Petersen B A, Vouros P, Parker J M, Karger B L
J Forensic Sci. 1976 Apr;21(2):279-90.
On the basis of the data presented above the following conclusions may be drawn. 1. The molecular ion peaks of most of the compounds examined are relatively weak but usually easily discernible to permit molecular weight determination. 2. The mass spectra of benzilate esters exhibit a relatively intense peak at m/e 183, and monitoring of this ion can serve as a means for preliminary screening for the presence of this type of a system. 3. Related esters exhibit a similar type of fragmentation resulting in a fragment ion analogous to m/e 183 but shifted by the appropriate number of mass units according to the substituents present. 4. Cleavage of the piperidine ring-ester oxygen bond in 3 and 4-substituted isomers is followed by selective losses of hydrogen radicals to produce ions of type e, f, and g as indicated above. It is significant that in a related piperidine ring system (methylphenidate) substituted in the 2 position, the same type of cleavage results in no further hydrogen losses [16] because of charge stabilization from the ring nitrogen (ion j, Fig. 17) [17]. In other words, the tendency to form a conjugated ion following initial bond cleavage can serve as a means for identifying the position of substitution on the ring and for distinguishing positional isomers.
基于上述数据，可得出以下结论。1. 所检测的大多数化合物的分子离子峰相对较弱，但通常易于辨别以确定分子量。2. 二苯乙醇酸酯的质谱在m/e 183处呈现相对较强的峰，监测该离子可作为初步筛选此类体系存在的一种方法。3. 相关酯类表现出类似的裂解类型，产生类似于m/e 183的碎片离子，但根据存在的取代基按适当的质量单位数发生位移。4. 3和4位取代异构体中哌啶环 - 酯氧键的裂解之后，如上文所示，会选择性地失去氢自由基以产生e、f和g型离子。值得注意的是，在2位取代的相关哌啶环体系（哌醋甲酯）中，由于环氮的电荷稳定作用（离子j，图17），相同类型的裂解不会导致进一步的氢损失[16][17]。换句话说，初始键裂解后形成共轭离子的倾向可作为确定环上取代位置和区分位置异构体的一种方法。
