Predict the characteristic infrared absorptions of the functional groups in the following molecules.
(a) cyclohexene
(b) pentan-2-ol
(c) pentan-2-one

Spectra are given for three compounds. Each compound has one or more of the following functional groups: alcohol, amine, ketone, aldehyde, and carboxylic acid. Determine the functional group(s) in each compound, and assign the major peaks above 1600 cm^–1.

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A common lab experiment is the dehydration of cyclohexanol to cyclohexene.

(a) Explain how you could tell from the IR spectrum whether your product was pure cyclohexene, pure cyclohexanol, or a mixture of cyclohexene and cyclohexanol. Give approximate frequencies for distinctive peaks.

(b) Explain why mass spectrometry might not be a good way to distinguish cyclohexene from cyclohexanol.

Four infrared spectra are shown, corresponding to four of the following compounds. For each spectrum, determine the structure and explain how the peaks in the spectrum correspond to the structure you have chosen.

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Predict the characteristic infrared absorptions of the functional groups in the following molecules.

(d) pent-1-yne

(e) diethylamine

(f) pentanoic acid

These five structures all have distinguishing absorptions in the IR. Match each structure with its characteristic absorption.

(a) sharp, 2254 cm^–1

(b) very broad, centered about 3330 cm^–1

(c) strong, slightly broadened, 1645 cm^–1

(d) broad with spikes at 3367 and 3292 cm^–1

(e) strong, sharp 1717 cm^–1

Three common lab experiments are shown. In each case, describe how the IR spectrum of the product would differ from that of the reactant. Give approximate frequencies for distinctive peaks in the IR spectrum of the reactant and also that of the product.

Give approximate wavenumbers for the major characteristic IR absorption bands that would be given by each of the following compounds:

e.

f.

For each of the following pairs of compounds, name one absorption band that can be used to distinguish between them.

e.

f.