Ir Spectroscopy Worksheet With Answers (Page 2 of 2) in pdf

Ir Spectroscopy Worksheet With Answers Page 2

a) Identify the bonds present in the molecule?

Strong absorption around 3000 indicates C-H bonds while stron absorption at 1750 indicates

a C=O bond. Another strong absorption at 1250 should indicate the presence of possibly a

C-O bond.

The fact that we have no absorption in the region 2500 – 3300 (O-H of acid) indicates that

this is not an organic acid.

So from the IR spectrum we can deduce that it is possibly some kind of ester. The structure of

which should be easily derived from the

HNMR spectrum.

From the

HNMR spectrum we see 5 hydrogen environments.

b) Give a possible structural formula for the compound

Shown above

4) Below is the IR spectrum of an organic molecule.

A scientist suspects that it belongs to either of three molecules

CHOHCH

ii)

CHCHCH

iii)

COO H

Which molecule is likely to form the IR spectrum above? Discuss with reference to the IR

spectrum.

Looking at the IR spectrum we see a broad absorption band at wavelength 2200 – 2550

indicating an O-H

We also see no strong absorption in the region of 1610 - 1680 to indicate C=C bonds.

There is also no strong absorption in the region 1670 -1750 to indicate a C=O bond.

The spectrum is of pentan-2-ol (option i)

Ir Spectroscopy Worksheet With Answers Page 2