ISSN:
0947-6539
Keywords:
ab initio calculations
;
rotamers
;
stereoisomers
;
sulfane oxides
;
torsional potentials
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Ab initio MO calculations (MP 2/6-311 G**//HF/6-311 G**) have been performed for several isomers (including rotamers) of Me2S3O and Me2S3O2. MeS(O)SSMe exists as five rotamers; the most stable form (1a) has a helical backbone CSSSC with S-S bond lengths of 206.0 (SIISII) and 212.4 pm (SIISII). The most stable rotamer of MeS-S(O)SMe (2a), is less stable than 1a by 10.7 kJ mol-1; it is of Cs, symmetry, while a rotamer of Cs symmetry (2b) is less stable than 2a by only 1.4 kJ mol-1. Both 2a and 2b are stabilized by O ⃛ H hydrogen bonds. The S-S bond lengths of 2a are 210.0 and 212.0 pm; the CSSSC chain is not helical (CSSS torsion angles 166.3 and -75.4°). The 1,3-dioxide MeS(O)-SS(O)Me (3) has two equivalent chiral centers and exists as diastereomers. The most stable isomer 3a (RR)/(SS) is of C2 symmetry with methyl groups trans to each other; the SO bonds form an angle of about 90°. The meso form 3b is less stable than 3a by 17.2 kJ mol-1 and the rotamers 3c and 3d are less stable by 25.6 kJ mol-1 and 28.4 kJ mol-1, respectively. The trisulfane-1.2-dioxide MeS(O)-S(O)SMe has two nonequivalent chiral centers and exists as five isomers. The most stable form, the (RS)/(SR) form 4a, is less stable than 3a by 21.4 kJ mol-1 and is characterized by SS bonds of 220.9 (SIIISIII) and 208.3 pm (SIIISII). The rotamer 4b is less stable by 5.9 kJ mol-1. The isomers 4c, 4d, and 4e are all of (SS)/(RR) configuration and are less stable than 4a by 6.3, 12.7, and 12.0 kJ mol-1. For comparison, ab initio MO calculations (HF/6-311 G*) for tBuS(O)SS(O)-tBu yielded two diastereomers of practically identically energy that both contain helical CSSSC backbones. The (RS) form is less stable than the (RR)/(SS) form by 1.8 kJ mol-1.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/chem.1460020903
Permalink
