Amines and Amides: Organic Nitrogen Compounds | CH 105, Lab Reports of Chemistry

Download Amines and Amides: Organic Nitrogen Compounds | CH 105 and more Lab Reports Chemistry in PDF only on Docsity! CH105 Lab 19: Amines & Amides 245 LAB 19: AMINES & AMIDES: ORGANIC NITROGEN COMPOUNDS PURPOSE: To investigate the properties of amines and their salts. To study properties of quinine. To perform basic hydrolysis of an amide. SAFETY CONCERNS: Always wear safety goggles. Amines have pungent odors. Avoid skin contact with aniline, a skin irritant and deadly poison. Wash your hands after use. . AMINES: Structure and Classification of Amines: Amines are derivatives of ammonia, NH3, in which one or more hydrogen atoms of ammonia have been replaced by an organic group. They are classified as primary, secondary, or tertiary, according to the number of groups attached to the nitrogen. NH3 CH3 N H H CH3 N H CH3 CH3 N CH3 CH3 Ammonia Methylamine (primary, 1o) Dimethylamine (secondary, 2o) Trimethylamine (tertiary, 3o) Amines are often found as part of compounds that are physiologically active or used in medications. OH N CH3 H HO N N NH2H N CH3 H CH3 Neo-Synephrine Histamine Methamphetamine NH2 Aniline CH105 Lab 19: Amines & Amides 246 Amines in Water: In water, ammonia and soluble amines (with one to four carbons) act as weak bases because the unshared pair of electrons on the nitrogen atom attracts protons. The products are an ammonium ion or alkyl ammonium ion and a hydroxide ion. + H2O OH Ammonia Water Ammonium ion + Hydroxide Ion CH3 N H H + H2O CH3 N H H H OH Methylamine Water Methylammonium ion + Hydroxide Ion N H HH N H H H H Neutralization of Amines with Acids: Because amines are basic they react readily with acids to form salts. Amine salts are much more soluble in water than the corresponding amines. CH3 N H H + HCl CH3 N H H H Cl Amine Base Acid Amine Salt Amines (free bases) may be regenerated from the salt by treatment with a base such as sodium hydroxide. + NaOHCH3 N H H H Cl Amine BaseAmine Salt + +CH3 N H H H2O NaCl ALKALOIDS: Alkaloids are naturally occurring nitrogen compounds having pronounced physiological activity. Like other simpler amines, alkaloids and bases; the name alkaloid comes from their alkaline properties. These complex molecules come from plants and many have medical uses. They are generally insoluble in water, and are often found in commercial products in the form of their water-soluble acid salts. + Alkaloid Acid Salt (water soluble) Alkaloid (water insoluble) Acid The pure alkaloid (in its “free base” form) can be obtained as a precipitate from its acid salt by treatment with a base such as sodium hydroxide. CH105 Lab 19: Amines & Amides 249 Amide Preparation: Amides can be synthesized by several methods. When a carboxylic acid reacts with a basic amine an amine salt forms. When amine salts are heated it is possible to drive off water to form amide bonds. CH3 C O O H + H N H CH3 CH3 C O O H N H CH3 H CH3 C O N H CH3 + H O H Acetic Acid Methyl Amine Methylammonium Acetate N-Methylacetamide Heat A Carboxylic Acid An Amine An Amine Salt An Amide The high heat needed to form amides from carboxylic acids and amines causes racemization (loss of handedness) decomposition or unwanted side reactions in compounds with reactive side groups (like alcohols). Thus, milder alternatives for forming amides are required using carboxylic acid derivatives like esters or anhydrides. CH3 C O O C O CH3 + H N H CH3 CH3 C O N H CH3 + Acetic AcidMethyl Amine N-Methylacetamide An Amine An Amide Acetic Anhydride H O C O CH3 Amide Hydrolysis: Amides, like proteins, can easily be hydrolyzed. Amides can be broken down into carboxylic acids and ammonia (or amines). Hydrolysis takes place in either an acid or a base. Acid hydrolysis produces the carboxylic acid and ammonium salt. + H N H H Cl H CH3 C O N H H + Acetic AcidAcetamide H O H HCl CH3 C O OH Ammonium Chloride In a base, the hydrolysis reaction produces the salt of the carboxylic acid and ammonia (or the amine). The odor of ammonia and the reaction of ammonia with litmus paper are used to detect the hydrolysis reaction of unsubstituted amines. + H N H HCH3 C O N H H + Sodium AcetateAcetamide (an unsubstituted amine) NaOH CH3 C O O Na Ammonia (a gas) H O H CH105 Lab 19: Amines & Amides 250 Urea: Urea is a waste product of protein metabolism; urea is removed from the blood by the kidneys and eliminated in the urine. Urea is used as a fertilizer and to make plastic resins. Proteins: The reactions of amines and amides resemble reactions of proteins in body chemistry. In later studies we shall see that proteins are complex amides that are hydrolyzed in the process of digestion to amino acids--compounds containing both an amino (-NH2) group and a carboxyl (- COOH) group. The amino acids are absorbed into the bloodstream and transported to the cells, where they are reformed into proteins needed by the body. Proteins in Food (Amides) H2O Amino Acids (Amines and acids) Body Proteins (Amides) Hydrolysis (Digestion) Amide synthesis (Reactions in cells) CH105 Lab 19: Amines & Amides 251 PROCEDURES: ACTIONS: I. ISOLATION OF CAFFEINE: 1. Pour 200 mL of a caffeinated beverage1 into a 500-mL Erlenmeyer flask. 2. Add sodium carbonate2 until the solution is basic.3 3. Pour the basic beverage solution into a 500 mL separatory funnel and add 25 mL of methylene chloride,4 (CH2Cl2). Shake (burping often) for 3 to 5 minutes to mix. 4. Drain the bottom layer (CH2Cl2 layer) into a beaker. 5. Under a fume hood evaporate the solution to dryness by placing the beaker over a hot water bath (or steam bath). The white residue that remains is primarily caffeine.5 Proceed to other sections of the lab while you are waiting for evaporation then return to deal with the caffeine later. 6. Describe the odor and appearance of the crude caffeine.6 7. Compare the identity and purity of the isolated caffeine to that of known caffeine by thin layer chromatography on a fluorescent silica plate as follows:7 A. Dissolve a little crude caffeine by adding a couple drops of dichloromethane (CH2Cl2) to your beaker. Swirl to mix. B. Prepare a 4 cm x 9 cm fluorescent silica TLC plate as shown using a pencil to mark 3 origin locations (A, B, & C). 7 C. On origins A and B place several spots of your crude caffeine allowing each spot to dry before applying another. 8 D. On origins B and C place several spots of a known sample of caffeine allowing each spot to dry before applying another.9 E. Place the plate into a 400 mL beaker containing 15 mLs of developing solvent (75% ethyl acetate and 25% hexane). 10 NOTES: 1Caffeinated beverages could include sodas (such as colas, Jolt or Mountain Dew), coffee, or tea. 2The sodium carbonate is added to remove any benzoic acid that may be present. 3Monitor with pH paper. 4The common name of dichloromethane (CH2Cl2) is methylene chloride. 5The caffeine may be purified by sublimation--the process of changing from a solid directly to the gaseous state. The vapor produced will solidify on a cold surface. To sublime, place an evaporating dish filled with cold water on the beaker and heat the beaker on a steam bath. The crystals that form on the underside of the dish are purified caffeine. 6Optional: Weigh the flask and determine the weight of crude caffeine. Calculate the percent of caffeine from tea. The percent (m/v %) of caffeine in your sample can be calculated since you know the grams of caffeine produced and you know the volume of beverage with which you began. 7Handle the plates at the edge only to avoid transferring substances from your fingers and to avoid rubbing the silica from the plate. Any markings or labels must be drawn with pencil rather than pen to avoid separation of any ink pigments. Markings must be made lightly to avoid scraping the silica from the plate. 8When the sample spot dries you can apply again. The spot must be kept small and not allowed to flow into larger spots. Your caffeine will show dark under UV light which can help you judge if enough compound has been applied to the plate. 9You are placing spots of your isolated caffeine and spots of known caffeine on the same origin mark B in what is called a “cospot”. If the two samples you have are different then they will separate by chromatography into two spots. However, if they are the same then only one sample spot will result. 10Keep the solvent level below the origin so that the solvent does not wash the samples away. A B C CH105 Lab 19: Amines & Amides 254 CH105 Lab 19: Amines & Amides 255 LAB 19: AMINES & AMIDES: NAME_____________ PRE LAB EXERCISES: DATE______________ Classify each of the following amines as A. primary, B. secondary, C. tertiary, D. quaternary. ___1. CH3CH2 N CH2CH3 CH3 ___2. N CH3 H CH3 ___3. H2N ___4. NH2 ___5. What substances turn red litmus paper to a blue color? A. Acids B. Bases C. Alcohols D. Esters ___6. If a substituted amide is hydrolyzed in base the products will be ______ A. a carboxylic acid and ammonia B. a carboxylic acid and a 1o or 2 o amine C. a carboxylic acid salt and ammonia D. a carboxylic acid salt and a 3 o amine E. a carboxylic acid salt and a 1o or 2 o amine F. a carboxylic acid and an amine salt ___7. If an amide is hydrolysed in the presence of base and ammonia gas is produced what might we conclude about the structure of the amide? A. The amide was unsubstituted B. The amide was monosubstituted C. The amide was disubstituted D. The amide must have been urea. ___8. What precautions should be taken when working with aniline? A. pregnant women should not check the odor. C. wash your hands after use. B. avoid skin contact as it is a deadly poison. D. all of these. ___9. The name of CH2Cl2 is A. Dichloromethane B. Methylene Chloride C. All of these CH105 Lab 19: Amines & Amides 256 CH105 Lab 19: Amines & Amides 259 ___3. My results show that the odor of amines is generally ________ .: (list all that apply) A. weak to none B. strong to pungent C. sweet D. variable E. other ____ ___4. My results show that the odor of amine salts is generally ________ .: (list all that apply) A. weak to none B. strong to pungent C. sweet D. variable E. other ____. Explain Why: Error Analysis and/or explanation of results: Are your experimental results as expected or are there discrepancies? Explain. III. Properties of Quinine: Acidity? Acid (A) or Base (B) Observations under Black light Tonic Water After addition of NaOH After addition of H2SO4 ___5. What is the fluorescent compound present in tonic water? A. Quinine B. The acid salt of Quinine C. NaOH D. H2SO4 E. Other (state) __________________________ Show the equation for the reaction of quinine hydrogen sulfate with sodium hydroxide: Use structures (not formulas) for organic compounds Error Analysis and/or explanation of results: Are your experimental results as expected or are there discrepancies? Explain. CH105 Lab 19: Amines & Amides 260 IV. Hydrolysis of Urea: Observations: Show the equation for hydrolysis of Urea with base. Use structures (not formulas) for organic compounds. Name the products formed: ___6. According to my results, the red litmus paper held over the basic hydrolysis of urea ____ A. turned blue B. turned a deeper red C. stayed the same ___7. The litmus reacted as it did because of the presence of ________________________ A. Ammonia gas B. methylamine C. sodium hydroxide D. Urea Error Analysis and/or explanation of results: Are your experimental results as expected or are there discrepancies? Explain. RELATED EXERCISES: 1.___ What are the products of acid catalyzed hydrolysis of a substituted amide? A. a carboxylic acid and an ammonium salt B. a carboxylic acid salt and a primary or secondary amine C. a carboxylic acid and a primary or secondary amine salt D. a carboxylic acid and a tertiary amine salt E. a carboxylic acid salt and tertiary amine 2.___ Which of the following amides would produce ammonia upon hydrolysis in base? A. N-methylacetamide B. benzamide C. N,N-diethylaniline CH105 Lab 19: Amines & Amides 261 3. Draw the equation for the reaction of atropine with sulfuric acid: N CH3 O C O OH H2SO4 Atropine 4. The artificial sweetener aspartame (NutraSweet) is a dipeptide, a very short protein molecule. The sweetness of aspartame was discovered accidentally in 1965 when a careless chemist licked his dirty fingers. He was fortunate that the compound was not toxic; his company was fortunate that he was curious to discover why his fingers were so sweet. Identify the functional groups in the aspartame molecule. A. alcohol B. amine C. carboxylic acid D. amide E. ester F. ether G. aldehyde H. ketone H N H C H C O N H C H C O O C H H HCH2CH2 C O OH NaOH H2O Aspartame (Nutrasweet) 5. Complete the equation for the basic hydrolysis of aspartame (Nutrasweet)