Chapter 25, Problem 25.43P

Interpretation Introduction

(a)

Interpretation:

The complete mechanism leading to the two major products is to be drawn and whether the product mixture will be optically active is to be determined.

Concept introduction:

When an alkane such as $\text{cyclohexane}$ is treated with a molecular halogen such as ${\text{Cl}}_{\text{2}}$, no reaction occurs. However, if the same mixture is irradiated with UV light, then halogenation takes place, producing $\text{chlorocyclohexane}$ and $\text{HCl}$. The mechanism involves free radical intermediates, so the reaction is more specifically called a radical halogenation. Radical halogenation is a substitution reaction in which a hydrogen atom from an alkane is replaced by a halogen atom from a molecular halogen, ${\text{X}}_{\text{2}}$, producing a hydrogen halide as a by-product. An initiation step is responsible for producing the free radical that enters the propagation cycle. 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.

Interpretation Introduction

(b)

Interpretation:

The complete mechanism leading to the two major products is to be drawn and whether the product mixture will be optically active is to be determined.

Concept introduction:

When an alkane such as $\text{cyclohexane}$ is treated with a molecular halogen such as ${\text{Cl}}_{\text{2}}$, no reaction occurs. However, if the same mixture is irradiated with UV light, then halogenation takes place, producing $\text{chlorocyclohexane}$ and $\text{HCl}$. The mechanism involves free radical intermediates, so the reaction is more specifically called a radical halogenation. Radical halogenation is a substitution reaction in which a hydrogen atom from an alkane is replaced by a halogen atom from a molecular halogen, ${\text{X}}_{\text{2}}$, producing a hydrogen halide as a by-product. An initiation step is responsible for producing the free radical that enters the propagation cycle. 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.