139408-38-1

-

This work reports the enthalpies of formation in the condensed and gas state of 1,4-dithiacyclohexane 1,1-dioxide (1,4-dithiane sulfone, 5), derived from the enthalpy of combustion in oxygen, measured by a rotating bomb calorimeter and the variation of vapor pressures with temperatures determined by the Knudsen effusion technique. The theoretically estimated enthalpy of formation was calculated from high-level ab initio molecular orbital calculations at the G2(MP2) level. The theoretical calculations appear to be in very good agreement with experiment. A comparison of the conversion of thiane sulfone 3 to 1,3-dithiane sulfone 4 and 1,4-dithiane sulfone 5 clearly shows the 1,3 isomer to be 6.7 kJ mol-1 less stable, probably owing to diminished electrostatic repulsion between the sulfur heteroatoms in 1,4-sulfone 5.

-

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 kT 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 P1? 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) ?, α = 90.46 (6), β= 97.04 (5), γ = 101.88 (6)°. 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.