Question

consider the ir spectrum of an unknown compound. an ir spectrum, with a large stretch at 1685 inverse centimeters. there are no key stretches with higher wavenumbers. there is a series of minor stretches around 1500 to 1600. there is nothing at 1650. compound a contains two conjugated alkenes. compound b is a benzene ring with an aldehyde substituent. compound c is an aldehyde bound to a propyl group. compound d contains a cyclohexane with three carbonyl groups on carbons 1, 3 and 5. compound e is a cyclic amide with two conjugated double bonds. compound f has two aryl ketones. which compound matches the ir spectrum best

Answer 1

Compound B, which is a benzene ring with an aldehyde substituent, matches the IR spectrum best. This is because the large stretch at 1685 inverse centimeters indicates the presence of a carbonyl (C=O) group, which is characteristic of aldehydes. Additionally, the absence of any key stretches at higher wavenumbers suggests the absence of additional functional groups. Compound B satisfies these criteria as it contains both a benzene ring and an aldehyde group.