McCarley T D, Brodbelt J
Department of Chemistry and Biochemistry, University of Texas, Austin 78712-1167.
Anal Chem. 1993 Sep 1;65(17):2380-8. doi: 10.1021/ac00065a035.
The ion-molecule reactions of various 1,4-benzodiazepines and dimethyl ether ions were studied with a quadrupole ion trap mass spectrometer. The methoxymethylene ions of dimethyl ether selectively react with 3-hydroxy-1,4-benzodiazepines (temazepam, oxazepam) to form (M+13)+ adducts by methylene substitution, and they react with 1,4-benzodiazepines that do not have hydroxyl substituents (diazepam, nordiazepam, nitrazepam) to form (M+15)+ adduct by a simple methyl cation transfer. These adducts are formed by elimination of methanol or formaldehyde, respectively, from (M+CH2OCH3)+ precursor ions. Ion-molecule reactions of model compounds with dimethyl ether ions suggest that the reactive site in the formation of (M+15)+ adducts is the imine functional group of the 1,4-benzodiazepines, while the reactive site for formation of (M+13)+ adducts involves a functional group interaction between the hydroxyl and carbonyl functional groups. Fragmentation induced by chemical ionization and collisionally activated dissociation provides further structural information for the differentiation of 1,4-benzodiazepines. Also, the gas-phase basicities of diazepam and temazepam have been estimated by bracketing techniques to be between 220.7 and 222.2 kcal/mol.
利用四极杆离子阱质谱仪研究了各种1,4 - 苯二氮䓬类化合物与二甲醚离子的离子 - 分子反应。二甲醚的甲氧基亚甲基离子选择性地与3 - 羟基 - 1,4 - 苯二氮䓬类化合物（替马西泮、奥沙西泮）反应，通过亚甲基取代形成(M + 13)+加合物，并且它们与没有羟基取代基的1,4 - 苯二氮䓬类化合物（地西泮、去甲西泮、硝西泮）反应，通过简单的甲基阳离子转移形成(M + 15)+加合物。这些加合物分别由(M + CH₂OCH₃)+前体离子消除甲醇或甲醛形成。模型化合物与二甲醚离子的离子 - 分子反应表明，(M + 15)+加合物形成中的反应位点是1,4 - 苯二氮䓬类化合物的亚胺官能团，而(M + 13)+加合物形成的反应位点涉及羟基和羰基官能团之间的官能团相互作用。化学电离和碰撞诱导解离引起的碎片化提供了用于区分1,4 - 苯二氮䓬类化合物的进一步结构信息。此外，通过括值技术估计地西泮和替马西泮的气相碱度在220.7至222.2千卡/摩尔之间。
