Synthesis And Characterization Of 2-Methylallylidene Diacetate

2-Methylallylidene diacetate(DMA) is a very important organic intermediate infine chemical industry and can be widely used in the synthesis of perfumes,pharmaceutical intermediates and organic intermediates. Also it can be used as asynthon of inserting the aldo group. Therefore, the synthesis of 2-methylallylidenediacetate is of great importance.2-Methylallylidene diacetate was synthesised by the reaction of MAL with aceticanhydride under catalysis of strong acidic cation-exchanger resin. The effects ofstirring rate, amount of the catalyst, molar ratio of raw materials, reaction temperatureand reaction time on the reaction were observed, the optimum conditions were:stirring rate 200rpm, n((CH3CO)2O) :n(MAL)=1.2:1.0,amount of strong acidiccation-exchanger resin D072 2.0g(per molar MAL), reaction temperature -10℃andreaction time 5h. Under these conditions, the conversion of MAL was 95.5%, theselectivity and yield of DMA were 95.7% and 91.4ï¼…. The structure of product wasidentified by IR,GC-MS and 1HNMR.The kinetic study was made on the synthesis of 2-methylallylidene diacetate withMAL and acetic anhydride using strong acidic cation-exchanger resin as the catalystin a batch mode reactor, under the conditions that internal and external diffusionscould be eliminated. The kinetic constants such as the pre-exponential factor andactivation energy were measured: Ea⁺＝-3.657 kJ/mol, k0+＝0.0708 L/mol ?h; Ea-＝21.60kJ/mol,k0-＝4.373×10² h^-1.Thus, the kinetic equation could represent thereaction rate expression.The mechanism of the reaction of MAL and acetic anhydride was discussed inthis paper and was explained in brief according to the kinetic dates, the regionselectivity of MAL was 1,2-additions.