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Chemistry205Chemistry20500 “IntroductiontoOrganicChemistry” “IntroductiontoOrganicChemistry”

Fall Semester2011Fall Semester2011 Dr. RainerGlaser Dr. RainerGlaser

Examination #4

“Carbonyl Compounds and Amines.”

Wednesday, November 16, 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

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Question 1. Aldehydes and Ketones. (20 points) (a) Provide abbreviated structural formulas of the substrate and of the final product of the hydration of 1-octyne using proton and Hg2+ catalysis. Name the product (any acceptable name receices full credit). (4 points)

2-octanone

(b) Provide abbreviated structural formulas of the substrate and of the final product of the reaction of 3-hexanone 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 benzophenone (H5C6−CO−C6H5) with H5C6−NH−NH2. The product is a __PHENYLHYDRAZONE__ (name of this type of N-derivative of carbonyl compounds). (4 points)

(d) The mosquito repellent “6-12” (2-ethylhexane-1,3-diol, shown) can be prepared in two steps beginning with butanal. The first reaction is a base-catalyzed aldol reaction. Provide the abbreviated structural formula of the aldol below. The second reaction is a __HYDROGENATION_ and requires a catalyst such as ___Ni__. (6 points)

butanal aldol

“6-12”, 2-ethylhexane-1,3-diol

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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 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 toluene with hot KMnO4:

Ph−COOH

Product formed by oxidation of C6H5−CH2−CH2−CH3 with hot KMnO4:

Ph−COOH

Reagent that reacts with CH3MgBr to form H3C−COOH after workup with dilute acid:

O=C=O

Jones’ reagent to convert propanol to H3C−CH2−COOH:

CrO3 / H2SO4

(c) Phthalic acid, isophthalic acid and terephthalic acid are the three isomers of benzenedicarboxylic acid. Heating one of these isomers leads to water elimination and the formation of an intramolecular acid anhydride. Draw the structure of the intramolecular acid anhydride formed in the appropriate box. (4 points)

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Question 3. Carboxylic Acid Esters. (20 points) (a) The ester phenyl acetate H3C−CO−O−C6H5 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. If we wanted to make the 18O-labeled ester H3C−CO−18O−C6H5, then we would employ the 18O-labeled _________ (alcohol, carboxylic acid). (4 points) (b) Consider the formation of phenyl acetate H3C−CO−O−C6H5 using catalysis by a strong mineral acid. Abbreviate the phenyl ring as “H5C6−” or as “Ph−” and draw the complete structural formulas of the species indicated (draw all lone pairs, formal charges). The neutral gem tri-functional intermediate contains ___ (1, 2, or 3 hydroxyl group(s)) and ___ (1, 2, or 3 ether group(s)). (10 points)

Protonated carboxylic acid, i.e., the actual substrate for alcohol addition:

Product formed by addition of alcohol to the protonated carboxylic acid:

Neutral gem tri-functional intermediate:

Protonated gem tri-functional intermediate that will lead to water elimination:

(c) Consider the reaction of phenyl acetate with ammonia in ether solution. In the box on the left, provide the structural formulas of the substrate ester and of all the products formed in the reaction. In the box on the right, draw the neutral gem tri-functional intermediate of this reaction. (6 points)

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Question 4. Carboxylic Acid Halides. (20 points) (a) Consider the preparation of benzoyl chloride 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. (5 points)

(b) Consider the formation of acetamide by reaction of acetyl chloride with ammonia. 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. (5 points)

(c) Devise a synthesis of 4-methylacetophenone from toluene and acetic acid as starting materials. For each of two reaction steps, specify substrate, reagent(s), catalyst(s) and product formed. [Hint: Friedel-Crafts Acylation!] (10 points)

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Question 5. Amines and Diazonium Ions. (20 points) (a) Consider the reaction of triethylamine with benzyl iodide. Draw the structures of substrate and reagent and of the product. Provide the name of the reaction product. (8 points)

N-benzyl-N,N,N-triethylammonium iodide

(b) Devise a synthesis of acetanilide by reaction of aniline and a suitable carboxylic acid anhydride. Draw the structures of aniline, of the carboxylic acid anhydride, of the product acetanilide, and of the other product formed from the anhydride. (4 points)

(c) Devise a synthesis of fluorobenzene from aniline. For each of two reaction steps, specify substrate, reagent(s), catalyst(s) and product formed. [Hint: via benzenediazonium ion!] (8 points)