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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Ether Oxides: A New Class of Stable Ylides? A Theoretical Study of Methanol Oxide and Dimethyl Ether Oxide
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Ether Oxides: A New Class of Stable Ylides? A Theoretical Study of Methanol Oxide and Dimethyl Ether Oxide

机译：醚氧化物：一类新的稳定的叶立德？甲醇氧化物和二甲醚氧化物的理论研究

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The potential energy surfaces of neutral methanol oxide and dimethyl ether oxide and their anion and cation radicals have been calculated at the B_(ECKE)3LYP/6-311++G(d, p) level of theory. Both neutral singlet methanol and dimethyl ether oxides are predicted to correspond to local minima on their potential energy surfaces. natural bonding orbital (NBO) population analysis reveals a distinct ylidic character for these species. Upon increasing methyl substitution, the R_2O~+-O~- ylide structure is stabilized energetically because of the better charge distribution of the formally positive central oxygen atom; thus, the energy differences relative to the R_2O + ~3O exit channel decrease significantly. The barrier for the 1, 2-hydrogen migration in methanol oxide to yield methyl hydroperoxide amounts to only 5 kcal/mol, whereas the methyl shift in dimethyl ether oxide to afford dimethyl peroxide demands >40 kcal/mol and can proceed by retention or inversion of the configuration at the migrating carbon. The kinetic stabilization of the latter is instead determined either by the loss of a methyl radical or by spin crossing to the triplet surface floowed by O atom loss. For this process, the minimal-energy crossing point of the two neutral surfaces was located. The corresponding cation radicals of methanol and dimethyl ether oxide rest in rather deep well, and their geometries are not too different from those of the neutrals. Therefore, neutralization-reionization mass spectrometry may allow generation and identification of the neutral species, provided that the cation-radical precursors can be made. Furthermore, the kinetic stability of neutral dimethyl ether oxide may be sufficient for its detection in matrix isolation experiments.
机译：在B_（ECKE）3LYP / 6-311 ++ G（d，p）的理论水平上计算出了中性甲醇氧化物和二甲醚氧化物及其阴离子和阳离子自由基的势能面。预测中性单线态甲醇和二甲醚氧化物均对应于其势能表面上的局部最小值。自然键合轨道（NBO）种群分析揭示了这些物种的独特的伊德性。随着甲基取代度的增加，R_2O〜+ -O〜-内酯结构由于形式上正中心氧原子的电荷分布更好而得到了能量稳定。因此，相对于R_2O +〜3O出口通道的能量差明显减小。在甲醇氧化物中1,2-氢迁移产生甲基氢过氧化物的势垒仅5 kcal / mol，而在二甲醚氧化物中产生过氧化二甲基的甲基转移要求> 40 kcal / mol，并且可以通过保留或转化来进行迁移碳的构型。后者的动力学稳定性取而代之的是通过甲基基团的损失或通过自旋交叉到因O原子损失而流动的三重态表面来确定。在此过程中，找到了两个中性表面的最小能量交叉点。甲醇和二甲醚氧化物的相应阳离子自由基位于相当深的井中，并且它们的几何形状与中性粒子没有太大差异。因此，中和-去离子质谱可以允许产生和鉴定中性物质，条件是可以制备阳离子自由基前体。此外，中性二甲醚氧化物的动力学稳定性可能足以在基质分离实验中对其进行检测。

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