Florián Jan, Gao Lan, Zhukhovskyy Vladimir, Macmillan Denise K, Chiarelli M Paul
Department of Chemistry, Loyola University, Chicago, Illinois 60626, USA.
J Am Soc Mass Spectrom. 2007 May;18(5):835-41. doi: 10.1016/j.jasms.2007.01.009. Epub 2007 Feb 20.
The fragment ion formation characteristics of the radical anions generated from hexahydro-1,3,5-trinitrotriazine (RDX) and its three nitroso metabolites were studied using GC/MS with negative chemical ionization (NCI) to understand the fragmentation mechanisms responsible for the formation of the most abundant ions observed in their NCI mass spectra. Ab initio and density functional theory calculations were used to calculate relative free energies for different fragment ion structures suggested by the m/z values of the most abundant ions observed in the NCI mass spectra. The NCI mass spectra of the four nitramines are dominated by ions formed by the cleavage of nitrogen-nitrogen and carbon-nitrogen bonds in the atrazine ring. The most abundant anions in the NCI mass spectra of these nitramines have the general formulas C(2)H(4)N(3)O (m/z 86) and C(2)H(4)N(3)O(2) (m/z 102). The analyses of isotope-labeled standards indicate that these two ions are formed by neutral losses that include two exocylic nitrogens and one atrazine ring nitrogen. Our calculations and observations of the nitramine mass spectra suggest that the m/z 86 and m/z 102 ions are formed from either the (M--NO)(-) or (M--NO(2))(-) fragment anions by a single fragmentation reaction producing neutral losses of CH(2)N(2)O or CH(2)N(2)O(2) rather than a set of sequential reactions involving neutral losses of HNO(2) or HNO and HCN.
使用带有负化学电离（NCI）的气相色谱/质谱联用仪（GC/MS）研究了六氢-1,3,5-三硝基三嗪（RDX）及其三种亚硝基代谢物产生的自由基阴离子的碎片离子形成特征，以了解其NCI质谱中观察到的最丰富离子形成的碎裂机制。采用从头算和密度泛函理论计算来计算由NCI质谱中观察到的最丰富离子的m/z值所暗示的不同碎片离子结构的相对自由能。这四种硝胺的NCI质谱主要由阿特拉津环中氮-氮键和碳-氮键断裂形成的离子主导。这些硝胺的NCI质谱中最丰富的阴离子具有通式C(2)H(4)N(3)O（m/z 86）和C(2)H(4)N(3)O(2)（m/z 102）。对同位素标记标准物的分析表明，这两种离子是由包括两个环外氮和一个阿特拉津环氮的中性损失形成的。我们对硝胺质谱的计算和观察表明，m/z 86和m/z 102离子是由（M--NO）（-）或（M--NO(2)）（-）碎片阴离子通过单次碎裂反应形成的，该反应产生CH(2)N(2)O或CH(2)N(2)O(2)的中性损失，而不是涉及HNO(2)或HNO和HCN中性损失的一系列连续反应。
