Chapter A, Problem 4PP

Interpretation Introduction

Interpretation:

The number of ${}^{13}\text{C NMR}$ signals of the given compounds is to be predicted.

Concept Introduction:

In ${}^{13}\text{C NMR}$, the carbon atom equivalent as per the molecular symmetry produces one signal.

In ${}^{13}\text{C NMR}$, each carbon atom with a different environment in a compound gives one signal.

The number of signals in the spectrum shows the number of different protons or atoms present in the molecule.

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.

Few elements, such as ${}^{13}{\text{C and }}^1\text{H}$, have nuclei behaving as magnets about an axis. These elements are placed in magnetic field irradiated with electromagnetic energy of specific frequency and the nuclei tend to absorb energy via magnetic resonance. There is this graph that shows energy absorption frequencies and intensities of a sample kept in the magnetic field called nuclear magnetic resonance (NMR).

In $\text{NMR}$ spectroscopy, the proton nuclear magnetic resonance ${(}^{\text{1}}\text{H}\text{NMR)}$ is used to find out the structure of molecules with the help of ${}^{\text{1}}\text{H}$ atom within the molecules.

Induced magnetic field consists of electricity generated from movement in a magnetic field.

The position of a signal on x-axis in the $\text{NMR}$ spectrum depicts the chemical shift expressed in $\delta$ or $\text{ppm}$.

The number of signals in $\text{H}\text{ NMR}$ spectrum represents the number of different chemical environments for the protons.

The area covered by the signal is proportional to the number of equivalent protons causing the signal.

The hydrogen atoms on adjacent carbon atoms split the signal into two or more peaks. One, two or three hydrogen atoms split the signal into two, three or four peaks described as doublet, triplet or quartet respectively.

A decrease in the electron density around a proton deshields the signal downfield at a larger value of chemical shift.

An increase in electron density shields the signal upfield at a lower value of chemical shift.