2,6-萘二甲酸(2,6-NDA)是合成聚酯新材料聚萘二甲酸乙二醇酯(PEN)的重要单体，2,6-NDA结构的高度对称性使得PEN具有直链聚合物的特性，这种特性使得PEN在耐热性、阻气性能和化学稳定性等方面具备非常优越的性能。2,6-NDA的合成可通过氧化2-甲基-6-酰基萘得到，其制备过程中的关键步骤为β-甲基萘的酰基化反应。为了揭示β-甲基萘的酰基化反应过程和机理，以Lewis酸AlCl3为催化剂，采用丙酰氯和硝基苯分别作为酰化剂和溶剂对β-甲基萘的酰基化反应进行详细研究。β-甲基萘的酰基化反应结果表明，25 ℃下控制原料物质的量比n(β-甲基萘)∶n(丙酰氯)∶n(AlCl3)=1.0∶1.4∶1.7，在丙酰氯过量的前提下酰化反应5 h，β-甲基萘的转化率为92.53%，目标产物选择性达89.98%，反应得到的酰化粗品用15%的甲醇水溶液进行重结晶精制可得到纯度为99.99%的酰化纯品。采用气相色谱(GC)、质谱(MS)、红外(IR)、核磁(1H-NMR、13C-NMR)及二维核磁解析(gCOSY)对酰化纯品的分子结构进行了详细表征，分析了酰基化产物的官能团信息和分子结构骨架原子信息。结合Chemdraw软件的结构预测对比确认了酰化产物为2-甲基-6-丙酰基萘。β-甲基萘酰化机理分析表明，酰化剂与催化剂形成的活化络合物分子具有较大的尺寸，在进行Friedel-Crafts酰基化反应时，酰化剂与芳烃发生环上亲电取代反应所引起的空间位阻使得酰化剂只能进攻萘环的6号位，导致酰基化反应主要生成2-甲基-6-丙酰基萘。

The 2,6-Naphthalenedicarboxylic acid (2,6-NDA) is the precursor of polyester polyethylene naphthalate (PEN),and the highly symmetric structure of 2,6-NDA endows the straight-chain polymer with superior performance in heat resistance,gas blocking and chemical stability.The 2,6-NDA can be obtained by the oxidation of 2-methyl-6-acyl naphthalene which can be synthesized by 2-methylnaphthalene acylation.In order to understand the mechanism and the process of the acylation of 2-methylnaphthalene,the authors employed the 2-methyl naphthalene (2-MN) as reactant,the AlCl3 as catalyst and the propionyl chloride as acylating agent to implement the acylation reaction.Results showed that the 2-MN conversion rate could reach 92.53% and the product selectivity was 89.98% under the reaction conditions of acylation reaction at 25 ℃ for 5 h with the molar ration of n(2-MN):n(propionyl chloride):n(AlCl3)=1∶1.4∶1.7.15% methanol recrystallization processing could obtain 99.99% 2-methyl-6-propionyl naphthalene.The obtained pure product was systematically characterized to identify the molecular structure by using gas chromatography,mass spectrometry,infrared spectroscopy,1H spectrum,13C spectrum,two-dimensional nuclear magnetic resonance techniques and the ChemDraw software structure prediction.Based on the above structural characterization and combined with the structure prediction by using the ChemDraw software,the acylated product was identified to be the 2-methyl-6-propionyl naphthalene.The speculated mechanism of the 2-methylnaphthalene acylation indicated that the reason why the 2-methyl-6-propionyl naphthalene being the main acylated product is due to the steric-hindrance effect imposed by the large size complex molecule during the Friedel-Crafts acylated reaction.