Layers of glassy solutions of KH12CO3(KD12CO3, K213CO3) and of excess HCl (DCl) dissolved in CH3OH (CH3OD) and in 70 wt.% glycerolâwater have been deposited sequentially at 78 K in the form of droplets, and their reaction in the temperature range 78â300 K studied by FTIR spectroscopy (from 4000 to 400 cmâ1). At ca. 20 K above the glass-transition temperature (Tg) of the solvent, a decrease in viscosity initiated coalescence of the droplets. At ca. 40 K above Tg, protonation of the hydrogen carbonate (carbonate) and formation of H2CO3 occurred in the liquid state. After pumping off the solvent, residual ice and excess HCl, amorphous H212CO3(D212CO3, H213CO3) was isolated, crystallizing at ca. 190â200 K to α-carbonic acid. Assignments for the spectral features of α-H2CO3 and its isotopic forms are given. Base pressure, water content and heating rate lead to varying degrees of disorder in the crystalline phase. The cryogenic method for formation of metastable short-lived intermediates from reaction of non-volatile reactants is discussed. The intermediates can be studied in solution or as amorphous or crystalline solids.
KH12CO3(KD12CO3, K213CO3) 和溶解在 CH3OH (CH3OD) 和 70 wt.%
甘油-
水中的过量 HCl (DCl) 的
玻璃状溶液层在 78 K 下以液滴形式依次沉积,并且它们的反应通过 FTIR 光谱研究的温度范围为 78–300 K(从 4000 到 400 cm–1)。大约在高于溶剂的
玻璃化转变温度 (Tg) 20 K,粘度降低引发液滴聚结。大约在在 Tg 以上 40 K 时,
碳酸氢盐(
碳酸盐)的质子化和 H2CO3 的形成在液态下发生。抽出溶剂、残余冰和过量HCl后,分离出无定形H212CO3(D212CO3,H213CO3),在约100℃结晶。 190–200 K 生成α-
碳酸。给出了α-H2CO3 及其同位素形式的光谱特征的分配。基础压力、含
水量和加热速率导致晶相不同程度的无序。讨论了通过非挥发性反应物反应形成亚稳态短寿命中间体的低温方法。中间体可以在溶液中或作为无定形或结晶固体进行研究。