Kéki Sándor, Nagy Lajos, Török János, Tóth Katalin, Lévai Albert, Zsuga Miklós
Department of Applied Chemistry, University of Debrecen, Egyetem tér 1, H-4010 Debrecen, Hungary.
Rapid Commun Mass Spectrom. 2007;21(11):1799-808. doi: 10.1002/rcm.3029.
The pathways of the (M+H) ions generated from electrosprayed solutions of nine 1,3,5-trisubstituted 2-pyrazoline derivatives were studied using energy-variable collision-induced dissociation (CID) and pseudo-MS(3) (in-source CID combined with MS/MS) methods. It was shown that under CID conditions several structurally important product ions such as the 2,4-substituted azete and 1,2-substituted aziridine ions were formed. The compositions of the product ions were unambiguously supported by accurate mass measurement (mass accuracy was within +/- 8 ppm). The fragmentation pathways of 1,3,5-trisubstituted 2-pyrazolines were established by means of pseudo-MS(3). It was found that a substituent at the N-1 position greatly affects the fragmentation pathways of the 2-pyrazoline derivatives. The 1-acetyl- and 1-propionyl-2-pyrazoline derivatives dissociate mainly through formation of a pyrazolium cation, while in the case of 1-phenyl-2-pyrazoline derivatives product ions arising from the consecutive fragmentation of 2,4-substituted azete and 1,2-substituted aziridine ions dominate. Another interesting finding is the formation of a radical cation from the 2,4-substituted azete by loss of a methyl radical. The fragmentation yield as a function of the collision energy for each of the 1,3,5-trisubstituted 2-pyrazolines was determined. Based on the fragmentation yield versus collision energy curves the relative fragmentation stabilities for the 1,3,5-trisubstituted 2-pyrazoline derivatives were also evaluated.
采用能量可变的碰撞诱导解离（CID）和伪MS(3)（源内CID与MS/MS联用）方法，研究了9种1,3,5-三取代2-吡唑啉衍生物的电喷雾溶液产生的（M+H）离子的裂解途径。结果表明，在CID条件下，形成了几种结构上重要的产物离子，如2,4-二取代氮杂环丁烷离子和1,2-二取代氮丙啶离子。通过精确质量测量（质量准确度在±8 ppm以内）明确支持了产物离子的组成。借助伪MS(3)确定了1,3,5-三取代2-吡唑啉的裂解途径。发现N-1位的取代基对2-吡唑啉衍生物的裂解途径有很大影响。1-乙酰基-和1-丙酰基-2-吡唑啉衍生物主要通过形成吡唑鎓阳离子解离，而对于1-苯基-2-吡唑啉衍生物，由2,4-二取代氮杂环丁烷和1,2-二取代氮丙啶离子连续裂解产生的产物离子占主导。另一个有趣的发现是2,4-二取代氮杂环丁烷通过失去一个甲基自由基形成一个自由基阳离子。测定了每种1,3,5-三取代2-吡唑啉的裂解产率与碰撞能量的函数关系。基于裂解产率与碰撞能量曲线，还评估了1,3,5-三取代2-吡唑啉衍生物的相对裂解稳定性。
