UV spectroscopic analysis of substituted 1,2,4-trioxanes. Theoretical and experimental study of cis-6-phenyl-5,6-(2-phenylpropylidene)-3,3-tetramethylene-1,2,4-trioxacyclohexane, cis-6-(4-fluorophenyl)-5,6-(2-(4-fluorophenyl)-propylidene)-3,3-tetramethylene-1,2,4-trioxacyclohexane and cis-6-(-4-methylphenyl)-5,6-(2-(4-methylphenyl)-propylidene)-3,3-tetramethylene-1,2,4-trioxacyclohexane molecules

A theoretical and experimental study Of cis-6-phenyl-5,6-(2-phenylpropylide ne)-3,3-tetramethylene-1,2,4-trioxacyclohexane, cis-6-(-4-fluorophenyl)-5,6 -(2-(4-fluorophenyl)-propylidene)-3,3 tetramethylene-1,2,4-trioxacyclohexan e, and cis-6-(4-methylphenyl)-5,6-(2-(4-methylphenyl)-propylidene)-3,3-tetr amethylene-1,2,4-trioxacyclohexane molecules is presented. Twisted-chair co nformations were found to be the most stable ones according molecular dynam ics simulations and density functional calculations. These findings were su pported by the comparison of the electronic spectra obtained in n-hexane so lution with the time dependent density functional calculations performed on the stable conformers. The experimental electronic spectrum of the methyl derivative, however, suggests that another conformer should be very close i n energy to the twisted-chair one. (C) 2001 Elsevier Science BN. All rights reserved.