Department of Applied Chemistry, National Chiao Tung University, Hsinchu 30010, Taiwan.
J Chem Phys. 2010 Mar 21;132(11):114303. doi: 10.1063/1.3352315.
A step-scan Fourier-transform infrared spectrometer coupled with a multipass absorption cell was utilized to monitor the transient species produced in gaseous reactions of CH(3)CO and O(2); IR absorption spectra of CH(3)C(O)OO and alpha-lactone were observed. Absorption bands with origins at 1851+/-1, 1372+/-2, 1169+/-6, and 1102+/-3 cm(-1) are attributed to t-CH(3)C(O)OO, and those at 1862+/-3, 1142+/-4, and 1078+/-6 cm(-1) are assigned to c-CH(3)C(O)OO. A weak band near 1960 cm(-1) is assigned to alpha-lactone, cyc-CH(2)C(=O)O, a coproduct of OH. These observed rotational contours agree satisfactorily with simulated bands based on predicted rotational parameters and dipole derivatives, and observed vibrational wavenumbers agree with harmonic vibrational wavenumbers predicted with B3LYP/aug-cc-pVDZ density-functional theory. The observed relative intensities indicate that t-CH(3)C(O)OO is more stable than c-CH(3)C(O)OO by 3+/-2 kJ mol(-1). Based on these observations, the branching ratio for the OH+alpha-lactone channel of the CH(3)CO+O(2) reaction is estimated to be 0.04+/-0.01 under 100 Torr of O(2) at 298 K. A simple kinetic model is employed to account for the decay of CH(3)C(O)OO.
采用分步扫描傅里叶变换红外光谱仪与多通吸收池联用，监测 CH(3)CO 和 O(2)气相反应中生成的瞬态物种；观察到 CH(3)C(O)OO 和 alpha-内酯的红外吸收光谱。起源于 1851+/-1、1372+/-2、1169+/-6 和 1102+/-3 cm(-1) 的吸收带归因于 t-CH(3)C(O)OO，起源于 1862+/-3、1142+/-4 和 1078+/-6 cm(-1) 的吸收带归因于 c-CH(3)C(O)OO。在 1960 cm(-1)附近的一个弱带归因于 alpha-内酯，即 OH 的共产物 cyc-CH(2)C(=O)O。这些观察到的旋转轮廓与基于预测的旋转参数和偶极导数模拟的带线非常吻合，并且观察到的振动波数与用 B3LYP/aug-cc-pVDZ 密度泛函理论预测的谐振动波数一致。观察到的相对强度表明，在 298 K 时，在 100 Torr 的 O(2)下，t-CH(3)C(O)OO 比 c-CH(3)C(O)OO 稳定 3+/-2 kJ mol(-1)。基于这些观察结果，估计在 298 K 时，在 100 Torr 的 O(2)下，CH(3)CO+O(2)反应的 OH+alpha-内酯通道的分支比为 0.04+/-0.01。采用简单的动力学模型来解释 CH(3)C(O)OO 的衰减。
