相转移催化氧化法制备3-甲基-4-硝基苯甲酸

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。

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

2,4-Dimethylnitrobenzene (2,4-DMNB) was oxidized with potassium permanganate to 3- methyl-4-nitrobenzoic 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(KMnO_4):n(TBAB)=1:2.16:0.07 and 3-methyl-4-nitrobenzoie 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 a- bove oxidation and the regio selectivity of the oxidation were discussed according to the experimental results and theoretical calculations.