Matrix Isolation Study of the Conformations and Photochemistry of S-Ethyl Fluorothioformate, FC(O)SCH2CH3

详细信息    查看全文

• 作者：Lucas S. Rodr铆guez Pirani ; Mauricio F. Erben ; Helge Willner ; Rosana M. Romano ; Carlos O. Della V茅dova
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：November 26, 2014
• 年：2014
• 卷：118
• 期：47
• 页码：11193-11203
• 全文大小：480K
• ISSN：1520-5215

文摘

The IR spectra of S-ethyl fluorothioformate, FC(O)SCH₂CH₃, were recorded in the vapor phase and compared with the Raman spectrum in the liquid state. Additional IR spectra of the compound isolated in argon and nitrogen matrices at ca. 12 K were also recorded. The title compound exhibits rich conformational equilibria at room temperature being C₁ the most stable symmetry with a synperiplanar orientation of the carbonyl double bond (C鈺怬) with respect to the S鈥揅(sp³) single bond, while the C鈥揅 bond of the ethyl group presents a gauche orientation with respect to the C鈥揝 single bond. Several bands assigned to a second conformer were also observed in the IR matrix spectra. This second rotamer presents a planar skeleton (C_s point group) retaining the prevalent syn orientation of the FC(O)SCH₂CH₃ molecule with an antiperiplanar orientation of the C鈥揅 bond of the ethyl group with respect to the C鈥揝 bond. The variation of the nozzle temperature before matrix gas deposition gives rise to different conformer ratios. With these data an enthalpy difference of 0.45 kcal mol^鈥? can be calculated between the more stable C₁ and the C_s conformers. A third form, corresponding to the anti-gauche conformer, is also detected when the matrix is exposed to broad-band UV鈥搗isible irradiation. Moreover, the photochemistry of the Ar and N₂ matrix-isolated species is studied. Conformational interconversion is observed at short irradiation times, whereas a decarbonylation process with the concomitant formation of a HC(S)CH₃:HF molecular complex dominates the photochemistry of FC(O)SCH₂CH₃ of longer irradiation times. The new ethyl fluoro sulfide, FSCH₂CH₃, is proposed as an intermediate species.