Question

1. Addition of HBr to propene yields 2- Bromopropane, while in the presence of Benzoyl peroxide. The same reaction yields 1-Bromopropane. Give reason. Justify your answer. 

2. Three compounds are given. Benzene, m dinitrobenzene and toluene. Identify the compound which will undergo nitration most easily and why?

Answer 1

1. When propene is allowed to react with HBr in the presence of “peroxide” 2- Bromopropane is obtained as the minor product. (Peroxide effect or Kharach effect or Anti-Markowniko’s role of addition) Peroxide effect is applicable only in the case of HBr.

2. Toluene. This is because the -CH₃ group, being an activating group activates the benzene ring towards electrophilic substitution in toluene.