N-butylamine (I), diethylamine (II) and N,N-dimethyl ethylamine(III) have the same molar mass. The increasing order of their boiling point is:

Options

A. `III lt II lt I`
B. `I lt II lt III`
C. `III lt I lt II`
D. `II lt I lt III`

Answer

A

Explanation

Intermolecular H-bonding is more in primary amines than in secondary amines as there are two H-atoms available for H-bonding. Tertiary amines do not have intermolecular H-bonding due to absence of H-atoms. Therefore, the order of boiling points of the given amines is as follows `{:(nC_4H_9NH_2, gt , (C_2H_5)_2NH, gt , C_2H_5N(CH_3)_2),("bp=350.8 K", , "bp=329.3 K",,"bp=310.5 K"):}`