Duale Khadar, Stace Anthony J
School of Chemistry, The University of Nottingham, University Park, Nottingham, NG7, 2RD, UK.
School of Biology, Chemistry and Forensic Science, Faculty of Science and Engineering, University of Wolverhampton, Wolverhampton, WV1 1SB, UK.
J Am Soc Mass Spectrom. 2019 Sep;30(9):1768-1778. doi: 10.1007/s13361-019-02263-x. Epub 2019 Jul 8.
A comprehensive examination of how the identity of an alcohol molecule can change the behavior of a solvated, alkaline earth dication has been undertaken. The metal dication of Ca has been clustered with a range of different alcohols to form [Ca(ROH)] complexes, where n lies in the range 2-20. Following collisional activation via electron capture from nitrogen gas, complexes for n in the range 2-6 exhibit a switch in reaction product as a function of n. For low values, solvated CaOH is the dominant fragment, but as n increases beyond 4, this is displaced by the appearance of solvated CaOR. A separate study of unimolecular metastable decay by [Ca(ROH)] complexes found evidence of charge separation to form CaOH(ROH) + R. For two isomers of butanol, the n = 3 complexes were found to follow parallel, but different metastable pathways: one leading to the appearance of CaOH and another that resulted in proton abstraction to form ROH. These differences have been attributed to the precursor complexes adopting geometries where one ROH molecule occupies a secondary solvation shell. Comparisons were made with a previous study of magnesium complexes; [Mg(ROH)] show that the difference in second ionization energy Mg (15.09 eV) as opposed to Ca (11.88 eV) influences behavior. A complex between Ca and 1-chloroethanol is shown to favor the formation of CaCl as opposed to CaOH as a unimolecular charge separation product, which is attributed to differences in bond energy in the precursor molecule.
已对酒精分子的身份如何改变溶剂化碱土金属二价阳离子的行为进行了全面研究。钙的金属二价阳离子已与一系列不同的醇聚集形成[Ca(ROH)]络合物，其中n的范围为2至20。通过从氮气中捕获电子进行碰撞活化后，n在2至6范围内的络合物表现出反应产物随n的变化而切换。对于低值，溶剂化的CaOH是主要碎片，但随着n增加超过4，这被溶剂化的CaOR的出现所取代。对[Ca(ROH)]络合物单分子亚稳衰变的另一项研究发现了电荷分离形成CaOH(ROH) + R的证据。对于丁醇的两种异构体，发现n = 3的络合物遵循平行但不同的亚稳途径：一种导致CaOH的出现，另一种导致质子夺取形成ROH。这些差异归因于前体络合物采用的几何结构，其中一个ROH分子占据二级溶剂化壳。与先前对镁络合物的研究进行了比较；[Mg(ROH)]表明，镁（15.09 eV）与钙（11.88 eV）的第二电离能差异影响行为。钙与1-氯乙醇之间的络合物显示，作为单分子电荷分离产物，与CaOH相比，更有利于形成CaCl，这归因于前体分子中键能的差异。
