Gregersen Joshua A, Hao Changtong, Turecek Frantisek
Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, Washington 98195-1700, USA.
J Phys Chem A. 2009 May 21;113(20):5855-64. doi: 10.1021/jp9019987.
In contrast to previously reported electron-super-rich trihydroxy-, triamino- and diaminohydroxymethyl radicals, the title aminodihydroxymethyl radical (1) generates a fraction of metastable species in the form of their deuterium isotopologues. The lifetimes of metastable radicals produced by femtosecond collisional electron transfer to aminodihydroxymethyl cations exceed 4 mus. The main fraction of 1 dissociates by fast loss of a hydroxyl hydrogen atom to form carbamic acid. Loss of an amino hydrogen atom is less facile and becomes <10% competitive at high internal energies or if the main dissociation is slowed down by deuterium isotope effects. RRKM calculations of unimolecular rate constants on a CCSD(T)/aug-cc-pVTZ potential energy surface gave a reasonably good fit for the competitive dissociations of 1 but not for the fraction of nondissociating radicals. The metastable species are attributed to excited electronic states which are predicted to have favorable Franck-Condon factors for being formed by collisional electron transfer.
与先前报道的电子超富的三羟基、三氨基和二氨基羟甲基自由基不同，标题中的氨基二羟甲基自由基（1）以其氘同位素体的形式产生一部分亚稳物种。飞秒碰撞电子转移至氨基二羟甲基阳离子所产生的亚稳自由基的寿命超过4微秒。1的主要部分通过快速失去一个羟基氢原子而解离，形成氨基甲酸。失去一个氨基氢原子的过程较不易发生，在高内能或主要解离因氘同位素效应而减慢时，其竞争性低于10%。在CCSD(T)/aug-cc-pVTZ势能面上对单分子速率常数进行的RRKM计算，对1的竞争性解离给出了合理的良好拟合，但对非解离自由基的部分则不然。亚稳物种归因于激发电子态，预计这些激发电子态因碰撞电子转移而形成时具有有利的弗兰克-康登因子。
