Question

(a) Arrange the following compounds in increasing order of their boiling point: \[ \text{(CH}_3\text{)}_2\text{NH, CH}_3\text{CH}_2\text{NH}_2, \text{CH}_3\text{CH}_2\text{OH} \] 

Hint:

Boiling points increase with the strength of intermolecular forces. Alcohols have stronger hydrogen bonding than amines, which leads to higher boiling points.

Answer 1

To arrange the compounds in increasing order of their boiling points, we need to consider the type and strength of intermolecular forces. The compounds are: 1. Dimethylamine \((\text{CH}_3)_2\text{NH}\): This compound is a simple amine with weak hydrogen bonding. It will have a lower boiling point compared to alcohols but higher than alkyl amines due to the possibility of dipole-dipole interactions. 2. Ethylamine \(\text{CH}_3\text{CH}_2\text{NH}_2\): Similar to dimethylamine, but it has a slightly higher boiling point because the ethyl group is larger than the methyl group, which introduces slightly stronger van der Waals forces. 3. Ethanol \(\text{CH}_3\text{CH}_2\text{OH}\): Ethanol has hydrogen bonding due to the presence of the hydroxyl group, which significantly increases its boiling point compared to the amines. Thus, the order of boiling points from lowest to highest is: \[ (\text{CH}_3)_2\text{NH}<\text{CH}_3\text{CH}_2\text{NH}_2<\text{CH}_3\text{CH}_2\text{OH} \]