Chapter 26, Problem 26.77P

Interpretation Introduction

Interpretation:

Research in the “unzipping” of poly(vinyl chloride) indicates that certain defects in the polymer contribute to the rate of unzipping. These defects are arrangements of atoms that are different from the arrangements in the repeating units shown in the condensed formula. Researchers have found that defects involving allylic chlorides and tertiary chlorides, specifically, promote the reaction.

These observations from the mechanism for the “unzipping” of poly(vinyl chloride) is to be explained.

Concept introduction:

The “unzipping” of PVC follows $\text{E1}$ mechanism in acidic medium. So, the stability of the carbocation is a matter in this case. As the stability of the carbocation increases, the rate of $\text{E1}$ reaction increases. The process of cutting (scission) of the polymer to the corresponding monomer is known as unzipping. The stability order of carbocation is $\text{Primary < Secondary < Benzylic, allylic < Tertiary}\text{.}$