Chapter 15.17, Problem 37P

Interpretation Introduction

Interpretation:

To predict which will have higher chemical shift value for the $\text{OH}$ proton, ${}^{\text{1}}\text{H NMR}$ spectrum of pure ethanol or ${}^{\text{1}}\text{H NMR}$ spectrum of ethanol dissolved in ${\text{CH}}_{\text{2}}{\text{Cl}}_{\text{2}}$.

Concept introduction:

Depending upon the electron density or the concentration of electron around the proton the chemical shift values of the proton varies relative to the reference signal.

The more the shielded proton less will be its chemical shift value and the corresponding signal will be produced at the right-hand side or lower frequency region.

The more the deshielded or less shielded proton more will be its chemical shift value and the corresponding signal will be produced at the left-hand side or higher frequency region.

Proton or set of proton attached near to the more electronegative or electron withdrawing atoms is more deshielded or less shielded and vice versa.  The presence of hydrogen bonding in the compound also affects the chemical shift values.  The hydrogen bonding causes the decrease in electron density around the proton and causes deshielded due to which the signal for the proton is observed at a higher frequency.