Free Nomenclature, Structure and Preparation MCQs with Answers

1. Ethanoic acid can be prepared by the oxidation of

• A. ethanol under reflux with acidified potassium dichromate
• B. ethene with bromine water
• C. propanone with Tollens reagent
• D. ethane with oxygen at room temperature

Explanation: Refluxing keeps the intermediate ethanal in the flask so that oxidation continues to the acid, whereas distilling the product off as it forms would stop the reaction at the aldehyde. The dichromate turns from orange to green as it is reduced. Vinegar is made industrially by the bacterial oxidation of ethanol instead.

2. Hydrolysis of a nitrile such as ethanenitrile with dilute acid gives

• A. an amine
• B. an aldehyde
• C. an alcohol
• D. a carboxylic acid with the same number of carbon atoms as the nitrile

Explanation: The carbon of the nitrile group becomes the carbon of the carboxyl group, so hydrolysing ethanenitrile gives ethanoic acid and ammonia is released as its salt. Since the nitrile itself was made by adding cyanide to an alkyl halide with one fewer carbon, the two steps together lengthen the chain by one. Reduction rather than hydrolysis of a nitrile gives a primary amine.

3. The IUPAC name of CH3CH2COOH is

• A. ethanoic acid
• B. butanoic acid
• C. propanoic acid
• D. propan-1-ol

Explanation: The molecule has three carbon atoms in total, and the carboxyl carbon is always counted as part of the chain and numbered one, so the name is propanoic acid. Forgetting to count the carboxyl carbon gives ethanoic acid, which is the standard error. The parent acid name is formed by replacing the final e of the alkane with the ending oic acid.