Reaction of SeOCF3 and SeO2CF3 groups with π-electron systems in ground and excited states

The dipole moments and ultraviolet spectra were measured for selenium compounds containing SeOCF₃ and SeO₂CF₃ groups. It is shown that in the ground state the SeO₂CF₃ group has a greater tendency toward conjugation with the -electron system of the benzene ring thandoes the SeOCF₃ group. In the ground state, selenium compounds containing SeOCF₃ and SeO₂CF₃ groups have a smaller conjugation effect than corresponding sulfur compounds. Oxidation of SeCF₃ to SeOCF₃ decreases the degree to which the uncollectivized electrons of selenium take part in conjugation with electron-accepting groups. In the unexcited state the free electrons of selenium in SeCH₃ and SeCF₃ groups are more mobile than those of sulfur in SCH₃ and SCF₃ groups, and the * level of the Se=O groups is lower than that of the S=O group.