COMEDK · Chemistry · 27. Aldehydes and Ketones

Choose the incorrect statement.

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

Verified Solution

Answer & Solution

Correct Answer

(B) The increasing order of boiling points of 5 compounds having comparable molar masses is as follows:
Methoxyethane \(<\) Propanone \(<\) Propanal \(<\) Propan-1-ol

Step-by-step Solution

Detailed explanation

Statement (2) is incorrect because ketones have higher boiling points than isomeric aldehydes due to greater dipole-dipole interactions from two electron-donating alkyl groups. Propanone (b.p. \(\approx 56°C\)) boils higher than Propanal (b.p. \(\approx 49°C\)). The correct…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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