Origin of [M + H]+ ions in electron impact mass spectra of tertiary nitrosonitriles
作者:Karol Grela、Leszek Konopski
DOI:10.1002/jms.1190301009
日期:1995.10
The presence of [M + H]+ ions was observed in the electron impact mass spectra of the series of dimers of aliphatic tertiary β-, γ- and δ-nitrosonitriles. Neither M+· nor [M + H]+ ions are observed in the spectra of α-nitrosonitriles or after introduction of voluminous substituents into the molecule, so the geometric factor is very important. It was found that this effect was probably due to the rearrangement of the hydrogen atom in the fragmentation pattern of the dimer molecular ions 2M+· of β- and δ-nitrosonitriles. Aliphatic nitrosocompounds exist even in the gas phase in equilibrium with their dimers. The existence of dimers was confirmed by the presence of the [2M + H]+· ion in the liquid secondary ion mass spectrum of a γ-nitrosonitrile. Using deuterium labelling, as distinct to the nitrosoketones and esters, it was unexpectedly found that the origin of hydrogen in the [M + H]+ ions was the methyl groups in the position vicinal to the tertiary nitroso group (CH3)2C(NO)R.
在脂肪族三级 β-、γ- 和 δ-亚硝腈二聚体系列的电子碰撞质谱中观察到了 [M + H]+ 离子的存在。在 α-亚硝基腈的光谱中或在分子中引入大量取代基后,均未观察到 M+- 或 [M + H]+ 离子,因此几何因素非常重要。研究发现,这种影响可能是由于在 β- 和 δ-亚硝腈的二聚分子离子 2M+- 的碎片模式中氢原子发生了重排。脂肪族亚硝基化合物甚至在气相中与其二聚体处于平衡状态。γ-亚硝腈的液态二次离子质谱中出现的 [2M + H]+- 离子证实了二聚体的存在。与亚硝基酮类和酯类不同,利用氘标记法意外发现,[M + H]+ 离子中氢的来源是与三级亚硝基基团 (CH3)2C(NO)R 邻接位置上的甲基。