Chapter 12, Problem 12B.1ST

Interpretation Introduction

Interpretation:

The feature that can be assigned to the $\text{CHO}$ proton has to be stated.

Concept introduction:

The NMR frequency of a given molecule depends upon its nuclear environment.  The chemical shift of a nucleus is the difference between its resonance frequency and that of a reference standard.  The standard for ${}^1\text{H}$ and ${}^{13}\text{C}$ is trimethylsilane, known as TMS.

Answer to Problem 12B.1ST

The feature that can be assigned to the $\text{CHO}$ is $\delta =\underset{\_}{9.80}$.

Explanation of Solution

Ethanal (${\text{CH}}_{\text{3}}\text{CHO}$) has two types of protons.  Therefore, it shows two lines in the NMR spectra, one at $\delta =2.20$ and other at $\delta =9.80$.

The proton of the $\text{CHO}$ will more deshielded than the proton of ${\text{CH}}_{\text{3}}$ .

Therefore, the $\text{CHO}$ proton will have a line at $\delta =\underset{\_}{9.80}$.