Question

Rank the following compounds from highest boiling to lowest boiling. To rank items as equivalent, overlap them. 

Rank the following compounds from highest boiling to lowest boiling. To rank items as equivalent, overlap them. 

Answer 1

The order of given bromoalkanes as per their boiling points is bromohexane > bromopentane > bromobutane from highest to lowest. Among these bromoalkanes, boiling points increase with increase in alkyl chain length. With increase in alkyl chain length, molecular size increases which results in increase in London dispersion forces that resulted in higher boiling points.

Among pentane, chlorobutane, pentanol and butanol the order from higest to lowest boiling points is :

pentanol> butanol > chlorobutane > pentane

In comparison to unsubstituted alkane (pentane), halogen and hydroxy substituted compounds (chlorobutane, butanol) have higher boiling points due to increase in molecular size leading to increase in London dispersion forces. In addition, dipole -dipole interactions also exist between chlorine atom of one chloroalkane and carbon atom of another chloroalkane molecule.

The alcohols (butanol and pentanol) have higher boiling point in comparison to alkanes and halo alkanes mainly due to their ability to form intermolecular hydrogen bonding.

Answer 2

1.  bromohexane > bromopentane > bromobutane

2. pentanol> butanol > chlorobutane > pentane