Chapter 9, Problem 1PP

Interpretation Introduction

Interpretation:

The range of chemical shifts in the given compound is to be determined.

Concept introduction:

Nuclear magnetic resonance (NMR) is one of the most capable analytical techniques used for determining the functional groups and how the atoms are structured and arranged in a molecule.

A compound containing protons or carbon-13 when placed under very strong magnetic field and treated with electromagnetic energy radiation of suitable frequency, the nuclei of the compound absorb energy through a process called magnetic resonance.

Nuclear magnetic resonance spectroscopy is a graph showing characteristic energy absorption frequencies and intensities of a compound under magnetic field.

Chemical shifts are positions of signals along the x-axis in the nuclear magnetic spectroscopy. It gives an idea on how many different hydrogen atoms are present in a given H-NMR for a particular compound.

More electronegative atoms attached to the group, more the protons are deshielded; more will be the chemical shift value.

Answer to Problem 1PP

Solution:

Chemical shifts for ethyl acetate are at $0.8-1.2\text{ ppm, }2.0-2.6\text{ ppm, and }3.3-3.9\text{ ppm}$.

Explanation of Solution

Structure of ethyl acetate ${\text{CH}}_{\text{3}}{\text{CO}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$ is as follows:

From the structure, we have three types of hydrogens and from table 9.1 chemical shifts result in the values as follows:

$\begin{array}{c}-C{H}_3:0.8-1.2{\text{ ppm (H}}_{\text{a}}\text{)}\\ -COC{H}_3-:2.0-2.6\text{ ppm }(H_{\text{b}})\\ -CO-C{H}_2-:3.3-3.9{\text{ ppm (H}}_{\text{c}})\end{array}$

Conclusion

The chemical shifts are in the ranges of $0.8-1.2\text{ ppm, }2.0-2.6\text{ ppm, and }3.3-3.9\text{ ppm}$.