Chapter A, Problem 1PP

Interpretation Introduction

Interpretation:

The structure of the compound with molecular formula ${\text{C}}_5{\text{H}}_{10}\text{O}$ is to be proposed with the help of given data.

Concept introduction:

Mass spectrometry is a technique used for measuring the masses of atoms and molecules with great accuracy.

In a mass spectrometer, the vapor of organic compound is bombarded with a beam of high energy electrons that makes the neutral molecule lose an electron and converts it to a radical cation known as a molecular ion.

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

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

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.

${}^{13}\text{C}$ NMR is only used in the observation of isotopes of carbon atoms.

The peak at $\delta 211.0$ supports the existence of a carbonyl group in the compound.

The peak at $\delta 37$ represents the $-{\text{CH}}_2-$ group.

The peak at $\delta 10$ shows the $-{\text{CH}}_3$ group.

Answer to Problem 1PP

Solution: The structure of the compound with molecular formula ${\text{C}}_5{\text{H}}_{10}\text{O}$ is as:

Explanation of Solution

The figure given below represents the ${}^{13}\text{C}$ spectrum of the compound with the molecular formula ${\text{C}}_5{\text{H}}_{10}\text{O}$.

In DEPT ${}^{13}\text{C}$ spectra, the peaks present at different regions are as:

The peak at $\delta 211.0$ supports the existence of a carbonyl group in the compound.

The peak at $\delta 37$ represents the $-{\text{CH}}_2-$ group.

The peak at $\delta 10$ shows the $-{\text{CH}}_3$ group.

The presence of two signals in the alkyl group region indicates the presence of symmetry in the compound and the two unique carbon atoms.

Therefore, the structure of the compound is as:

Conclusion

The structure of the compound with molecular formula ${\text{C}}_5{\text{H}}_{10}\text{O}$ is as: