Answer
this is due to the presence of one additional hydrogen bond in the structure of dimethyl amine between N and H in (CH3)2NH which is absent in trimethylamine (CH3)3N.
Work Step by Step
dimethyl amine has higher boiling point than trimethyl amine even though it has lower molecular weight. this is due to the presence of one additional hydrogen bond in the structure of dimethyl amine between N and H in (CH3)2NH which is absent in trimethylamine (CH3)3N.