The vibration of which bond gives an IR absorption that distinguishes between the following two compounds? CH3CH2CH2OH CH3CH2OCH3

Question

CH3CH2CH2OH CH3CH2OCH3

Answer options

O−H

C−H

C−C



C−O

Answer 1

The IR spectrum of a molecule provides information about its vibrational modes. In general, the IR spectrum of a molecule will contain characteristic peaks that correspond to specific functional groups and bond types.

In the case of the two compounds given, CH3CH2CH2OH and CH3CH2OCH3, the functional groups that distinguish them are the hydroxyl group (-OH) in CH3CH2CH2OH and the methoxy group (-OCH3) in CH3CH2OCH3.

The IR spectrum of a molecule containing an -OH group will typically show a broad, strong peak in the region of 3200-3600 cm-1, corresponding to the stretching vibration of the O-H bond. This peak is often called the "alcohol O-H stretch". Therefore, the vibration of the O-H bond in CH3CH2CH2OH would give an IR absorption that distinguishes it from CH3CH2OCH3.

In contrast, the IR spectrum of a molecule containing an -OCH3 group will typically show a sharp, strong peak in the region of 2800-3000 cm-1, corresponding to the stretching vibration of the C-H bond in the methyl group. This peak is often called the "methyl C-H stretch". Therefore, the vibration of the C-H bond in the methyl group of CH3CH2OCH3 would give an IR absorption that distinguishes it from CH3CH2CH2OH.

Based on this information, the correct answer is O-H.