INFRARED-SPECTRA OF POLYCYCLIC AROMATIC-HYDROCARBONS - METHYL SUBSTITUTION AND LOSS OF H

The B3LYP approach, in conjunction with the 4-31G basis set, is used t o compute the harmonic frequencies of 1- and 2-methylnaphthalene, 1-, 2-, and 9-methylanthracene, and their cations. The IR spectra of the m ethyl substituted species are very similar to the parent spectra, exce pt for the addition of the methyl C-H stretch at lower frequency than the aromatic C-H stretch. The loss of a single hydrogen from naphthale ne, anthracene, and their cations is shown to have a very small effect on the IR spectra. Loss of a methyl hydrogen from 1- or 2-methylnapht halene, or their cations, is shown to shift the side group C-H frequen cies from below aromatic hydrogen stretching frequencies to above them . The loss of H from 2-methylenenaphthalene shows only a small shift i n the side group C-H stretching frequency. (C) 1998 Elsevier Science B .V. All rights reserved.