Compare the IR spectrum of benzoin ) with the IR spectrum of benzil . Explain how the changes in the important peaks are related to the differences between the two

Question

structures.

Answer 1

The IR spectra of benzoin and benzil are both characterized by strong peaks in the range of 3000-3500 cm-1, which correspond to the stretching of the C-H bonds in the aromatic ring. However, the IR spectrum of benzoin also has a strong peak at 1720 cm-1, which corresponds to the C=O stretching of the ketone group. This peak is absent in the IR spectrum of benzil, which instead has a strong peak at 1620 cm-1, corresponding to the C=C stretching of the double bond. This difference is due to the fact that benzoin has a ketone group, while benzil has a double bond.