Transient products of the thermal decay of the colour centres which develop in frozen solutions of polyhalomethanes at 77 K on absorption of near u.-v. light, have been studied by means of u.-v. and visible spectroscopy at low temperatures. Absorption spectra of solvated trihalide ions have been detected, as well as those of weak complexes of molecular halogens with added olefins or with the polyhalomethane itself. The Aââ �X absorption system of CF2 has been observed in viscous solutions of CF2Br2 at low temperature for the first time, and shown to be a product of the thermal decay of the colour centre. Halide ions are produced from all the polyhalomethanes, and could be formed following an electron transfer between neighbouring polyhalomethane molecules. Except for CF2Br2, little or no molecular halogen is released into solution unless it contains dissolved olefins. When molecular halogens are produced, their constituent atoms are both drawn from the same polyhalomethane molecule; they are products of a âmolecularâ reaction rather than association of free halogen atoms.
色心热衰变的瞬态产物,在 77 K 的多卤
甲烷冷冻溶液中吸收近紫外光而形成。光,已通过 u.-v 进行了研究。以及低温下的可见光谱。已检测到溶剂化三卤离子的吸收光谱,以及分子卤素与添加的烯烃或多卤
甲烷本身的弱配合物的吸收光谱。首次在低温下的
CF2Br2粘性溶液中观察到
CF2的A-X吸收体系,并证明其是色心热衰变的产物。卤化物离子由所有多卤
甲烷产生,并且可以在相邻多卤
甲烷分子之间的电子转移后形成。除
CF2Br2 外,除非含有溶解的烯烃,否则很少或没有分子卤素释放到溶液中。当产生分子卤素时,它们的组成原子均来自同一个多卤
甲烷分子;它们是“分子”反应的产物,而不是游离卤素原子缔合的产物。