Synthesis, Spectroscopic Characterization, and Conformational Properties of Trichloromethanesulfenyl Acetate, CCl₃SOC(O)CH₃

Abstract

Trichloromethanesulfenyl acetate, CCl 3SOC(O)CH 3, belongs to the family of sulfenic esters. This molecule has been characterized by vibrational spectroscopy. The conformational and geometrical properties of this species have been determined by IR and Raman spectroscopy, X-ray diffraction, and quantum chemical calculations. Geometry optimizations of the most stable forms were performed with ab initio (HF, MP2) and density functional theory (B3LYP) methods. According to our data, this compound results in a gauche-syn conformer with C 1 symmetry (gauche orientation around the S-O bond and syn orientation of the CO double bond with respect to the S-O single bond) for the most stable geometry, and trans-syn conformer with C s symmetry (trans orientation around the S-O bond and syn orientation of the CO double bond with respect to the S-O single bond) for the second stable conformer (1.1 and 0.53 kcal/mol higher in energy than the most stable C 1 form according to the matrix FTIR spectroscopy and MP2/6-31G* level of the theory, respectively). The crystalline solid (monoclinic, P2 1/ n, a = 8.0152(17) A, b = 5.7922(13) A, c = 17.429(4) A, alpha = gamma = 90 degrees , beta = 100.341(3) degrees ) consists exclusively of the main form. The geometrical parameters (X-ray diffraction) are d C-Cl = 1.767(19) A, d C-S = 1.797(2) A, d S-O = 1.663(14) A, d CO = 1.189(2) A, d O-C = 1.389(3) A, d C-C = 1.483(3) A, angles Cl-C-Cl = 110.3(11) degrees , Cl-C-S = 111.8(12) degrees , C-S-O = 97.4(8) degrees , S-O-C = 116.7(11) degrees , O-CO = 122.8(19) degrees , OC-C = 127.1(2) degrees , and the main torsion angles are delta(CSOC) = 105.9(15) degrees and delta(SOC(O)) = 7.6(3) degrees . The geometrical data calculated with B3LYP/6-31G++(3df,3pd), B3LYP/6-311G++(3df,3pd), B3LYP/aug-cc-pVTZ, and MP2/6-31G* are in good agreement with diffraction data.

Spectroscopic Characterization and Conformational Properties of S‐(Fluoroformyl)‐O‐(acetyl) Thioperoxide and S‐(Fluoroformyl)‐O‐(trifluoroacetyl) Thioperoxide

“…In the case of sulfenic esters and disulfides (Y = OR or SR), the preferred mutual orientation of the C=O and S-Y bonds is syn [10,11,17,18,21] as well. It is also known that in thioperoxides (Y = OR) the trans conformation at the S-O bond may be a second stable form.…”

“…It is also known that in thioperoxides (Y = OR) the trans conformation at the S-O bond may be a second stable form. [10,11] This phenomenon was observed by gas electron diffraction (GED) with CF 3 SOC(O)CH 3 [11] and CF 3 SOC(O)CF 3 [11] and by matrix IR spectroscopy with [a]…”

“…It was assigned by taking into account the similar band position in other S-O containing compounds such as CF 3 C(O)SOC(O)CF 3 [18] (783 cm -1 , IR), CF 3 SOC(O)CF 3 [24] (765 cm -1 , Raman), CF 3 SOC(O)CH 3 [24] (762 cm -1 , Raman), and CCl 3 SOC(O)-CH 3 [10] (757 cm -1 , Raman). When the FC(O)SOC(O)CH 3 /Ar mixture was heated to temperatures higher than 20°C and deposited as a matrix at 15 K, new bands appeared in the IR spectra.…”

“…In the IR (gas) spectrum of FC(O)SOC(O)CH 3 three bands are observed in the CH stretching region at 3038, 3002, and 2957 cm -1 , which are assigned to ν as (CH 3 ), ν as (CH 3 ), and ν s (CH 3 ) by comparison with values obtained from CCl 3 SOC(O)CH 3 [10] and CF 3 SOC(O)CH 3 . [24] Typical shapes and intensities of the CH 3 group are observed in the Raman spectrum of the liquid, and the bands at 3033, 2996, and 2945 cm -1 are attributed to the same modes.…”

“…This preferred conformation can be explained by taking into account anomeric effects. [8][9][10] However, some sulfenic esters of the type R 1 SOC(O)R 2 exhibit a trans conformation as the second stable form at room temperature, which has been identified by IR spectroscopy [10,11] and gas electron diffraction (GED). [11] This planar structure is possibly stabilized by the mesomeric effect (one sp 2 hybridized atom attached to the S-O bond).…”