Question

please help me analyze these IRs the first one is 1-butanol, the second one is 2t-butanol, and the third one is 2-pentanol.

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Answer 1

1. The IR spectrum of 1-butanol showing a broad and strong peak centered at 3300cm-1 is due to O-H stretching absorption. This broad peak in the region of 3600-3200 cm-1 is the characteristic peak of alcohols and its is due to intermolecular H-bonding in alcohols

Three sharp peaks at 2960, 2933 and 2850 cm-1 are due to asymmetric ans symmetric stretching of sp3 C-H absorptions and the corresponding C-H bends are observed at 1465 and 1380 cm-1

A strong peak at 1050cm-1 is due to C-O stretching absorption

2. The IR spectrum of 2-butanol showing a broad and strong peak centered at 3300cm-1 is due to O-H stretching absorption. This broad peak in the region of 3600-3200 cm-1 is the characteristic peak of alcohols and its is due to intermolecular H-bonding in alcohols

Three sharp peaks at 2960, 2933 and 2850 cm-1 are due to asymmetric ans symmetric stretching of sp3 C-H absorptions and the corresponding C-H bends are observed at 1465 and 1380 cm-1

A strong peak at 1100cm-1 is due to C-O stretching absorption. The C-O absorption of secondary alcohol is slightly larger than primary alcohol

3. The IR spectrum of 1-butanol showing a broad and strong peak centered at 3330cm-1 is due to O-H stretching absorption. This broad peak in the region of 3600-3200 cm-1 is the characteristic peak of alcohols and its is due to intermolecular H-bonding in alcohols

Three sharp peaks at 2965, 2930 and 2855 cm-1 are due to asymmetric ans symmetric stretching of sp3 C-H absorptions and the corresponding C-H bends are observed at 1465 and 1380 cm-1

A strong peak at 1055cm-1 is due to C-O stretching absorption.

These three alcohols shows same absorption patterns in theirs IR spectrum in functional group regions (4000-1500cm-1) however they can be distinguished in the finger print region.