Yin H, Hachey D L, Porter N A
Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, USA.
J Am Soc Mass Spectrom. 2001 Apr;12(4):449-55. doi: 10.1016/S1044-0305(01)00205-7.
Organic peroxides have significance in organic synthesis and biological processes. Characterization of these compounds with weak O-O bonds is sometimes difficult due to their thermal instability and sensitivity to acid or base. Coordination of diacyl peroxides with AgBF4 provides a means for analysis of these compounds by coordination ionspray tandem mass spectrometry (CIS-MS/MS). Precursor ion (Q1) scans of acetyl benzoyl peroxide give two Ag+ adducts, [M + Ag + solvent]+ and [M + Ag + M]+. These silver ion adducts can be selectively dissociated (CID) to give unique structural information about the analyte. Decomposition of the [M + Ag + solvent]+ adduct generates fragmentation products due to apparent homolytic cleavage of the O-O bond followed by decarboxylation of the resultant radicals. The bis-diacylperoxide complex, [M + Ag + M]+ gives CID pathways that involve homolysis of the (O-O bond and free radical cross-coupling of the two diacyl peroxides coordinated to the silver ion, i.e. formation of dibenzoyl peroxide, phenyl benzoate, and biphenyl from acetyl benzoyl peroxide. The observation of free radical CID modes is uncommon in mass spectrometry but these pathways are consistent with well-known solution and gas phase processes for peroxide compounds. The proposed fragmentation pathways have been supported by experiments with (18)O and deuterated substrates. This technique can be applied to analyze diacyl peroxides with different substituents as well.
有机过氧化物在有机合成和生物过程中具有重要意义。由于这些具有弱O - O键的化合物热不稳定且对酸或碱敏感，对其进行表征有时会很困难。二酰基过氧化物与AgBF4的配位作用为通过配位离子喷雾串联质谱（CIS - MS/MS）分析这些化合物提供了一种方法。乙酰苯甲酰过氧化物的前体离子（Q1）扫描产生两种Ag +加合物，即[M + Ag +溶剂]+和[M + Ag + M]+。这些银离子加合物可以被选择性地解离（CID），以给出有关分析物的独特结构信息。[M + Ag +溶剂]+加合物的分解由于O - O键明显的均裂，随后是所得自由基的脱羧反应，产生了碎片产物。双二酰基过氧化物配合物[M + Ag + M]+给出的CID途径涉及（O - O键的均裂以及与银离子配位的两种二酰基过氧化物的自由基交叉偶联，即从乙酰苯甲酰过氧化物形成二苯甲酰过氧化物、苯甲酸苯酯和联苯。自由基CID模式在质谱分析中并不常见，但这些途径与过氧化物化合物众所周知的溶液和气相过程一致。所提出的碎片途径已得到用（18）O和氘代底物进行的实验的支持。该技术也可应用于分析具有不同取代基的二酰基过氧化物。
