Question

In alkane compounds with same number of carbon atoms, straight chain isomers have higher boiling point as compared to branched chain isomers-justify statement.

Answer 1

• The boiling point of continuous chain alkanes increases with increase in the length of carbon chain roughly about 30°C for every added carbon atom to the chain. 
• Alkanes are non-polar compounds and having weak Vander Wal’s force which depends upon molecular surface area and hence increases with increase in molecular size. 
• The boiling point decreases with increase in branching on the molecule i.e. as it becomes compact and the area of the contract decreases. Hence in alkanes with same number of carbon atoms, straight chain isomers have higher boiling point as compared to branched chain isomers.