Question

Which has a greater chemical shift for the proton, the proton H¹NMR spectrum of pure ethanol or the proton H¹NMR spectrum of ethanol dissolved in CH₂Cl₂.

Short answer

The H¹NMR spectrum of pure ethanol shows a greater chemical shift value than ethanol dissolved in CH₂Cl₂.

Step-by-step solution

Step-by-Step SolutionStep 1: Characteristics of pure ethanol H1NMR spectrum

Proton bonded to oxygen will show a higher frequency. This can be explained by the OH group of ethanol as it is split into triplets by the neighboring methylene proton. Methylene proton split into multiplet by its neighboring proton and OH proton.Thus, the signal for the OH proton is broad and easy to find in the spectrum.

Characteristics of ethanol dissolved in chloroform H1NMR spectrum

Proton attached to an acid or base undergoes proton exchange, which means alcohol and acid(base) exchange protons.This exchange of protons splits the proton into a singlet, which will not split the adjacent protons. Thus, the proton of ethanol dissolved in chloroform shows less chemical shift value than pure ethanol.