Question

Tell how IR spectroscopy can be used to differentiate the following compounds. in each case, indicate the significant IR bands that will be observed and their approximate wavenumbers

a) 1-butanol, 2-butanol, and 2-methyl-2-butanol

b) ortho-xylene, meta-xylene, and para-xylene

c) butanal, 1-butanol, 2-butanone, butanoic acid, and butyl acetate

Answer 1

a) All alcohol maximmum give IR peack is 3000 Cm-1. The gien compounds difference we can obsere their broad and narrow peaks in spectrum.

1-butanol will not give free O-H narrow peaks but 2-butanaol give free O-H peaks.You can obseve the below images.

For 1-butanol

2-butanol:

In 2-methyl-2-butanol will give broad peaks in range 1000- 1500 cm-1. this will not come 1-butanol and 2-butanol. see the difference below

B)

1. o-xylene 735-770 ortho
2. p-xylene 810-840(m) para
3. m-xylene meta 690-710, 750-810(m)

The above range we can differentiate the compounds.

C) In 2-butanone The strong stretch at 1670-1820 cm-1

butanoic acid willl give stretch at

C=O	stretch	1700-1725	strong
O-H	stretch	2500-3300	strong, very broad
C-O	stretch	1210-1320	strong

butyl acetate

C=O	stretch	1735-1750	strong
C-O	stretch	1000-1300	two bands or more