Chemistry 2030 “Introduction to Organic Chemistry” Fall Semester 2012 Dr. Rainer Glaser Examination #4
“Carbonyl Compounds and Amines.”
Thursday, November 15, 2012, 8:25 – 9:15 am
Name:
Question 1. Aldehydes and Ketones
20
Question 2. Carboxylic Acids and Anhydrides
20
Question 3. Carboxylic Acid Esters
20
Question 4. Carboxylic Acid Halides, Anhydrides and Amides
20
Question 5. Amines and Diazonium Ions
20
Total
— 1 — 100
Question 1. Aldehydes and Ketones. (20 points)
(a) Acetophenone (H5C6−CO−CH3) is an enolizable ketone. Draw the two important resonance forms
of the anion formed by deprotonation of acetophenone. Show all lone pairs and formal charges; use the
correct resonance arrow. Use curved arrows to show the electron flow that converts one resonance
forms into the other. (6 points)
(b) Draw the structural formula and provide the
name of one non-enolizable carbonyl (aldehyde
or ketone) of your choice. (4 points)
(c) The compound shown, but-2-enal, can be prepared in two steps beginning with acetaldehyde. The
first reaction is a base-catalyzed aldol reaction and the second reaction is the thermal elimination of
_________. Provide a structural formula of the aldol. In the structures of both the aldol and the but-2enal, circle the fragment that functioned as the enolate in the aldol reaction. (5 points)
Acetaldehyde Aldol
(d) Cinnamaldehyde (H5C6−CH=CH−CHO) can be prepared in a two-step sequence consisting of an
aldol reaction and thermal condensation. This synthesis involved a ________ aldol reaction between the
non-enolizable aldehyde _____________ and the enolizable aldehyde _______________. (5 points)
— 2 — Question 2. Carboxylic Acids and Anhydrides. (20 points)
(a) Carboxylic acids and carboxylic acid amides form strongly bonded dimeric aggregates either with
themselves (homodimer) or with each other (heterodimer). The electrostatic potential surface plots are
shown of the homodimer of propanoic acid, H3C−CH2−COOH, and of the heterodimer of
propanoic acid and its amide, H3C−CH2−CONH2. Decide which plot shows which dimer and draw
the complete structural formula of each dimer in the space above the plot. Indicate H-bonds as dashed
lines. (6 points)
(b) Syntheses of carboxylic acids. Provide substrate, reagent or product as requested. (12 points)
Product formed by oxidation of
Product formed by oxidation of p-xylene,
toluene, C6H5−CH3 with hot KMnO4:
H3C−C6H5−CH3 with hot KMnO4:
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 malononitrile, :N≡C−CH2−C≡N:
(c) Succinic acid is the trivial name of butanedioic
acid (note “butane”). Succinic anhydride is the
intramolecular anhydride of succinic acid. Draw
the structure of succinic anhydride in the box to
the right. (2 points)
— 3 — Question 3. Carboxylic Acid Esters. (20 points)
(a) Methyl formate H−CO−O−CH3 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. (2 points)
(b) Consider the mechanism of the formation of methyl formate H−CO−O−CH3 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 “H3C−” or as “Me−”. (12 points)
1: Protonated carboxylic acid, i.e., the actual
2: Product formed by addition of alcohol
substrate for alcohol addition
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 methyl formate with dimethylamine. Provide the structural formulas of
all the products formed in the reaction and provide an acceptable name for the amide. (6 points)
— 4 — Question 4. Carboxylic Acid Halides, Anhydrides and Amides. (20 points)
(a) Consider the preparation of acetyl chloride from acetic acid using phosphorus pentachloride.
Draw structural formulas of the substrate, of the reagent, of the organic product (the acetyl chloride),
and also of the inorganic products. (8 points)
(b) Consider the formation of N,N-dimethylacetamide, H3C−CO−N(CH3)2 by reaction of acetic
anhydride with dimethylamine. Two molecules of the amine are required for every molecule of acetic
anhydride used. Show reaction equations for the reaction A of the first amine with the anhydride and for
the reaction B of the second amine with the ____________ formed in the preceding reaction. (8 points)
(c) Draw the structures of the products of hydrolysis of N,N-dimethylacetamide, H3C−CO−N(CH3)2 in
the presence of NaOH. [Hint: Account for salt formation.] (4 points)
— 5 — Question 5. Amines and Diazonium Ions. (20 points)
(a) Consider the reaction of trimethylamine, N(CH3)3 with benzyl iodide, H5C6−CH2−I. Draw the
structure of the product and provide its name. (4 points)
(b) Devise a synthesis of N,N-diethyl-m-toluamide (the insect repellent OFFTM) by reaction of the
appropriate amine, _________________ (name of the amine), and m-toluyl chloride in the presence of
NaOH. Draw the structures of the amine, of the acid chloride, of the amide product, and of the
inorganic products. (10 points)
(c) Complete this scheme by providing the structure of the intermediate (center box) and the two
reagents (boxes over arrows). (6 points)
— 6 —