MHT CET · Chemistry · Alcohols Phenols and Ethers

The correct order of boiling point for primary \(\left(1^{\circ}\right)\), secondary \(\left(2^{\circ}\right)\) and tertiary \(\left(3^{\circ}\right)\) alcohols is

A \(1^{\circ}>2^{\circ}>3^{\circ}\)
B \(3^{\circ}>2^{\circ}>1^{\circ}\)
C \(2^{\circ}>1^{\circ}>3^{\circ}\)
D \(2^{\circ}>3^{\circ}>1^{\circ}\)

Verified Solution

Answer & Solution

Correct Answer

(A) \(1^{\circ}>2^{\circ}>3^{\circ}\)

Step-by-step Solution

Detailed explanation

Alcohols with same molecular weight are expected to have almost same boiling point however two more factors other than molecular weight are important, they are namely H-bonding and surface area of molecule. Both these factors are least in \(3^{\circ}\) alcohols and maximum in \(1^{\circ}\) alcohols. Hence, \(3^{\circ}\) alcohols have least boiling point while \(1^{\circ}\) alcohols have maximum boiling point.

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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