Chapter 28.8, Problem 7P

Interpretation Introduction

Interpretation:

An explanation is to be suggested for the observation that branches shorter or longer than four carbonsare found infrequently in polyethylene.

Concept introduction:

During the intramolecular hydrogen transfer, the carbon atom at the end of the polymer chain, which has one unpaired electron, abstracts a hydrogen atom from the

fifth carbon.

This results in a transition state which is a cyclic arrangement of six atoms.

This reduces the randomness of the transition state as compared to the open chain polymer.

During this process, a primary free radical is converted to a more stable secondary free radical.

This step is exothermic since products of this step are more stable than the reactants.