Question

Arrange the following compounds in increasing order of their boiling points:
$\text{C}{\text{H}}_3\text{C}{\text{H}}_2\text{C}{\text{H}}_2\text{CHO,}\text{C}{\text{H}}_{\text{3}}\text{C}{\text{H}}_{\text{2}}\text{C}{\text{H}}_{\text{2}}\text{CH}{}_{\text{2}}\text{OH,}{\text{C}}_{\text{2}}{\text{H}}_{\text{5}}\text{O}{\text{C}}_{\text{2}}{\text{H}}_{\text{5}},\text{C}{\text{H}}_{\text{3}}\text{C}{\text{H}}_{\text{2}}\text{C}{\text{H}}_{\text{2}}\text{C}{\text{H}}_{\text{3}}$

Answer 1

Boiling point of organic compounds increases with increase in the bond polarity of the molecule. The greater the forces of attraction the higher the boiling point or the greater the polarity the higher the boiling point.

*Due to the formation of hydrogen bonding in alcohols they are more polar than aldehydes, ethers and hydrocarbons.

*Aldehydes have higher boiling points than ethers and hydrocarbons as they have weak intermolecular dipole-dipole forces.

*Ethers lack of any oxygen-hydrogen bond makes hydrogen bonding impossible and there is little intermolecular association, but have higher boiling point than hydrocarbons.

So, the correct order in increasing boiling point is -

$C{H}_{3}C{H}_{2}C{H}_{2}C{H}_3$ < $C_2{H}_{5}O{C}_2{H}_5$ < $C{H}_{3}C{H}_{2}C{H}_{2}CHO$ < $C{H}_{3}C{H}_{2}C{H}_{2}OH$