n-butylamind(I), diethylamine (II) and N,N-dimethylethylamine (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. `II lt III lt I`
D. `III lt Ilt II`

Answer

A

Explanation

Intermolecuilar `H-` bonding is more inprimary 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 available for H-bonding. Therefore, the order of boiling points of the given amines is as follows:
`underset(b.p.350.8K)(._(n)C_(4)H_(g)NH_(2))gtunderset(b.p.329.3K)((C_(2)H_(5))_(2)NH)gtunderset(b.p.310.5K)(C_(2)H_(5)N(CH_(3))_(2)`