Question

Choose the incorrect statement.

• A. The increasing order of boiling points of 5 compounds having comparable molar masses is as follows: Methoxyethane \( < \) Propanone \( < \) Propanal \( < \) Propan-1-ol
• B. During nucleophilic addition of HCN to RCHO, the hybridisation changes from sp\(^2\) to sp\(^3\) and a tetrahedral intermediate is formed.
• C. Acetone undergoes Wolff Kishner reaction to yield Propane.
• D. The order of reactivity towards nucleophilic attack is Methanal \( > \) Di-tert.butyl ketone \( > \) Benzaldehyde \( > \) Acetophenone.

Hint:

Boiling points increase with the strength of intermolecular forces. Alcohols tend to have higher boiling points than aldehydes and ethers due to hydrogen bonding.

Answer 1

The Correct Option is A

Step 1: Analyze option (A).
The increasing order of boiling points is based on intermolecular forces such as hydrogen bonding and polarity. Among the compounds mentioned, Methoxyethane (CH\(_3\)OCH\(_3\)) is an ether with weak Van der Waals forces, so it should have a lower boiling point than the aldehyde and alcohol. Therefore, this statement is incorrect.

Step 2: Analyze option (B).
In the nucleophilic addition of HCN to an aldehyde (RCHO), the carbonyl carbon (sp\(^2\) hybridised) accepts the nucleophile (HCN), leading to a tetrahedral intermediate. This is correct.

Step 3: Analyze option (C).
The Wolff-Kishner reduction converts carbonyl compounds into alkanes, and it works well with compounds like ketones and aldehydes. Acetone, being a ketone, does undergo this reaction to yield propane. This statement is correct.

Step 4: Analyze option (D).
The order of reactivity towards nucleophilic attack is correct, as aldehydes like Methanal are more reactive due to the electron-withdrawing nature of the carbonyl group. Di-tert.butyl ketone is less reactive due to steric hindrance. This statement is correct.

Step 5: Conclusion.
Thus, the incorrect statement is option (A).