相转移催化氧化法制备3-甲基-4-硝基苯甲酸

PREPARATION OF 3-METHYL-4-NITROBENZOIC ACID VIA OXIDATION OF 2,4-DIMETHYLNITROBENZENE IN PRESENCE OF PHASE TRANSFER CATALYST

在水、有机相两相体系中,以四丁基溴化铵(TBAB)为相转移催化剂,用KMnO_4选择性氧化2,4-二甲基硝基苯(2,4-DMNB)制备3-甲基-4-硝基苯甲酸。考察了反应条件对产物收率的影响,当反应温度为95℃,反应时间为1h,n(2,4-DMNB):n(KMnO_4):n(TBAB)=1:2．16:0．07时,3-甲基-4-硝基苯甲酸的收率为41%。相同条件下,不加相转移催化剂主要生成4-硝基-1,3-苯二甲酸。从理论上对反应选择性进行了讨论。

2,4-Dimethylnitrobenzene（2,4-DMNB） was oxidized with potassium permanganate to 3- methyl-4-nitrohenzoic acid under heterogeneous conditions in the presence of a phase transfer catalyst,tetrabutyl ammonium bromide（TBAB）. The reaction was carried out at 95 ℃ for 1 h with the ratio of n（2,4-DMNB） ： n（KMnO4） ： n（TBAB） =1： 2.16 ： 0.07 and 3-methyl-4-nitrobenzoic acid was ob- tained in 41% yield. It was found that only 4-nitro-1, 3-benzenedicarboxylic acid was obtained if the reaction was carried out in the absence of the phase transfer catalyst. The factors influencing the above oxidation and the regio selectivity of the oxidation were discussed according to the experimental results and theoretical calculations.