The functional groups in an organic compound can frequently be deduced from its

Question

The functional groups in an organic compound can frequently be deduced from its infrared absorption spectrum. A compound that contains C, H, and O exhibits no absorption above 3000 cm-1 or in the 1800-1650 region, but exhibits strong absorption at 1140 cm-1. Relative absorption intensity: (s)=strong, (m)=medium, (w)=weak. What functional class(es) does the compound belong to? List only classes for which evidence is given here. Attach no significance to evidence not cited explicitly. Do not over-interpret exact absorption band positions. None of your inferences should depend on small differences like 10 to 20 cm-1. The functional class(es) of this compound is(are)

Explanation / Answer

Answer:

An Unknown organic compound contains only C, H & O. Hence possible functional group are -OH (Alcohol/phenol), Ether, Ester etc.

a) Evidence 1: No IR Absorption above 3000 cm-1.

Conclusion: Functionality like alcohol/phenol -O-H absent because for such a functionality absorption above 3000 cm-1 is expected which is absent.

b) Evidence: NO Absorption in the range 1800-1650 cm-1 indicates an absence of Aromatic/olefinic C=C group, Carbonyl C=O, Carboxylic acid r derivative absent.

c) Evidence: Absorption at 1140 cm-1 indicates C-O stretch for Ether.

Answer: Most probably, an Aliphatic Ether compound is present.

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