15. Analytical Techniques:IR, NMR, Mass Spect

Rank the following compounds from highest wavenumber to lowest wavenumber for their C=O absorption band:

For each of the following pairs of compounds, identify one IR absorption band that could be used to distinguish between them:

i.

j.

a. How could you use IR spectroscopy to determine whether the following reaction had occurred?

b. After purifying the product, how could you determine whether all the NH₂NH₂ had been removed?

How can IR spectroscopy be used to distinguish between the following compounds?

e. cyclohexene and cyclohexane

f. a primary amine and a tertiary amine

Rank the following compounds from highest wavenumber to lowest wavenumber for their C-O absorption band:

The IR spectrum for anisole contains two C―O stretching bands in the fingerprint region. Match the band to the bond that gives rise to it. Why are these bands so intense?

<IMAGE>

Identify the important bands you would expect to find in an IR spectrum for the following molecules.

(a)

A carboxylic acid can be converted to an ester using the conditions shown. Explain how a comparison of an IR spectrum of the reactant(s) and product can be used to determine whether the reaction was successful or not.

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

e.

f.

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

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

c.

d.

Identify the important bands you would expect to find in an IR spectrum for the following molecules.

(c)

Answer each of the following questions based on the images below.

a) Which compounds show an intense peak ~ 1700 cm^-1?

b) Which compound shows an intense, broad peak at ~ 3400 cm^-1?

c) Which compound has a peak at ~1700 cm^-1, but no peaks at 2700 cm^-1?

d) Which compound has no signal beyond the fingerprint region?