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用D_2~(18)O在Rh-TiO_2/SiO_2催化剂上进行了原位化学截取反应及原位~(18)O同位素交换反应,所得产物中含有氘代乙酸,表明乙烯酮是一种反应中间体;产物中有含~(18)O的乙醇、乙醛、乙酸,表明乙烯酮等C_2含氧前驱中间体与重氧水发生了~(18)O同位素交换反应。按照乙烯酮与水进行同位素交换的模式,只要进行2～3次的交换,就可以解释Katzer等用~(13)C~(16)O/~(12)C~(18)O与H_2反应观察到的产物乙醇的同位素杂组结果,而无须假设乙烯酮异构成能量较高的环氧乙烯然后进行同位素交换,使乙烯酮机理更合理。再次肯定了我们提出的“CO缔合-卡宾-乙烯酮-乙酰基-乙醇(醛)”的机理。
In situ chemical intercalation reaction and isotope exchange reaction in situ with D 2 ~ (18) O on Rh-TiO 2 / SiO 2 catalyst, the obtained product contains deuterated acetic acid, indicating that ketene is a reaction intermediate The products contained ~ 18 O, ethanol, acetaldehyde and acetic acid, indicating that the 18 O isotope exchange reaction occurred between oxygenated precursors such as ketene and oxygenated water. According to the mode of isotope exchange between ketene and water, Katzer et al. Can explain the reaction of ~ (13) C ~ (16) O / ~ (12) C ~ The observed isotopic heterogeneity of the product ethanol results without the need to hypothesize that the ketones are more rationalized by the isomerization of ketene to the more energetic ethylene oxide followed by isotope exchange. Reaffirmed our proposed “CO association - carbene - ketene - acetyl - ethanol (aldehyde)” mechanism.