Question

Which of the following is not a correct statement for primary aliphatic amines?

• A. Primary amines can be prepared by the Gabriel phthalimide synthesis.
• B. Primary amines are less basic than the secondary amines.
• C. The intermolecular association in primary amines is less than the intermolecular association in secondary amines.
• D. Primary amines on treating with nitrous acid solution form corresponding alcohols except methyl amine.

Hint:

The strength of intermolecular hydrogen bonding depends on the number of H-atoms available on the electronegative N atom. \(1^\circ\) Amine (2 H) > \(2^\circ\) Amine (1 H) > \(3^\circ\) Amine (0 H).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
This question tests general properties and preparation methods of primary aliphatic amines.
Step 2: Detailed Explanation:
(A) Statement A is correct. Gabriel phthalimide synthesis is a standard method used to prepare pure primary aliphatic amines.
(B) Statement B is correct. In aqueous solution, secondary amines are generally more basic than primary amines due to the combined effect of the \(+I\) effect of alkyl groups and solvation effects.
(C) Statement C is incorrect. Primary amines (\(RNH_2\)) have two hydrogen atoms bonded to nitrogen, while secondary amines (\(R_2NH\)) have only one. Therefore, primary amines can form more extensive hydrogen bonds, leading to stronger intermolecular association and higher boiling points compared to secondary amines of comparable molecular mass.
(D) Statement D is correct. Primary aliphatic amines react with nitrous acid to yield alcohols and nitrogen gas. However, methylamine (\(CH_3NH_2\)) yields a mixture of products including methanol, dimethyl ether, and methyl nitrite.
Step 3: Final Answer:
The incorrect statement is (C).