Chapter 11, Problem 11B.3E

Interpretation Introduction

Interpretation:

The products that are formed by the substitution reaction of ethane with chlorine has to be given and if the product exists as optical isomers has to be checked.

Concept Introduction:

Substitution reaction of alkanes:

Functionalization of alkanes is done by substitution reaction, where an atom (in alkanes, a hydrogen atom) in the original molecule replaces an atom or group of atoms.  Alkane substitution takes place by a radical chain mechanism.

Answer to Problem 11B.3E

Six products are obtained in the chlorination of ethane by free radical chain mechanism.

No, they do not exist as optical isomers.

Explanation of Solution

The reaction of chlorination of ethane takes place by free radical chain mechanism in the presence of ultraviolet radiation.  The chemical reaction is,

  $\begin{array}{l}{\text{C}}_{\text{2}}{\text{H}}_{\text{6(g)}}{\text{+Cl}}_{\text{2(g)}}\stackrel{\text{uv-light}}{\to }{\text{C}}_{\text{2}}{\text{H}}_{\text{5}}{\text{Cl}}_{\left(\text{g}\right)}{\text{+HCl}}_{\left(\text{g}\right)}\\ \text{Ethane}\text{Chloroethane}\end{array}$

Chloroethane is formed as one of the products.  The other products are,

  $\begin{array}{l}{\text{C}}_{\text{2}}{\text{H}}_{\text{5}}{\text{Cl}}_{\left(\text{g}\right)}{\text{+Cl}}_{\text{2(g)}}\stackrel{\text{uv-light}}{\to }{\text{C}}_{\text{2}}{\text{H}}_{\text{4}}{\text{Cl}}_{\text{2(g)}}{\text{+HCl}}_{\left(\text{g}\right)}\\ \text{Chloroethane}\text{Dichloroethane}\end{array}$

  $\begin{array}{l}{\text{C}}_{\text{2}}{\text{H}}_{\text{4}}{\text{Cl}}_{\text{2}\left(\text{g}\right)}{\text{+Cl}}_{\text{2(g)}}\stackrel{\text{uv-light}}{\to }{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3(g)}}{\text{+HCl}}_{\left(\text{g}\right)}\\ \text{Dichloroethane}\text{Trichloroethane}\end{array}$

  $\begin{array}{l}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}\left(\text{g}\right)}{\text{+Cl}}_{\text{2(g)}}\stackrel{\text{uv-light}}{\to }{\text{C}}_{\text{2}}{\text{H}}_{\text{2}}{\text{Cl}}_{\text{4(g)}}{\text{+HCl}}_{\left(\text{g}\right)}\\ \text{Trichloroethane}\text{Tetrachloroethane}\end{array}$

  $\begin{array}{l}{\text{C}}_{\text{2}}{\text{H}}_{\text{2}}{\text{Cl}}_{\text{4}\left(\text{g}\right)}{\text{+Cl}}_{\text{2(g)}}\stackrel{\text{uv-light}}{\to }{\text{C}}_{\text{2}}{\text{HCl}}_{\text{5(g)}}{\text{+HCl}}_{\left(\text{g}\right)}\\ \text{Tetrachloroethane}\text{Pentachloroethane}\end{array}$

  ${\text{C}}_{\text{2}}{\text{HCl}}_{5\left(\text{g}\right)}{\text{+Cl}}_{\text{2(g)}}\stackrel{\text{uv-light}}{\to }{\text{C}}_{\text{2}}{\text{HCl}}_{\text{6(g)}}{\text{+HCl}}_{\left(\text{g}\right)}$

The products are not optical isomers to each other.