2,4-二甲基苯甲酸的合成

Synthesis of 2,4 -Dimethyl Benzoic Acid

以间二甲苯和氯乙酰氯为主要原料,经Friedel-crafts酰基化反应、氯仿反应及酸化等过程,合成了目的产物,研究了反应过程的影响因素,确定了反应条件。在酰基化反应中,n(C_8H_(11)):n(ClCH_2COCl):n(Fe_2O_3)=1:(1.2～1.3):0.001,反应温度100℃,反应时间4h,产率为88％～91％。在α-氢卤代及氯仿反应的过程中,通过分次补加40％(w_(NaOH))氢氧化钠水溶液以保证反应的发生并提高产率,总收率为80％。产品经红外、核磁鉴定为2,4-二甲基苯甲酸。

2,4-dimethyl benzoic acid was synthesized from mesitylene and chloro-acetyl chloride by Friedel-Crafts acylation,α-hydrogen halogenation, haloform reaction and acidification. Factors influencing these reactions were studied. Yield of acylation was 88%-91% when n(C8H11):n (ClCH2COCl).n(Fe2O3) = 1: (1.2-1. 3): 0.001. And the total yield was 80% when the concentration of alkali solution was strong enough to accelerate a-hydrogen halogenation and haloform reaction. The title compound was identified by IR and H NMR.