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在微型高压反应釜中 (12 0ml) ,考察了酸催化三聚甲醛和甲酸甲酯制备羟基乙酸甲酯的偶联反应 ,并对酸催化剂中H+的作用进行了研究。在该偶联反应体系中 ,H+浓度直接影响着甲酸甲酯的分解速率和羟基乙酸甲酯的收率。甲酸甲酯在偶联反应中是以CO和CH3OH的载体形式而存在。在H+的催化作用下 ,该偶联反应机理可分三步完成 :(a)H+的催化作用促使甲酸甲酯分解产生CO和CH3OH ,三聚甲醛分解形成羟甲基正离子和甲氧基甲基正离子HOC H2 ;(b)羟甲基正离子CH3OC H2 和甲氧基甲基正离子与CO进行羰化作用形成产物中间体或过渡态化合物 ;(c)中间体或过渡态化合物的甲醇醇解形成羟基乙酸甲酯、甲氧基乙酸甲酯和乙醇酸。
In a miniature autoclave (120ml), the coupling reaction between acid catalyzed trioxane and methyl formate was investigated. The effect of H + in acid catalyst was also studied. In the coupled reaction system, the H + concentration directly affects the decomposition rate of methyl formate and the yield of methyl glycolate. Methyl formate is present as a carrier of CO and CH3OH in the coupling reaction. Under the catalysis of H +, the coupling reaction mechanism can be completed in three steps: (a) the catalysis of H + causes the methyl formate to decompose to produce CO and CH3OH, and the paraformaldehyde decomposes to form methylolmelamine and methoxymethyl Base positive ion HOC H2; (b) hydrocomethylation of the methylol cations CH3OC H2 and methoxymethyl cations with CO to form the product intermediate or transition state compound; (c) the intermediate or transition state compound in methanol Alcoholysis forms methyl hydroxy acetate, methyl methoxy acetate and glycolic acid.