Chemistry

Catherine E. Housecroft, Edwin C. Constable

ISBN #9780273715450

4th Edition

995 Questions

13,222 Students Helped

Homework Questions

Summary

Learning Objectives

Key Concepts

Example Problems

Explanations

Common Mistakes

Summary

NMR spectroscopy is a powerful analytical tool that leverages the magnetic properties of nuclei to elucidate molecular structures. The technique relies on understanding nuclear spin states, resonance frequencies, and chemical shift variations, and requires careful sample and solvent preparation. Mastery of these concepts allows for accurate interpretation of NMR spectra and can significantly aid in the identification and characterization of chemical compounds.

Learning Objectives

Key Concepts

CONCEPT

DEFINITION

Acyclic and cyclic alkanes

A discussion of both open?chain (acyclic) and ring (cyclic) saturated hydrocarbons, emphasizing their structural features, nomenclature, conformational behavior (including ring strain and conformation), and the processes used in their interconversion and synthesis.

Example Problems

Example 1

Using the data in Table $14.1,$ determine the resonance frequency of $^{31} \mathbf{P}$ nuclei on a $400 \mathrm{MHz}$ spectrometer, and the resonance frequency of $^{13} \mathrm{C}$ nuclei on a $250 \mathrm{MHz}$ instrument.

Example 2

The $^{13} \mathrm{C}$ NMR spectrum of acetic acid (14.15) has signals at $\delta 20.6$ and 178.1 ppm. Assign the spectrum. (FIGURE CAN'T COPY)

Example 3

The 's C NMR spectrum of 2-methylpropan-2-ol (14.16) has signals at 831.2 and 68.9 ppm. Suggest assignments for these signals. What other feature of the spectrum would confirm the assignments?

Example 4

The $^{13}$ C NMR spectrum of 14.17 possesses signals of approximately equal intensities at $\delta 20.5,52.0$ 80.8 and 170.0 ppm. Suggest assignments for the spectrum. (FIGURE CAN'T COPY)

Example 5

Compounds 14.18 and 14.19 are isomers of butyne. The $^{13}$ C NMR spectra of the two isomers are shown in Figure $14.16 .$ (a) Which spectrum belongs to which compound? (b) Assign the signals. (FIGURE CAN'T COPY)