CBSE Class 12 · 2005 · Delhi; also Foreign · Compounds Containing NitrogenVery Short Answer

Why do primary amines have higher boiling points than tertiary amines?

Answer: 1° amines have two N–H bonds → intermolecular hydrogen bonding; 3° amines have none.

Solution

R–NH

_{2}

molecules associate through N–H···N hydrogen bonds; a tertiary amine R

_{3}

N has no N–H and relies on weak dipole forces alone — so, for comparable mass, the primary amine boils higher.

CBSE Class 12 Board · 2005 · Delhi; also Foreign · Subjective