COMPARISON OF THE PHOTOOXIDATIONS OF 1,5-DITHIACYCLOOCTANE, 1,4-DITHIANE, AND PENTAMETHYLENE SULFIDE - ANOTHER EXAMPLE OF REMOTE PARTICIPATION DURING PHOTOOXIDATION AT SULFUR

The photooxidations of 1,5-dithiacyclooctane (1,5-DTCO), 1,4-dithiane, and pentamethylene sulfide have been compared. The photooxidation of 1,5-DTCO differs significantly from the other substrates in several respects: (1) the ratio of chemical quenching to total quenching of singlet oxygen during photooxidation of 1,5-DTCO is 70%, in comparison to 5% for 1,4-dithiane and 2.9% for pentamethylene sulfide; (2) a sulfone is produced in all of the photooxidations except in that of 1,5-DTCO; and (3) the value of k(T) is larger for 1,5-DTCO than for any previously reported sulfide. A novel sulfur-sulfur interaction during photooxidation of 1,5-DTCO is utilized in order to explain these results. A cis-bissulfoxide was isolated from the photooxidation of 1,5-DTCO. It crystallizes in space group P1BAR of the triclinic system with two molecules in a cell of the following dimensions: a = 5.348 (3), b = 6.755 (5), c = 11.677 (7) angstrom, alpha = 90.46 (6), beta = 97.04 (5), gamma = 101.88 (6)-degrees. The structure has been refined to a final value of 0.0477 for the conventional R factor on the basis of 951 independent observed intensities.