Photodissociation of Thioacetic Acid Using Time-resolved Fourier-transform Infrared Spectroscopy:Carbon Monoxide, Carbonyl Sulfide, Methyl Mercaptan, and Methane Elimination via Argon Collision-Induced Internal Conversion Process

• Main Authors: En-Lan Hu, 胡恩蘭
• Other Authors: 林金全
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/27231089879315894556

碩士 === 國立臺灣大學 === 化學研究所 === 100 === Photodissociation dynamics of thioacetic acid at 248nm is studied by detecting photofragments with step-scan time-resolved Fourier-transform infrared emission spectroscopy. We can observe CO and OCS fundamental vibrational emission spectra in the mid-infrared range from 1850 cm-1 to 2200 cm-1. CH3SH, CH4, and H2S are also detected in the range of 2400 - 3300 cm-1; however, we proposed the signals are mainly contributed by CH3SH and CH4, due to the poor emission intensity of H2S. Information of internal energy distribution in photofragments can be obtained via spectral analysis of experimental data. Assignments of the CO spectra indicate that vibrational level is populated up to ν=3 and rotational level J up to J=35. In this study, the CO fragments are directly confirmed by high resolution rovibrational spectral observation. On the other hand, the CH2 product can only be indirectly confirmed by the reaction with O2 to form CO2. We found that the addition of Ar or O2 quenching gas enhance the collision-induced internal conversion process in the photodissociation of CH3COSH. In previous theoretical work, there are three predominant dissociation channels. The first pathway leads to the products of CO and CH3SH through a three-membered ring intermediate. The second pathway leads to OCS and CH4 products. The third pathway yields ketene and H2S, and ketene decomposes further into CO and CH2. The photodissociation study of thioacetic acid in gas phase allows us to gain further understanding of chalcogen substituted carboxylic acid.