Chu Li-Kang, Lee Yuan-Pern
Department of Chemistry, National Tsing Hua University, 101, Section 2, Kuang Fu Road, Hsinchu 30013, Taiwan.
J Chem Phys. 2006 Jun 28;124(24):244301. doi: 10.1063/1.2211610.
A step-scan Fourier-transform spectrometer coupled with a 6.4 m multipass absorption cell was employed to detect time-resolved infrared absorption spectra of the reaction intermediate CH3SO2 radical, produced upon irradiation of a flowing gaseous mixture of CH3I and SO2 in CO2 at 248 nm. Two transient bands with origins at 1280 and 1076 cm(-1) were observed and are assigned to the SO2-antisymmetric and SO2-symmetric stretching modes of CH3SO2, respectively. Calculations with density-functional theory (B3LYP/aug-cc-pVTZ and B3P86/aug-cc-pVTZ) predicted the geometry, vibrational, and rotational parameters of CH3SO2 and CH3OSO. Based on predicted rotational parameters, the simulated absorption band of the SO2-antisymmetric stretching mode that is dominated by the b-type rotational structure agrees satisfactorily with experimental results. In addition, a band near 1159 cm(-1) observed at a later period is tentatively attributed to CH3SO2I. The reaction kinetics of CH3 + SO2 --> CH3SO2 and CH3SO2 + I --> CH3SO2I based on the rise and decay of absorption bands of CH3SO2 and CH3SO2I agree satisfactorily with previous reports.
采用一台与6.4米多程吸收池联用的步进扫描傅里叶变换光谱仪，来检测反应中间体CH₃SO₂自由基的时间分辨红外吸收光谱，该自由基是在248纳米波长下，对CO₂中CH₃I和SO₂的流动气态混合物进行辐照时产生的。观察到两个起源于1280和1076厘米⁻¹的瞬态谱带，分别归属于CH₃SO₂的SO₂反对称伸缩模式和SO₂对称伸缩模式。利用密度泛函理论（B3LYP/aug-cc-pVTZ和B3P86/aug-cc-pVTZ）进行的计算预测了CH₃SO₂和CH₃OSO的几何结构、振动和转动参数。基于预测的转动参数，由b型转动结构主导的SO₂反对称伸缩模式的模拟吸收带与实验结果吻合良好。此外，在稍后阶段观察到的1159厘米⁻¹附近的一个谱带初步归属于CH₃SO₂I。基于CH₃SO₂和CH₃SO₂I吸收带的上升和衰减，CH₃ + SO₂ → CH₃SO₂以及CH₃SO₂ + I → CH₃SO₂I的反应动力学与先前的报道吻合良好。
