Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221, United States.
J Phys Chem A. 2010 Dec 9;114(48):12667-74. doi: 10.1021/jp108457w. Epub 2010 Nov 15.
The matrix isolation technique, combined with infrared spectroscopy and twin jet codeposition, has been used to characterize intermediates formed during the ozonolysis of 2,3-dimethyl-2-butene (DMB). Absorptions of early intermediates in the twin jet experiments grew up to 200% upon annealing to 35 K. A number of these absorptions have been assigned to the elusive Criegee intermediate (CI) and secondary ozonide (SOZ) of DMB, transient species not previously observed for this system. Also observed was the primary ozonide (POZ), in agreement with earlier studies. The wavelength dependence of the photodestruction of these product bands was explored with irradiation from λ ≥ 220 to ≥580 nm. Merged jet (flow reactor) experiments generated "late" stable oxidation products of DMB. A recently developed concentric jet method was also utilized to increase yields and monitor the concentration of intermediates and products formed at different times by varying the length of mixing distance (d = 0 to -11 cm) before reaching the cold cell for spectroscopic detection. Identification of intermediates formed during the ozonolysis of DMB was further supported by (18)O and scrambled (16,18)O isotopic labeling experiments as well as theoretical density functional calculations at the B3LYP/6-311++G(d,2p) level.
采用矩阵隔离技术，结合红外光谱和双射流共沉积技术，对 2,3-二甲基-2-丁烯（DMB）臭氧化过程中形成的中间体进行了表征。在双射流实验中，早期中间体的吸收在退火至 35 K 时增加了 200%。其中一些吸收已被分配给难以捉摸的 Criegee 中间体（CI）和 DMB 的次级臭氧化物（SOZ），这是该体系以前未观察到的瞬态物质。还观察到了初级臭氧化物（POZ），这与早期的研究结果一致。用 λ≥220 至≥580nm 的光辐照，研究了这些产物带的光解波长依赖性。合并射流（流动反应器）实验生成了 DMB 的“晚期”稳定氧化产物。还利用最近开发的同心射流方法来增加产率，并通过改变混合距离（d=0 至-11cm）来监测在不同时间形成的中间体和产物的浓度，混合距离是在到达冷腔进行光谱检测之前的距离。通过（18）O 和混乱（16,18）O 同位素标记实验以及 B3LYP/6-311++G(d,2p)水平的理论密度泛函计算，进一步支持了 DMB 臭氧化过程中形成的中间体的鉴定。
