Infrared absorption spectra of the vapors of methoxybenzoic and nitrobenzoic acid isomers

The IR absorption spectra (400-4000 cm(-1)) of vaporous methoxybenzoic and nitrobenzoic acids were measured over the temperature range similar to 160- 190 degrees C. The vibrational bands of the spectra were identified. It was found that, in the vaporous state, all isomers of methoxybenzoic and nitro benzoic acids occur as monomers. It was shown that the monomers of o-nitrob enzoic acid have a planar structure, with the carbonyl occupying the trans- position. In the vapor of o-methoxybenzoic acid, monomers with intermolecul ar bonds and planar monomers with free hydroxy groups were found.