Abstract: 2-methyl-1,4-naphthoquinone (2-MNQ) is an important intermediate of K vitamins, which is widely used in medicine, pesticides, feed additives and other fields. However, this vitamin does not exist in nature, and artificial synthesis is the only way to produce 2-MNQ. In industry, vitamin K3 is prepared using 2-methylnaphthalene (2-MN) as raw material and chromic anhydride as an oxidant. This process produces a large amount of waste residue and wastewater containing chromium, causing irreversible pollution to the environment,and trace amounts of chromium in the product pose a threat to human health. Therefore, a new type of the green oxidation process was used for hydrogen peroxide oxidation. The process used 2-methylnaphthalene (2-MN) as raw material, (NH4)2S2O8 as initiator to prepare peroxygen with 30% H2O2 and glacial acetic acid under the catalysis of sulfuric acid. Acetic acid was added dropwise to the reaction solution to synthesize 2-methyl-1,4-naphthoquinone (2-MNQ) by oxidation, and its structure was characterized by ICIR, GC-MS, and LCMS, and the oxidation reaction mechanism and the type and content of by-products were verified. The main impurities were isomer 6-methyl-1,4-naphthoquinone and its by-products phthalic anhydride and 4-methylphthalic anhydride produced by excessive oxidation. The effects of catalyst, reaction temperature, reaction time, dosage of oxidizer and initiator on the yield and conversion of 2-MNQ were investigated. The conversion rate and yield of 2-MNQ were determined by HPLC (external standard method). The optimum reaction conditions were reaction temperature of 65℃, reaction time of 5 h, n(H2O2):n(2-MN)=26:1. The conversion rate of 2-methylnaphthalene was 99%, and the product yield was 34%. The innovation point of this work was to verify the reaction mechanism and the intermediate process in detail using the original external infrared, that was, the raw material 2-methylnaphthalene was oxidized by peracetic acid, the epoxidation reaction generated the intermediate, and then rearranged to generate 2-methylhydroxyquinone, and the oxidation continued to generate the target product 2-methyl-1,4-naphthalene quinone. The process has the characteristics of environment friendly, simple technology, mild operating conditions and easy availability of raw materials.The process uses 2-methylnaphthalene (2-MN) as raw material, (NH4)2S2O8 as initiator to prepare peroxygen with 30% H2O2 and glacial acetic acid under the catalysis of sulfuric acid. Acetic acid was added dropwise to the reaction solution to synthesize 2-methyl-1,4-naphthoquinone (2-MNQ) by oxidation, and its structure was characterized by ICIR, GC-MS, and LCMS, and the oxidation reaction mechanism and the type and content of by-products were verified. The main impurities were isomer 6-methyl-1,4-naphthoquinone and its by-products phthalic anhydride and 4-methylphthalic anhydride produced by excessive oxidation. The effects of catalyst, reaction temperature, reaction time, dosage of oxidizer and initiator on the yield and conversion of 2-MNQ were investigated. The conversion rate and yield of 2-MNQ were determined by HPLC (external standard method). The optimum reaction conditions were obtained reaction temperature 65℃, reaction time 5h, n(CH3COOOH):n(2-MN) = 26:1. The conversion rate of 2-methylnaphthalene was 98%, and the product yield was 35%. The innovation point of this paper is to verify the reaction mechanism and the intermediate process in detail using the original external infrared, that is, the raw material 2-methylnaphthalene is oxidized by oxyacetic acid, the epoxidation reaction generates the intermediate, and then the rearranges to generates 2-methylhydroxyquinone, and the oxidation continues to generate the target product 2-methyl-1, 4-naphthalene quinone. The process has the characteristics of environment friendly, simple technology, mild operating conditions and easy availability of raw materials.

Key words: 2-methylnaphthalene, 2-methyl-1,4-naphthoquinone, oxidation reaction, green synthesis

摘要： 2-甲基-1,4-萘醌(2-MNQ)是K族维生素的重要中间体，广泛应用于医药、农药、饲料添加剂等领域。本工作以2-甲基萘(2-MN)为原料，(NH4)2S2O8为引发剂，用30% H2O2与冰醋酸在硫酸催化下制备过氧乙酸并滴加至反应液中，氧化合成2-甲基-1,4-萘醌(2-MNQ)，通过ICIR, GC-MS, LCMS对其结构进行表征，并验证氧化反应机理及中间产物。考察了催化剂、反应温度、反应时间、氧化剂与引发剂用量对产品2-MNQ收率、转化率的影响，采用HPLC (外标法)测定产品2-MNQ的转化率和收率，得到最佳工艺条件为反应温度65℃、反应时间5 h、n(H2O2):n(2-MN)=26:1，此时，2-甲基萘的转化率为99%，产品收率为34%。本工作的创新点是使用原位红外技术验证反应机理和中间过程，即原料2-甲基萘经过氧乙酸氧化，发生环氧化反应生成中间体，之后重排生成2-甲基羟醌，继续氧化生成目标产物2-甲基-1,4-萘醌。该工艺具有简单环保、操作条件温和、原料易得等特点。

关键词: 2-甲基萘, 2-甲基-1,4-萘醌, 氧化反应, 绿色合成