Question

Which of the following dicarboxylic acids does not yield anhydride on heating?

• A. Glutaric acid
• B. Maleic acid
• C. Dimethyl succinic acid
• D. Dimethyl malonic acid

Hint:

Substituents like methyl groups on dicarboxylic acids can hinder the formation of anhydrides due to steric hindrance.

Answer 1

The Correct Option is D

Step 1: Anhydride Formation.
When heating dicarboxylic acids, they typically undergo dehydration to form anhydrides. However, the presence of bulky substituents on the carboxyl groups can hinder this process.

Step 2: Analysis of Options.
- (1) Glutaric acid: Glutaric acid can form an anhydride upon heating.
- (2) Maleic acid: Maleic acid can also undergo dehydration to form an anhydride.
- (3) Dimethyl succinic acid: Dimethyl succinic acid, with methyl groups on the carboxyl groups, still readily forms anhydride.
- (4) Dimethyl malonic acid: The bulky methyl groups on the carboxyl groups prevent the formation of an anhydride. Therefore, this acid does not readily form anhydride on heating.

Step 3: Conclusion.
Thus, the correct answer is (4) Dimethyl malonic acid.

Final Answer: \[ \boxed{\text{(4) Dimethyl malonic acid}} \]