (%) 31.22 Table 4.37 Paracetamol synthesis and crystallization in iso-amyl alcohol 67 In order to have a nice trend for the concentration of paracetamol over time, the samples at time (30, 70 & 80 min) were deleted. Because sample at time (10 min) had human error and samples at time (70 & 80 min) had unstable peak from HPLC. The used data in figure (4.21 & 4.22) are presented in table (4.38). Figure (4.21) shows paracetamol concentration over time in iso-amyl alcohol while crystallization. The paracetamol concentration over time did not show decreasing but constant concentration over time. It showed constant trend from the first sample. This might indicate to the solubility of paracetamol in iso-amyl alcohol is not low like in water and a certain concentration will be soluble after time, although as soon as the temperature reaches 5°C, at time (50 min), crystals where formed. 0.00 0.20 0.40 0.60 0.80 1.00 1.20 0 20 40 60 80 100 120 140C o n ce n tr at io n ( m o l/ L) Time (min) Paracetamol concentration vs time Table 4.38 Sampling at different time intervals for paracetamol crystallization in iso-amyl alcohol No. t (min) T (°C) Sample weight (g) MeOH: H2O(g) Total D.F PCM peak (mAU), tr= 1.2 (min) C PCM (mol/ L) M+A peak (mAU), tr= 3.2 (min) C M+A (mol/L) 1 10 47 0.0958 1.00 101.38 12710 0.64 763.7 0.04 2 20 43 0.0957 1.00 125.01 10550.6 0.66 658.7 0.04 4 40 18 0.0903 1.00 117.31 10866.8 0.64 684.5 0.04 5 50 5 0.0841 0.99 148.29 9150.2 0.68 621.4 0.05 6 60 5 0.0913 0.99 100.95 10547.4 0.53 629.9 0.03 9 90 5 0.0868 0.95 142.12 9542.6 0.68 706.4 0.05 10 100 5 0.0940 0.93 105.81 11859.3 0.63 906.5 0.05 11 110 5 0.0901 1.01 138.47 7746.8 0.54 602.7 0.04 12 120 5 0.0930 1.01 110.23 10533.8 0.58 807.6 0.04 Figure 4.21 Paracetamol concentrations in iso-amyl alcohol over time during crystallization 68 For the metacetamol & acetanilide concentration, it doesn’t show constant behavior. However, taking a deep look into the data and taking samples at time (10, 20, 40, 50, 60, 90, 100,110 & 120 min), figure (4.22) showed a constant behavior which is the main goal from the test. Conclusion & summary The aim from repeating the synthesis and crystallization of paracetamol with impurities and acetic anhydride in different solvents is to investigate the crystallization of paracetamol over time. Paracetamol was crystallized in all solvents however the highest synthesis & crystallization yield was for water > 2-propanol > iso-amyl alcohol and that’s due to the low solubility of paracetamol in water at 5°C more than 2-propanol and iso-amyl alcohol. The table below (4.39), shows a comparison between the synthesis and crystallization yield of paracetamol in the three solvents (water, iso-amyl alcohol & 2-propanol). For the synthesis, it might differ from the previous experiment due to HPLC instability or human error while sampling. Solvent Synthesis yield (%) Crystallization yield (%) Water 96.96 87.73 2-propanol 86.27 63.61 Iso-amyl alcohol 65.97 31.22 Table 4.39 Synthesis and crystallization yield comparison among different solvents Figure 4.22 Metacetamol + acetanilide concentration in iso-amyl alcohol over time during crystallization 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 0 20 40 60 80 100 120 140 C o n ce n tr at io n ( m o l/ L) Time (min) Metacetamol +acetanilide concentration vs time 71 Second procedure: In this part, the reason behind not diluting is the absence of impurities and there was no risk on the HPLC column. As mentioned before, it was simple preparations which consist of dissolving 0.5 mg of the crystals in 2 ml of the diluent methanol: HPLC-water (5:95) in HPLC vial then diluted and filtered with a 0.2 µm higher again. (Experiments from section 4.5) The synthetic reaction of paracetamol without impurities with acetic anhydride in water gave light pink crystals after crystallization and only paracetamol peak appeared in the HPLC. The synthesis yield was 70.15% and the crystallization yield was 71.07% as given in table (4.43). The higher percentage of crystallization is due to the filtration technique and inefficient drying. The synthetic reaction of paracetamol without impurities with acetic anhydride in 2-propanol gave white crystals and only paracetamol peak in the HPLC. The synthesis yield was 63.22% and the crystallization yield was 65.40 %, crystallization yield is higher than synthesis due to the filtration technique and water content. Information are given in table (4.44). Table 4.43 Crystal purity test information for the paracetamol synthesis without impurities with acetic anhydride in water Reaction information Water, without impurities Amount 0.5 mg crystal, 2 ml water/methanol Synthesis yield (%) 70.15 Crystallization yield (%) 71.07 Total dilution factor (-) 24882.878 Area (mPa) 663.6 Crystal color Light pink Mass of sample (g) 0.187 Mass of diluent (g) 1.438 Table 4.44 Crystal purity test information for the paracetamol synthesis without impurities with acetic anhydride in 2-propanol Reaction information 2-propanol, without impurities Amount 0.5 mg crystal, 2 ml water/methanol Synthesis yield (%) 63.22 Crystallization yield (%) 65.40 Total dilution factor (-) 17246.521 Area (mPa) 1520.4 Crystal color White Mass of sample (g) 0.13 Mass of diluent (g) 0.989 72 The synthetic reaction of paracetamol without impurities with acetic anhydride in iso-amyl alcohol gave white crystals. The synthesis yield was 80.22% and the crystallization yield was 57.60 %, it’s considered to be low compared to the other solvents results. Results described in table (4.45). Third procedure: The third procedure of crystal purity investigations was done by diluting 10 mg of crystals in 100 ml diluent then diluting 100 µl in 1 ml of diluent then filtration. (Experiments from section 4.7) The given information’s in table (4.46) represent synthetic reaction of paracetamol with impurities and acetic anhydride in water (investigation of paracetamol crystallization). The synthesis yield was 96.96% and the crystallization yield was 87.73%, the difference between the two yields is due to an error while filtration and drying. The crystal color was yellow and the HPLC showed only peaks for paracetamol. However, the yellow color of the crystals might indicate a presence for the impurity 4-nitrophenol. Table 4.45 Crystal purity test information for the paracetamol synthesis without impurities with acetic anhydride in iso-amyl alcohol Reaction information Iso-amyl alcohol, without impurities Amount 0.5 mg crystal, 2 ml water/methanol Synthesis yield (%) 80.22 Crystallization yield (%) 57.60 Total dilution factor (-) 18413.432 Area (mPa) 186.8 Crystal color White Mass of sample (g) 0.1 Mass of diluent (g) 1.01 Table 4.46 Crystal purity test information for the paracetamol synthesis with impurities & acetic anhydride in water with impurities Reaction information Water, with impurities Amount 10 mg crystal, 100 ml water/methanol Synthesis yield (%) 96.96 Crystallization yield (%) 87.73 Total dilution factor (-) 74510.76 Area (mPa) 143.8 Crystal color Yellow Mass of sample (g) 0.15 Mass of diluent (g) 1.00 73 The synthetic reaction of paracetamol with impurities and acetic anhydride in 2-propanol (investigation of paracetamol crystallization in 2-propanol) showed light pink crystals with only paracetamol peaks in the HPLC. The synthesis yield was 86.27% and the crystallization yield was 63.61% as given in table (4.47). Synthesis yield is higher than crystallization due to the high solubility of paracetamol in 2-propanol. The synthetic reaction of paracetamol with impurities and acetic anhydride in iso-amyl alcohol (investigation of paracetamol crystallization in iso-amyl alcohol) showed light yellow crystals with only paracetamol peaks in the HPLC. The synthesis yield was 65.97% and the crystallization yield was 31.22%, for both yields it’s considered low. For synthesis, it can be explained for the side reaction occurrence. For crystallization, due to the high solubility of paracetamol in iso-amyl alcohol at 5°C. However, the yellow color can indicate to an impurity presence. Information is given in table (4.48). Table 4.47 Crystal purity test information for the paracetamol synthesis with impurities & acetic anhydride in 2-propanol Reaction information 2-propanol, with impurities Amount 10 mg crystal, 100 ml water/methanol Synthesis yield (%) 86.27 Crystallization yield (%) 63.61 Total dilution factor (-) 70876.86 Area (mPa) 1524.0 Crystal color Light pink Mass of sample (g) 0.162 Mass of diluent (g) 1.002 Table 4.48 Crystal purity test information for the paracetamol synthesis with impurities & acetic anhydride in iso-amyl alcohol Reaction information Iso-amyl alcohol, with impurities Amount 10 mg crystal, 100 ml water/methanol Synthesis yield (%) 65.97 Crystallization yield (%) 31.22 Total dilution factor (-) 90085.69 Area (mPa) 151.5 Crystal color Light yellow Mass of sample (g) 0.124 Mass of diluent (g) 1.01 76 Also, the crystals obtained from 2-propanol (shown in figure (4.25)) had a prismatic to round particle shape. Conclusion Based on the microscopic images, the most round shaped particles were obtained from water > 2-propanol > iso-amyl alcohol. Having round shape particles is important for further processes. Figure 4.25 Crystals from the synthesis with impurities in 2-propanol 77 4.10 Continuous set-up The aim for building the continuous set-up was to couple the synthesis part with the crystallization part based on the collected parameters and information from the previous explained batch investigations. The used HPLC method was methanol 5%: buffer 95% solution because it didn’t harm the column although it wasn’t applicable to obtain the 4-nitrophenol peak. From the batch experiments, the investigations of impurities behavior showed no reaction with acetic anhydride in any solvent and all of them were soluble in solution after crystallization. The investigations of 4-aminophenol with and without impurities showed that the highest crystallization yield was obtained using water as a solvent with 20 mmol acetic anhydride. Higher temperatures didn’t show any improvement to the reaction. Thus, the starting points for the continuous set-up were: the reaction at 40°C, the experiment from the investigation of paracetamol synthesis with impurities in acetic anhydride with water will be scaled-up to the continuous set-up reactor volume with synthesis time 20 minute pumping with 1.6 ml/min flowrate for acetic anhydride pump, 20 ml/min for the solid suspension pump. For crystallization, the time will be 20 minute with 21.6 ml/min flowrate. Scheme 4.1 Schematic diagram for the continuous process for integrated synthesis and crystallization of paracetamol 78 As shown in scheme (4.1), tank (1) had water, 4-aminophenol and impurities at 25°C pumped with a peristaltic pump (GP 1000) to the synthesis reactor (CSTR Vmax=400 ml) using silicon pipe with 4.8x2.4 mm (outer/inner diameter) with 20ml/min flow rate. The synthesis reactor was covered by a GL 18 and heated up with water bath to 40°C. For the acetic anhydride, it was pumped using a syringe pump (represented in the scheme as tank (2)) to the synthesis reactor with 1.6 ml/min flow rate. From the synthesis reactor to the crystallization reactor (CSTR Vmax= 400ml) a peristaltic pump Ismatec type was used with silicon type 4x2 mm (outer/inner diameter) with 21.6ml/min flow rate. The crystallizer was covered with GL 18 cover and cooled with water bath 5°C. Using another peristaltic pump Ismatec type with silicon type 4x2 mm (outer/inner diameter) the crystallized paracetamol was pumped into a Buchner funnel for filtration with 21.6 ml/min flow rate. More details about the manufacturers of equipment’s and material are mentioned in chapter 3. Table (4.50) shows the batch experiment used amounts and the scaled- up that was used in the synthesis reactor. The scale-up factor was calculated by dividing by the full CSTR reactor volume (Vmax = 400 ml) over the batch volume. These number were used in the trials (1 and 2). Table 4.50 Materials and amounts that are used in the continuous set-up for 1 residence time Entity Amounts in batch scale Amounts for Vr=400 ml scale up factor water 25 ml 400 ml 16 Ac2O 2 ml 32 ml 4-AP 1.808 g 28.928 g 4-NP 0.0953 g 1.5248 g Acetanilide 0.0839 g 1.3424 g Metacetamol 0.0998 g 1.5968 g Table 4.51 Materials and amounts that are used in the continuous set-up for 2.5 residence time Entity Amounts batch scale Amounts in Vr=1000 ml scale up factor water 25 ml 1000 ml 40 Ac2O 2 ml 80 ml 4-AP 1.808 g 72.32 g 4-NP 0.0953 g 3.812 g Acetanilide 0.0839 g 3.356 g Metacetamol 0.0998 g 3.992 g 81 Figure (4.26) shows the step-wise set-up for the synthesis and crystallization of paracetamol. The picture on the left represents the synthesis set-up which was built first and the product from it was stored in the fridge overnight for the next day. The picture on the right represents the crystallization set-up which was built next day from the synthesis set-up. The product was heated up to 40°C in order to simulate the synthesis temperature. The crystallization reactor was cooled to 5°C. Figure 4.26 Trial (1) step-wise set-up for the synthesis and crystallization of paracetamol Tank (1) Syringe pump Synthesis reactor Peristaltic pump Crystallization reactor 82 Trial (2): This trial was done step-wise by starting with the synthesis part then with the crystallization part to make sure if the available pipes can withstand through the process. The starting amounts for the tank (1) given in table (4.51) and the starting amounts for the synthesis reactor given in table (4.50). Figure (4.27) shows the set-up for the step-wise synthesis and crystallization of paracetamol in trial (2). The reaction was performed at 40°C for the synthesis and 5°C for crystallization. Figure 4.27 Step-wise set-up for the synthesis and crystallization of paracetamol trial (2) Synthesis reactor Peristaltic pump Syringe pump Tank (1) Peristaltic pump Crystallization reactor 83 For the synthesis part, thirteen samples were withdrawn during the reaction by detaching the peristaltic pump tube from the GL 18 cover. The cover was tighten with para film in order to detach it easily. Each sample was taken after five minutes. In table (4.54), ST is the sample taken from tank (1), SR is the sample taken from the synthesis reactor at time 0 and SRf is the sample taken from the reactor after the end of the experiment. Table 4.54 Sampling at different time intervals for the synthesis of paracetamol using continuous set-up No. t (min) T (°C) Sample weight (g) MeOH: H2O (g) Total D.F Area PCM (mAU), tr= 1.2 (min) PCM conc. (mol/L ) Area M+A, tr= 3.2 (min) M+A conc. (mol/L ) 1 ST 25 0.1 1.0 103.7 12.9 0.00 1192.9 0.06 2 SR 40 0.1 1.0 244.7 0 0.00 1685.2 0.21 3 5 40 0.1 1.0 86.0 437.6 0.02 1856.2 0.08 4 10 40 0.1 1.0 60.0 1153.8 0.03 2134.6 0.06 5 15 40 0.1 1.0 115.0 1744 0.10 815.2 0.05 6 20 40 0.1 1.0 47.6 6960.2 0.17 2678.6 0.06 7 25 40 0.1 1.0 47.3 7606.9 0.18 2286.2 0.05 8 30 40 0.1 1.0 84.7 4884.6 0.21 1423.8 0.06 9 35 40 0.1 1.0 82.7 4208.3 0.17 1237.3 0.05 10 40 40 0.1 1.0 86.7 4004 0.17 1207.7 0.05 11 45 40 0.1 1.0 50.2 6271.8 0.16 1726.1 0.04 12 50 40 0.1 1.0 67.8 5630.7 0.19 1711.9 0.06 13 SRf 40 0.1 1.0 88.5 4120.6 0.18 1116.7 0.05