What are petrochemicals? Discuss their importance. 

Arrange benzene, n-hexane and ethyne in decreasing order of acidic behaviour. Also give a reason for this behaviour.

Identify the compound 'D' in the following series of reactions.

Benzene can be conveniently converted into n-propyl benzene by

• Friedel-Craft alkylation with n-propyl chloride

• Friedel-Craft acylation with propionyl chloride followed by Wolff-Kishner reduction

• Friedel-Craft acylation with propionyl chloride followed by catalytic hydrogenation

• Friedel-Craft acylation with propionyl chloride followed by reduction with LiAlH₄

At 300 K and 1 atm, 15 mL of a gaseous hydrocarbon requires 375 mL air containing 20% O2 by volume for complete combustion. After combustion the gases occupy 330 mL. Assuming that the water formed is in liquid form and the volumes were measured at the same temperature and pressure, the formula of the hydrocarbon is:

• C₃H₈

• C₄H₈

• C₄H₁₂

• C₄H₁₂