Frontier density pattern of dioxins

Ab initio molecular orbital calculations are performed to estimate the electron densities of the highest occupied molecular orbitals (HOMO) of 75 congeners of chlorinated dibenzo-p-dioxins and a nonchlorinated dibenzo-p-dioxin. Electron densities of HOMO on out of plane π orbitals of 12 carbons and two oxygens in the dioxin structure are used as variables in multivariate statistical analysis. Principal component analysis can classify 76 congeners of dioxins according to the principal component scores. All of the most toxic dioxins are involved in the group that has large negative values for both the first and the third principal component scores.