Matrix Photochemistry of CH₃C(O)SX Molecules with X = H, CH₃, and C(O)CH₃:  Formation of Ketene in Another Decomposition Channel of Sulfenyl Carbonyl Compounds

Abstract

CH 3 C(Ο)SC(O)CH 3 isolated in solid Ar, N 2 , or 5% CO-doped Ar at 15 K and CH 3 C(O)SH and CH 3 C(O)-SCH 3 isolated in solid Ar at 15 K were irradiated with broad-band UV-visible light (200 e λ e 800 nm). On the basis of the IR spectra of the matrixes, hydrogen abstraction from the CH 3 group to give ketene, H 2 CdCdO, with the elimination of HX [X ) SC(O)CH 3 , SH, or SCH 3 ] was identified in each case as the main channel of photodecomposition within the confines of a solid matrix environment. The presence of a CH 3 ligand attached to the carbonyl function thus introduces a third type of elimination reaction for matrixisolated sulfenyl carbonyl compounds of the general type XC(O)SY. Additionally, the conformational properties of the CH 3 C(O)SX molecules have been investigated. In the case of thioacetic acid (X ) H), the matrix experiments indicate that the vapor at ambient temperatures consists of a mixture of the syn and anti forms, with the syn form predominating (ca. 85%). Broad-band UV-visible irradiation then results in interconversion of the conformers prior to decomposition. The identification of the different molecules has been underpinned by the results of ab initio and density functional theory (DFT) calculations.

Methanesulfenyl Fluoride, CH3SF, a Missing Link in the Family of Sulfenyl Halides: Formation and Characterization through the Matrix Photochemistry of Methyl Thiofluoroformate, FC(O)SCH3

“…Comparison with the results of theoretical calculations performed with different methods suggests that these absorptions arise not from the syn (A) but from the anti (B) conformer of FC(O)SCH 3 (in which the C=O bond is oriented anti with respect to the SÀCH 3 bond), which has not been identified previously (Scheme 1). The syn-anti randomization of matrix-isolated sulfenyl carbonyl compounds under UV-visible irradiation appears to be a general feature of this family of compounds, as reported previously, for example, for ClC(O)SCl, [9,10] ClC(O)SBr, [11] FC(O)SCl, [12] FC(O)SBr, [4] CH 3 C(O)SH, [13] FC(O)SNSO, [14] and FC(O)SS-C(O)F. [15] For further evidence, we measured the IR spectrum of perdeuteromethyl thiofluoroformate, FC(O)SCD 3 , both as a vapor (see Supporting Information) and isolated in an Ar matrix. The results correlate closely with those for the normal compound and are also well reproduced by the theoretical calculations.…”

“…The purity of the compound was checked by reference to the IR spectrum of the vapor and to the 1 H, 13 C, and 19 F NMR spectra of the liquid. [8] The perdeuterated compound FC(O)SCD 3 was prepared for the first time by the corre- sponding reaction of ClC(O)SCD 3 [9] with TlF, and also purified by repeated trap-to-trap condensation.…”

Conformational and spectroscopic study of xanthogen ethyl formates, ROC(S)SC(O)OCH2CH3. Isolation of CH3CH2OC(O)SH

“…Table 3 lists the wavenumbers observed in these spectra and also in the IR of an Ar-isolated matrix. The assignment of the bands has been performed with the aid of the predictions of theoretical calculations and also by the comparison with related molecules [14,[16][17][18][19][20]. Although the calculations were performed for the isolated molecule, and therefore ignoring the intermolecular interactions present in the liquid phase, the agreement between the experimental and theoretical spectra is very good.…”

Selenoacetic Acid, CH3C(O)SeH: Preparation, Characterization, and Conformational Properties

“…The formation of these compounds can be explained on the basis of three different photochemical decomposition channels (Scheme 1) analogous to those observed for the irradiation of CH 3 C(O)SH in an argon matrix. [21] In fact, the absorption bands of the ketene and of selenomethanol were observed to decay with longer irradiation times and, starting from CH 3 C(O)SeH, new weak, broad bands appeared near 2984 and 924 cm À1 . A tentative explanation of these bands associates them with the n 1 (2972.5 cm À1 ) and n 4 (916.4 cm À1 ) modes reported very recently for H 2 C = Se trapped in an argon matrix.…”

“…[20] However, its shift to 2110 cm À1 in the IR spectrum of the matrix that contained the precursor CD 3 C(O)SeD and the correlated behavior of several other absorption bands leave little doubt that this band arises from a ketene. [21] By grouping the new bands according to their photochemical behavior, taking the effects of perdeuteration of the precursor into account, and by comparing the bands with reported data, the photoproducts H 2 Se, [22] CH 3 SeH, [15] OCSe, [23] CO, [20] and CH 4 [24] can also be identified. The formation of these compounds can be explained on the basis of three different photochemical decomposition channels (Scheme 1) analogous to those observed for the irradiation of CH 3 C(O)SH in an argon matrix.…”