Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907, USA.
J Am Soc Mass Spectrom. 2012 Jan;23(1):12-22. doi: 10.1007/s13361-011-0249-y. Epub 2011 Oct 15.
A mass spectrometric method has been delineated for the identification of the epoxide functionalities in unknown monofunctional analytes. This method utilizes gas-phase ion/molecule reactions of protonated analytes with neutral trimethyl borate (TMB) followed by collision-activated dissociation (CAD) in an ion trapping mass spectrometer (tested for a Fourier-transform ion cyclotron resonance and a linear quadrupole ion trap). The ion/molecule reaction involves proton transfer from the protonated analyte to TMB, followed by addition of the analyte to TMB and elimination of methanol. Based on literature, this reaction allows the general identification of oxygen-containing analytes. Vinyl and phenyl epoxides can be differentiated from other oxygen-containing analytes, including other epoxides, based on the loss of a second methanol molecule upon CAD of the addition/methanol elimination product. The only other analytes found to undergo this elimination are some amides but they also lose O = B-R (R = group bound to carbonyl), which allows their identification. On the other hand, other epoxides can be differentiated from vinyl and phenyl epoxides and from other monofunctional analytes based on the loss of (CH(3)O)(2)BOH or formation of protonated (CH(3)O)(2)BOH upon CAD of the addition/methanol elimination product. For propylene oxide and 2,3-dimethyloxirane, the (CH(3)O)(2)BOH fragment is more basic than the hydrocarbon fragment, and the diagnostic ion (CH(3)O)(2)BOH (2) (+) is formed. These reactions involve opening of the epoxide ring. The only other analytes found to undergo (CH(3)O)(2)BOH elimination are carboxylic acids, but they can be differentiated from the rest based on several published ion/molecule reaction methods. Similar results were obtained in the Fourier-transform ion cyclotron resonance and linear quadrupole ion trap mass spectrometer.
已经提出了一种质谱方法来鉴定未知单官能分析物中的环氧化物官能团。该方法利用质子化分析物与中性三甲基硼酸（TMB）的气相离子/分子反应，然后在离子阱质谱仪中进行碰撞激活解离（CAD）（经过傅里叶变换离子回旋共振和线性四极离子阱测试）。离子/分子反应涉及质子从质子化分析物转移到 TMB，然后分析物与 TMB 加成并消除甲醇。根据文献，该反应允许一般鉴定含氧分析物。乙烯基和苯基环氧化物可以与其他含氧分析物（包括其他环氧化物）区分开来，这是基于 CAD 后加成/甲醇消除产物失去第二个甲醇分子。发现只有其他酰胺也会经历这种消除，但它们也会失去 O = B-R（R = 与羰基结合的基团），这允许对它们进行鉴定。另一方面，其他环氧化物可以根据 CAD 后加成/甲醇消除产物失去（CH(3)O)(2)BOH 或形成质子化（CH(3)O)(2)BOH 来区分乙烯基和苯基环氧化物以及其他单官能分析物。对于环氧丙烷和 2,3-二甲氧基环氧化合物，（CH(3)O)(2)BOH 片段比烃片段更碱性，形成诊断离子（CH(3)O)(2)BOH(2)(+)。这些反应涉及环氧化物环的开环。发现只有其他分析物经历（CH(3)O)(2)BOH 消除，是羧酸，但可以根据几种已发表的离子/分子反应方法将它们与其他物质区分开来。在傅里叶变换离子回旋共振和线性四极离子阱质谱仪中也得到了类似的结果。
