Chapter 14.13, Problem 30P

Interpretation Introduction

Interpretation:

Reason for no coupling between the ‘a’ and ‘c’ protons or between the ‘b’ and ‘c’ protons in the cis and trans alkene of chloropropenoic acid has to be expalined.

Concept introduction:

The distance between the adjacent peaks obtained from the splitting of an NMR signal is known as coupling constant. It is denoted by J and I measured in Hertz.  The coupling constant is useful when the interpretation of a complex NMR spectrum has to be done. The value of the coupling constant is independent of the operating frequency of the spectrometer.

The coupling constant can be used to distinguish between the cis and trans isomer of the compound.  The trans isomer has a higher value of coupling constant than the cis isomer.  The coupling constant is generally very low for long-range coupling and is too small to visualize.