Chapter 16, Problem 16.25P

Interpretation Introduction

Interpretation:

The splitting diagram for each ${\text{H}}_{\text{A}}$ and ${\text{H}}_{\text{C}}$ in bromoethene is to be constructed.

Concept introduction:

A complex splitting pattern is observed when a proton is coupled with two or more chemically disctinct protons. When a given proton is coupled with two types of chemically distinct protons, two independent splitting patterns appear simultaneously.

The size of the vicinal coupling constant between trans protons on a double bond is normally larger than that between cis protons. For the compounds in which vicinal protons are not equivalent, a proton ${\text{H}}_A$ is coupled with ${\text{H}}_{\text{B}}{\text{, H}}_{\text{C}}\text{, etc}\mathrm{..}$ with unequal coupling constants. The original signal for ${\text{H}}_A$ is split into $\text{(n+1)}$ peaks by ${\text{nH}}_{\text{B}}$ protons. Each of these lines is further split into $\text{(n+1)}$ peaks by ${\text{nH}}_{\text{C}}$ protons.