Chemistry 2050 Introduction to Organic Chemistry Fall Semester 2011 Dr. Rainer Glaser Examination #4 Make-Up Carbonyl Compounds and Amines. Wednesday, November 30, 2011, 10 10:50 am Name: Answer Key Question 1. Aldehydes and Ketones 20 Question 2. Carboxylic Acids and Anhydrides 20 Question 3. Carboxylic Acid Esters 20 Question 4. Carboxylic Acid Halides 20 Question 5. Amines and Diazonium Ions 20 Total 100 1
Question 1. Aldehydes and Ketones. (20 points) (a) Provide abbreviated structural formula of the final product of the hydration of 1-butyne using proton and Hg 2+ catalysis. Name the product (any acceptable name receices full credit). (4 points) (b) Provide abbreviated structural formula of the final product of the reaction of 2-butanone with (1) methylmagnesium bromide and (2) dilute aqueous acid. The product (contains, does not contain) a chiral center and it is formed as (one achiral product, one pure enantiomer, a non-racemic mixture, a racemate). (6 points) (c) Draw the structural formula of the product of the reaction of acetophenone (H 5 C 6 CO CH 3 ) with aniline, H 5 C 6 NH 2. The product is a IMINE (name of this type of N- derivative of carbonyl compounds). (4 points) (d) The compound shown can be prepared in two steps beginning with acetaldehyde. The first reaction is a base-catalyzed aldol reaction and the second reaction is the elimination of WATER. Provide the abbreviated structural formula of the aldol below. (6 points) Acetaldehyde Aldol 2
Question 2. Carboxylic Acids and Anhydrides. (20 points) (a) The boiling points of carboxylic acids are rather high because they form strongly bonded dimeric aggregates. Draw the dimer formed by propanoic acid, H3C CH2 COOH, below and select the electrostatic potential surface plot of this dimer. (6 points) (b) Syntheses of carboxylic acids. Provide substrate, reagent or product as requested. (10 points) Product formed by oxidation of Product formed by oxidation of ethylbenzene, Toluene, C6H5 CH3 with hot KMnO4: C6H5 CH2 CH3 with hot KMnO4: C6H5 COOH C6H5 COOH Reagent that reacts with phenylmagnesium bromide, H5C6MgBr to form benzoic acid, H5C6 COOH after workup with dilute acid: Product of the acid-catalyzed hydrolysis of benzonitrile, H5C6 C N: C6H5 COOH O=C=O (c) Maleic acid is the trivial name of cisbutendioic acid. Heating maleic acid leads to water elimination and the formation of an intramolecular acid anhydride. Draw the structure of the intramolecular acid anhydride formed in the box to the right. (4 points) 3
Question 3. Carboxylic Acid Esters. (20 points) (a) Ethyl acetate H 3 C CO O C 2 H 5 is part of nail polish remover, model paint, and model airplane glue. Ethyl acetate can be made by Fischer esterification of the carboxylic acid (formic acid, acetic acid, benzoic acid) and the alcohol (methanol, ethanol, phenol). Fischer esterification means that the ester formation is catalyzed by a strong mineral acid. (4 points) (b) Consider the mechanism of the formation of ethyl acetate H 3 C CO O C 2 H 5 by Fischer esterification. Draw the structural formulas of the species indicated. Draw all lone pairs, provide all formal charges. You may abbreviate the methyl group as H 3 C or as Me and the ethyl group as H 5 C 2 or as Et. (12 points) 1: Protonated carboxylic acid, i.e., the actual substrate for alcohol addition 2: Product formed by addition of alcohol to the protonated carboxylic acid 3: Neutral gem tri-functional intermediate 4: Protonated gem tri-functional intermediate that will lead to water elimination (c) Consider the reaction of ethyl acetate with methylamine. Provide the structural formulas of all the products formed in the reaction. (4 points) 4
Question 4. Carboxylic Acid Halides. (20 points) (a) Consider the preparation of benzoyl chloride from benzoic acid using phosphorus pentachloride. Draw structural formulas of the substrate, of the reagent, of the organic product (the benzoyl chloride), and also of the inorganic products. (8 points) (b) Consider the formation of acetamide by reaction of acetyl chloride (H 3 C CO Cl) with ammonia (NH 3 ). Explain why two molecules of ammonia are required for every molecule of acetyl chloride. Your explanation should include the reaction equation for the acetamide formation. (4 points) (c) The synthesis is outlined of 4-methylacetophenone in two reaction steps. Complete this scheme by providing the three chemicals. The inorganic reagent used in the first reaction is a sulfur compound which is called thionylchloride (provide name). The second step is a Friedel-Crafts acylation. (8 points) 5
Question 5. Amines and Diazonium Ions. (20 points) (a) Consider the reaction of triethylamine, N(C 2 H 5 ) 3 with benzyl iodide, H 5 C 6 CH 2 I. Draw the structure of the product and provide its name. (6 points) N-benzyl-N,N,N-triethylammonium iodide (b) Devise a synthesis of acetanilide by reaction of aniline (aminobenzene) with acetic acid anhydride. Draw the structures of aniline, of acetic acid anhydride, of the product acetanilide, and of the other product formed from the anhydride. (8 points) (c) Complete this scheme by providing the structure of the intermediate (center box) and the two reagents (boxes over arrows). (6 points) 6