Gares Katie L, Bykov Sergei V, Asher Sanford A
Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States.
J Phys Chem A. 2017 Oct 19;121(41):7889-7894. doi: 10.1021/acs.jpca.7b07588. Epub 2017 Oct 9.
Ultraviolet resonance Raman spectroscopy (UVRR) is being developed for standoff trace explosives detection. To accomplish this, it is important to develop a deep understanding of the accompanying UV excited photochemistry of explosives, as well as the impact of reactions on the resulting photoproducts. In the work here we used 229 nm excited UVRR spectroscopy to monitor the photochemistry of pentaerythritol tetranitrate (PETN) in acetonitrile. We find that solutions of PETN in CDCN photodegrade with a quantum yield of 0.08 ± 0.02, as measured by high performance liquid chromatography (HPLC). The initial step in the 229 nm UV photolysis of PETN in CDCN is cleavage of an O-NO bond to form NO. The accompanying photoproduct is pentaerythritol trinitrate (PETriN), (CHONO)CCHOH formed by photolysis of a single O-NO. The resulting UVRR spectra show a dominant photoproduct band at ∼1308 cm, which derives from the symmetric stretch of dissolved NO. This photoproduct NO is hydrolyzed by trace amounts of water, which downshifts this 1308 cm NO Raman band due to the formation of molecular HNO. The dissociation of HNO to NO in the presence of additional water results in an intense NO- symmetric stretching UVRR band at 1044 cm.
紫外共振拉曼光谱（UVRR）正被用于远距离痕量炸药检测。要实现这一目标，深入了解炸药伴随的紫外激发光化学过程以及反应对生成的光产物的影响非常重要。在本研究中，我们使用229nm激发的UVRR光谱监测了季戊四醇四硝酸酯（PETN）在乙腈中的光化学过程。我们发现，通过高效液相色谱（HPLC）测量，PETN在CDCN中的溶液光降解的量子产率为0.08±0.02。PETN在CDCN中229nm紫外光解的初始步骤是O-NO键的断裂形成NO。伴随的光产物是季戊四醇三硝酸酯（PETriN），即(CHONO)CCHOH，它是由单个O-NO光解形成的。所得的UVRR光谱在~1308cm处显示出一个主要的光产物带，它源自溶解的NO的对称伸缩振动。这种光产物NO会被痕量的水水解，由于分子HNO的形成，这会使1308cm处的NO拉曼带向低波数移动。在有额外水存在的情况下，HNO分解为NO会导致在1044cm处出现一个强烈的NO对称伸缩UVRR带。
