[maakii]

Hi everyone,

I have a question about the UV spectrum of benzoic acid. The spectrum has 3 maxima at 230, 272 and 282 nm. The peaks at 230 and 272 are due to the benzene moiety which is conjugated with the -COOH group. However, I am not sure about the peak at 282 nm.

Can I independently take the carbonyl (C=O) group of the COOH group, and say that the peak at 282 is due to the n->pi star transition, since C=O groups have n->pi star transitions at about 290nm? Or would you have to take the COOH group as a whole i.e. the C=O group cannot be looked at in isolation, and must be treated as part of the COOH functional group?

The peak at 282 is not due to the n->pi star transition, does anyone know what transition it corresponds to? Thank you in advance!