2-甲基-6-乙酰基萘的合成及分子结构解析

Synthesis and molecular structure analysis of 2-methyl-6-acetylnaphthalene via the acylation of 2-methylnaphthalene

2-甲基-6-乙酰基萘(2,6-MAN)作为高性能聚酯材料(如聚萘二甲酸乙二醇酯PEN)的前驱体,其高选择性合成具有重要意义。以2-甲基萘(2-MN)为原料,乙酰氯(AC)为酰化剂,三氯化铝(AlCl_(3))为催化剂,采用正交试验法考察反应物配比、反应时间、反应温度、酰化液滴加温度对酰化过程的影响。采用重结晶法纯化产物,考察溶剂用量、降温速率对目标产物纯度的影响。质谱、红外、一维核磁及二维核磁结果显示,酰化主产物为含有C~6取代的乙酰基官能团的2,6-MAN。正交试验结果表明,反应物配比对酰化产物收率影响最大,酰化剂及催化剂量的不足会降低收率;反应温度对2,6-MAN纯度影响最大。当n(2-MN)/n(AC)/n(AlCl_(3))为1.00/1.20/1.45,反应温度为25℃、反应时间为4 h,酰化液滴加温度为-5~-2℃时,酰化产物收率达90.93%、2,6-MAN纯度为76.32%。以甲醇水溶液为溶剂提纯酰化产物时发现,溶剂用量较多和慢速程序降温可提高目标产物纯度。当溶剂与酰化产物质量比为5/1,慢速降温时可得到纯度大于98%的产品,满足工业氧化生产要求。

2-methyl-6-acylnaphthalene(2,6-MAN) is one of the most important precursors(such as polyethylene naphthalate PEN) for polyester materials with high performances,and its highly selective synthesis is of great significance.Using 2-methylnaphthalene(2-MN) as the raw material,acetyl chloride(AC) as acylating agent and aluminum trichloride(AlCl_3) as catalyst,the effect of the reactants ratio,reaction time,reaction temperature and addition temperature on the acylation process was studied by orthogonal experiments.The acylation products were further purified by recrystallization.The effect of solvent amount and cooling rate of solution on the product purity was investigated.The results from the analyses of GC-MS,FT-IR,1D-NMR and 2D-NMR show that the main component of acylation products is identified to be 2,6-MAN containing C~6-substituted acetyl.The results of orthogonal experiments show that the ratio of reactants has the most influence on the product yield.The insufficiency of acylating agent and catalyst causes the yield decrease.The reaction temperature shows the most significant effect on the 2,6-MAN purity.When the ratio of n(2-MN)/n(AC)/n(AlCl_3) is 1.00/1.20/1.45,the reaction temperature is 25 ℃,the reaction time is 4 h,and the addition temperature is-5 ℃ to-2 ℃,the resultant products yield can reach 90.93%,along with the purity of 2,6-MAN being 76.32%.When using methanol aqueous solution as solvent to purify the acylation product,the results show that high ratio of solvent/acylation product and slow cooling of the solution can improve the purity of the target product.When the mass ratio of methanol aqueous solution to acylation product is 5/1 and the slow cooling along with addition of crystal seeds is utilized,the resultant product with 2,6-MAN purity is above 98%,which can meet the oxidation need of 2,6-MAN in industry.