Question

Label the stretches in the IR spectrum shown that confirm the presence of benzil in the sample. Then identify a stretch that would indicate the presence of starting material (benzoin).

Identify which of the following stretches would indicate the starting material (benzoin) is still present?

Answer 1

The structure of benzyl is as follows: Benzil A peak at 3100 cm1 corresponds to sp C-H stretching. A peak at 1640 cm1 corresponds to sp C-O stretching. A peak at 1575 cm1 corresponds to sp2 C-C stretching. The structure of benzoin is as follows: он benzoin

The only difference in the structure of benzyl and benzoin is the presence of OH group in benzoin So, the peak that indicates the presence of benzoin in the sample of benzyl is a broad stretching at 3300 cm-1.

Infrared Spcctrum of Benzi, KBr Identify which of the following stretches would indicate the 50 3100cm' spac-H starting material (benzoin) is still present? 45 40 narrow stretch at -3300 cm O broad stretch at-3300 cm1 narrow stretch at 1500 cm O broad stretch at -1700 cm1 35 30 25 20 4000 3500 000 2500 2000 1500 1000 Wavenumbers (em)