Equipment and Techniques for Distillation and Extraction Processes in Organic Chemistry, Slides of Electrical Engineering

Download Equipment and Techniques for Distillation and Extraction Processes in Organic Chemistry and more Slides Electrical Engineering in PDF only on Docsity! Organic Chemistry a selection of typical applications Distributed By: Camlab Limited, Camlab House, Norman Way Industrial Estate, Over, Cambridge CB24 5WE, UK E - sales@camlab.co.uk T - +44 1954 233110 • Quickfit; a system of individual components produced from borosilicate glass, that feature interchangeable ground glass joints which can be combined together to create assemblies for chemistry experiments. Definition Reflux Preparation or recovery Reflux with stirring and drying Reflux with Addition • A reactant is added to the refluxing reaction mixture in a controlled way via either a traditional dropping funnel and a venting piece, such as a stillhead for example or a pressure equalising dropping funnel • This technique is used to prevent exothermic reactions from getting out of control Dropping funnel Stillhead What you need • Stillhead • Dropping funnel Distillation • Distillation is the process of separating components of liquid mixtures through vaporisation and condensation, based on different volatility or boiling points of components in the mixture • Distillation is a physical separation process, and not a chemical reaction • This technique is used for purification • This is a simple distillation assembly What you need • Flask – pear or round bottom, capacity should be approximately double the flask contents. • Condenser – Liebig or Davis in horizontal alignment • Stillhead • Receiver • Thermometer and thermometer adapter • Heat source – Bunsen burner, water bath, heating mantle or hot plate Thermometer Thermometer adapter Receiver • Vacuum distillation is a distillation carried out at reduced pressure to lower boiling points • Using a magnetic stirrer bar prevents the liquid from ‘bumping’ when under vacuum Vacuum Distillation magnetic stirrer bar Round bottom Flask Angled vacuum receiver What you need • Flask – pear or round bottom, capacity should be approximately double the flask contents. • Condenser – Liebig • Stillhead • Angled vacuum receiver • Thermometer and thermometer adapter • Heat source – Bunsen burner, water bath, heating mantle or hot plate • The extraction of a crude mixture containing water-insoluble material (such as natural products) can be achieved by the co- distillation with steam • The dropping funnel is filled with water and added to the distillation to maintain the level of water in the distillation flask • The distillate is collected in a conical flask and the product can be separated from the water using a separating funnel or by solvent extraction Steam Distillation Claisen stillhead adapter Dropping funnel What you need • Flask – round bottom, capacity should be approximately double the flask contents. • Condenser – Liebig or Davis in horizontal alignment • Claisen stillhead adapter • Receiver • Thermometer and thermometer adapter • Heat source – Bunsen burner, water bath, heating mantle or hot plate • A technique to remove a volatile product from a reaction mixture to prevent further reaction taking place • There are many reactions that yield products which themselves can undergo further reaction • One such example is the oxidation of primary alcohols with acidified chromate (VI) which will yield an aldehyde which can be oxidised further to a carboxylic acid • The aldehyde has a lower boiling point than the alcohol so it can be removed by distillation as soon as it is formed Distillation of a Volatile Product Thermometer and thermometer adapter Two neck round bottom flask Extraction • Extraction is a separation process consisting in the separation of a substance from a matrix • There are two types of extraction: • Liquid-liquid extraction • Solid-liquid extraction Rotary Evaporation • A rotary evaporator is used to remove large amounts of solvent from solutions at a reduced pressure • This is often done to isolate a product from a chromatographic separation or a solvent extraction. • Rotary evaporators feature a thermostatically controlled water bath and a vacuum to create conditions to evaporate solvents within a system of reduced pressure • A key disadvantage in rotary evaporations is the potential of some sample types to foam or bump, which can result in loss of a portion of the material intended to be retained. Even professionals experience periodic mishaps during evaporation, especially bumping • Rotary evaporators can also be equipped with further special traps called splash heads, that are best suited to particular difficult sample types, including those with the tendency to foam or bump. • SciLabware produces evaporation flasks and accessories that are compatible with a wide selection of rotary evaporator manufactures • Evaporation flasks • Florentine flasks • Round bottom flasks • Splash head • Anti-climb • With sinter • Splash heads reduces entrainment of raw liquid into the vapour stream, protecting the condenser against liquid ingress from liquids that have tendency to foam or bump Florentine flask Splash head Rotary Evaporation Recrystallisation • Reactions often yield impure products which need to be purified by recrystallisation. • The impurities present can be side products of the reaction, unreacted starting materials as well as insoluble impurities such as anti- bumping granules • By dissolving both impurities and a compound in a minimum amount of suitable hot solvent • Immediate filtration of the hot mixture removes any insoluble impurities • The filtrate solution is then to cool allowing crystals of the purified product to form • The last step is the collection of the product by filtration Filtration • Filtration is the mechanical or physical operation used for the separation of solids from fluids by interposing a medium through which only the fluid can pass. • The fluid that passes through is called the filtrate. • If the solid is to be discarded it is done by gravity filtration • If the solid is to be collected it is done under a reduced pressure using a Büchner Funnel and Büchner Flask Filtration: Gravity Filtration • Gravity filtration is generally carried out to remove impurities rather than to isolate solids What you need • Beakers • Stirring rod • Conical flask • Filter funnel • Filter papers • Retort stand • Metal ring to support funnel • This is the simplest kind of filtration when the solution to be filtered is poured through a filter paper in a filter funnel • The filtration of hot solutions through a heated funnel and fluted filter paper is often carried out as part of a recrystallisation Filtration: Büchner Filtration • When a solid needs to be isolated from a solution it is normally done at a reduced pressure using a Büchner flask and Büchner funnel What you need • Beakers • Stirring rod • Büchner flask • Büchner funnel • collar • Filter papers • Retort stand • Metal clamp • The technique of Thin Layer Chromatography (TLC) is normally used as an analytical method to follow the progress of a reaction, to analyse mixtures or to establish conditions for a preparative separation of compounds using column chromatography Thin Layer Chromatography • The stationary phase (often silica) is coated on plastic or aluminium plates • The mixture is spotted on the plate and solvent is allowed to run up the plate and separate the compounds PYR Thin Layer U.K. EX QUICKFIT® Thin Layer Chromatography (TLC) is used to analyse reaction mixtures and establish solvent systems to be used for column chromatography. Like column chromatography, TLC relies on the difference in affinities for various compounds for the stationary phase (often silica) and the solvent used as the mobile phase. As the mobile phase (solvent) moves up the plate each . component is carried at a different rate. . Because the plates are treated with a fluorescing agent, observing the plate under UV light shows the separated components as dark spots. fo Chromatography [ TLC plate is positioned inside the development tank When the solvent reaches the top end ° ° of the plate, the plate is removed from the . beaker and the solvent allowed to h 86 evaporate. Dean-Stark Apparatus • There are many equilibrium reactions that yield water as a co-product where removal of the water as it is produced is necessary to drive the reaction to completion and this is done using a Dean-Stark pattern water estimator. • The reaction is carried out under reflux in a solvent which is less dense than water, both immiscible with it and forms an azeotrope. • The apparatus allows the water to be separated from the condensed azeotrope preventing it from returning to the reaction mixture. Dean-Stark pattern water estimator The azeotrope condenses and fills the burette, the more dense water separating and falling to the bottom What you need • Round bottom flask • Dean-Stark pattern water estimator • Condenser Titration: Application • Titrations are performed to determine the concentration of a solution by reacting it with an accurately prepared standard solution. • The most common titration is that of an acid with a base, for which an indicator is necessary. Titration: Application • A sample of the unknown solution is transferred to a conical flask using volumetric pipette. • This sample is known as the ‘aliquot’. • At this stage a suitable indicator is added Titration: Application • The standard solution is added to the burette, the initial reading is taken and then the titration can be carried out.