OXIDATION OF TELLUROPYRYLIUM DYES WITH OZINE, CHLORINE, AND BROMINE -DIFFERING REGIOCHEMICAL AND KINETIC-BEHAVIOR WITH RESPECT TO OXIDATIONS OF OXYGEN-CONTAINING, SULFUR-CONTAINING, AND SELENIUM-CONTAINING DYES

Oxidations of telluropyrylium dyes 1-3 with ozone in water, chlorine i n carbon tetrachloride, or bromine in carbon tetrachloride gave second -order rate constants of greater-than-or-equal-to 10(9) L mol-1 s-1 us ing stopped-flow techniques to measure rates of oxidation. Aqueous ozo ne gave initial oxidation of the tellurium atoms of 1-3 to produce hyd roxytelluranes 4-6, respectively. Oxidative addition of chlorine or br omine across a tellurium atom of 1-3 gave the corresponding tellurium( IV) dihalides. With excess ozone, a second oxidation was observed with a second-order rate constant of (1.3 +/- 0.1) X 10(6) L mol-1 s-1. Ch alcogenopyrylium dyes 7-10 which contain only oxygen, sulfur, and/or s elenium heteroatoms reacted with smaller rate constants for oxidation. Chlorine and bromine gave second-order rate constants within 1 order of magnitude of those of telluropyrylium dyes for reactions with 7-10. Ozone was more than 100 000 times less reactive toward chalcogenopyry lium dyes 7-9 relative to telluropyrylium dyes 1-3 with second-order r ate constants (1.1 +/- 0.1) X 10(4) L mol-1 s-1 for 7, (8.5 +/- 0.9) X 10(3) L mol-1 s-1 for 8, and (5.4 +/- 0.6) X 10(3) L mol-1 s-1 for 9. With dyes 7-10, ozone destroyed the pi-framework of the dye while chl orine and bromine gave mono- and dihalogenation of the trimethine brid ge of the dye.