Chapter 25, Problem 25.49P

Interpretation Introduction

(a)

Interpretation:

The major product of the reaction shown here is to be predicted and the complete, detailed mechanism is to be provided.

Concept introduction:

This is an example of a radical addition mechanism. A free radical chain reaction involves free radicals in a cyclic sequence of steps, called propagation steps, which are responsible for converting overall reactants into overall products. Throughout the sequence of propagation steps, also called the propagation cycle, there is no net consumption of free radicals. The overall reaction is obtained by summing just the propagation steps. An initiation step is responsible for producing the free radical that enters the propagation cycle.

Interpretation Introduction

(b)

Interpretation:

The major product of the reaction shown here is to be predicted and the complete, detailed mechanism is to be provided.

Concept introduction:

This is not a radical mechanism since no initiator (heat, light, or peroxides) is present. A hydrogen halide adds across the double bond of an alkene in a Markovnikov fashion under normal conditions. Thus, $\text{HBr}$, a strong Bronsted acid, undergoes electrophilic addition, across the $\text{C=C}$ bond. ${\text{H}}^{\text{+}}$ adds to the less alkyl-substituted $\text{C}$ atom, whereas ${\text{Br}}^{\text{-}}$ adds to the more alkyl-substituted $\text{C}$ atom.