JEE Chemistry 2023 Question with Solution

Given: Assertion $A$ states that acetal/ketal is stable in basic medium. Reason $R$ states that high leaving tendency of alkoxide ion gives this stability.

Find: Which option correctly describes the truth of $A$ and $R$.

Acetals and ketals are essentially ether-like compounds, so they are stable in basic medium and are generally cleaved in acidic medium. Therefore, Assertion $A$ is true.

For the reason, alkoxide ion $\text{RO}^-$ is not a good leaving group. Therefore, the statement that high leaving tendency of alkoxide ion gives stability is incorrect. Hence Reason $R$ is false.

Therefore, the correct option is C.

Given:

• Acetal/ketal stability in basic medium
• Claim about leaving tendency of alkoxide ion $\text{RO}^-$

Find: The correct relationship between the assertion and reason.

1. Acetals and ketals do not undergo hydrolysis in basic medium easily.
2. Their cleavage occurs in acidic medium because protonation helps generate a better leaving group.
3. In basic medium, alkoxide ion $\text{RO}^-$ would have to leave directly.
4. Since $\text{RO}^-$ is a poor leaving group, this does not support the reason given.

So, the assertion is correct, but the reason is false.

Hence, the correct option is C.