Light absorption studies: part I. The ultraviolet absorption spectra of some nitrobenzenes. Part II. The ultraviolet absorption spectra of some benzaldehydes

Abstract

Part 1. The electronic spectra of nitrobenzenes are discussed in terms of previously proposed hypotheses relating electronic interactions and ultraviolet absorption data. A previously suggested order of mesomeric interaction of the halogens is confirmed, and it is shown that the mesomeric effect of the nitro-group is greater than that of the acetyl-group. -- Part 2. The electronic spectra of benzaldehydes are recorded and discussed in terms of previously proposed hypotheses. The formyl- group is shown to endow benzene derivatives with similar properties to those of nitro- and acetyl-substituted derivatives, save that the effects of steric interactions and hydrogen bonding are slightly modified. An order of mesomeric interaction -NO ₂ > -CHO > -COCH₃ > -COOH is proposed.