Organic Chemistry Multiple Choice Questions on “Esters”.
1. Which of the following compounds is an ester?
a) 
b) 
c) 
d) 
Answer: c
Clarification: Esters are characterized by their possession of a modified carboxyl group, in which the H of the -OH group is replaced by an alkyl group, to form the general functional group -COOR.
2. Which of the following is used as catalyst for the esterification of carboxylic acid and alcohol?
a) Nitrous acid
b) Sulphuric acid
c) Sulphurous acid
d) Nitric acid
Answer: b
Clarification: The classic synthesis is the Fischer esterification, which involves treating a carboxylic acid with an alcohol in the presence of a dehydrating agent:
RCO2H + R′OH ⇌ RCO2R′ + H2O
The equilibrium constant for such reactions is about 5 for typical esters, e.g., ethyl acetate. The reaction is slow in the absence of a catalyst. Sulfuric acid is a typical catalyst for this reaction.
3. What will be the product for the given reaction?
CH3OH + CO →?
a) Ethyl formate
b) Methyl formate
c) Ethyl acetate
d) Methyl acetate
Answer: b
Clarification: The carbonylation of methanol yields methyl formate, which is the main commercial source of formic acid.
CH3OH + CO → CH3O2CH
4. Hydrolysis of ester leads to the formation of which of the following products in basic medium?
a) Ether and alcohol
b) Alcohol and sodium carboxylate
c) Aldehyde and alcohol
d) Sodium carboxylate
Answer: b
Clarification: Under basic conditions, hydroxide acts as a nucleophile, while an alkoxide is the leaving group.
5. What will be the product for the given reaction?
C2H4 + CH3CO2H + 1⁄2 O2 →?
a) Ethyl formate
b) Vinyl formate
c) Ethyl acetate
d) Methyl acetate
Answer: b
Clarification: In the presence of palladium-based catalysts, ethylene, acetic acid, and oxygen react to give vinyl acetate:
C2H4 + CH3CO2H + 1⁄2 O2 → C2H3O2CCH3 + H2O
6. What is the characteristic smell for ester?
a) Fruity like smell
b) Fish like smell
c) Rotten egg smell
d) Alcoholic smell
Answer: a
Clarification: Many esters have distinctive fruit-like odors, and many occur naturally in the essential oils of plants. This has also led to their commonplace use in artificial flavorings and fragrances when those odors aim to be mimicked.
7. Salts of carboxylate anions can be alkylating agent with alkyl halides to give esters. In the case that an alkyl chloride is used, an iodide salt can catalyze the reaction. What is the name reaction for the given reaction?
a) Favorskii rearrangement
b) Baeyer–Villiger oxidation
c) Pinner reaction
d) Finkelstein reaction
Answer: d
Clarification: Salts of carboxylate anions can be alkylating agent with alkyl halides to give esters. In the case that an alkyl chloride is used, an iodide salt can catalyze the reaction this reaction is known as Finkelstien reaction.
8. What will be the product of given reaction?
a) Ether and alcohol
b) Alcohol and sodium carboxylate
c) Aldehyde and alcohol
d) Carboxylic acid and alkene
Answer: d
Clarification: Ester pyrolysis in is a vacuum pyrolysis reaction converting esters containing a β-hydrogen atom into the corresponding carboxylic acid and the alkene.