Cresols—An investigation into their electronic structure and spectra

The three isomeric cresols were subjected to the all-valence-electron CNDO/2 andPPP-CI calculations. Results from this study were used:

1. to compare the electronic structures of these isomers vis-à-vis parent compounds—phenol and toluene,
2. to obtain a quantitative picture of their chemical reactivities and electronic absorption spectra.

Using the σ-core charges derived from CNDO/2 calculations and subsequently revising the valence-state ionisation potential and one-center-two-electron repulsion integrals, thePPP-CI calculations were performed on the title compounds according toNishimoto andForster scheme. In these calculations the pseudo-unsaturated nature of the methyl group has been given due consideration. In spectral assignment, compared to the conventionalPPP approach, the CNDO/2-basedPPP-CI method gave a better agreement with the experimental data.