盐酸催化合成α-萘乙酸甲酯汪朝阳;蒋姗姗;谢小莹【摘要】以α-萘乙酸、甲醇为原料,以浓盐酸为催化剂,通过酯化反应合成了植物生长调节剂萘乙酸甲酯.通过正交设计讨论了醇酸摩尔比、催化剂用量、反应时间等因素对酯化产率的影响.在α-萘乙酸50mmol,n(甲醇):n(α-萘乙酸)=25,催化剂用量为α-萘乙酸质量的17%,反应时间2.0h,酯化温度65℃～69℃的最佳反应工艺条件下,产率97.4%.%Using concentrated hydrochloric acid (HCl) as a cheap esterification catalyst, methylα-naphthylacetate, an important plant growth regulator, was synthesized from α-naphthylacetic acid and methanol. Through orthogonal test, the factors influencing reaction yield are discussed. Under the optimum reaction conditions (molar ratio of methanol to α-naphthylacetic acid 25, mass ratio of HCl to α-naphthylacetic acid 17%, reaction time 2h) the yield was 97.4%.【期刊名称】《合成化学》【年(卷),期】2004(012)006【总页数】4页(P603-605,610)【关键词】α-萘乙酸甲酯;浓盐酸;催化合成;α-萘乙酸;甲醇;酯化【作者】汪朝阳;蒋姗姗;谢小莹【作者单位】华南师范大学化学系,广东,广州,510631;华南师范大学化学系,广东,广州,510631;华南师范大学化学系,广东,广州,510631【正文语种】中文【中图分类】O626.32;O625.15As an important plant growth regulator, methyl α-naphthylacetate(MENA) is extensively used as a germination preventor for potato, and it is very important for the potato stockpile. At the same time, it is also an intermediate for other plant growth regulator[1].MENA is ordinarily synthesized through the esterification of α-naphthylacetic acid(NA) and methanol using different catalysts, such as solid super acid[2,3], and ion exchange resin[4]. Hoping for a cheaper and more effective catalyst, ferric chloride was successful used[5]. Concentrated hydrochloric acid(HCl) was an effective catalyst for esterificationa[6] and its application for the synthesis of MENA was investigated in this paper.1 Experimental Section1.1 Instruments and reagentsThe purity of MENA was determined with a Japan Shimadzu GC-9A gas chromatograph. The structure of MENA was characterized with a USA PE company SP3-200 infrared spectrometer(liquid film), and a Japan R-24B HITACHI NMR spectrometer(60MHz, solvent CDCl3, internal standard TMS). The refraction index(n) was tested with a Shanghai optical instrument factory 2W Abbe refractor.NA, chemical purity, was purchased from China pharmic group Shanghaireagent company. Methanol, analytic reagent, was purchased from Tianjin Damao chemical instrument providing-station. Concentrated hydrochloric acid(HCl,C．P．), was purchased from Guangzhou chemical reagent factory. Other reagents, C．P． or A，R． were all commercially obtained.1.2 Synthetic methodAccording to literatures[3，5], NA 9.3g(50mmol), and a certain metric methanol and catalyst HCl were added together into a 100mL flask. After refluxing a certain time, the esterification was terminated, and the excessive methanol was distilled out. Pouring the residue into water, the organic component was extracted out by ethyl ether.The organic phase was first washed with 5%(weight percent) NaHCO3 solution to pH=7, then the saturated NaCl solution. Drying the organic phase with anhydrous Na2SO4, the ether was removed by an exhaustive distillation to gave yellowish transparent viscous liquid product MENA. 1.3 Product analysisThe purity of MENA was over 98.5% by GC. Its was 1.5945, and the datum is consistent with that of literature[2]. The structure of product was also identical with that of literature[5], and the determined data were shown as followed: IR:υ=3051(ArH), 2948(saturate C-H),1735(C=O)cm-1． 1H NMR:δ=3.53 (s,3H,OCH3), 3.95 (s，2H,CH2),7.23～8.00(m，7H,ArH).2 Results and DiscussionDuring the esterification, the excessive methanol could effectively control the reaction temperature[5]. When the temperature reached the boiling point of methanol(65℃), reflux began, and then the temperature waslightly fluctuating between 68℃ and 69℃ till termination. So, the main factors influencing on the yield of esterification were catalyst quality, mole ratio of methanol to NA, and reaction time. According to literatures[4,5], an orthogonal test result and analysis was shown as Table 1.Table 1 The Result and Analysis of the Orthogonal Test Result* NumberA/mol ∶molB/%C/hYield/%122.5(1)15(1)1.5(1)94.82117(2)2.0(2)94. 13119(3)2.5(3)93.0425.0(2)1294.9522395.1623194.0727.5(3)1393.6832194.2 933294.7K1jK2jK3j281.9284.0282.5283.3283.4281.7283.0283.7281.7Influenc es:A>C>BK1j/3K2j/3K3j/393.9794.6794.1794.4394.4793.9094.3394.5793.90 Conclusion:A2B2C2Rj0.700.570.67*A. mole ratio of methanol to NA， B. weight percent of HCl to NA，C. reaction timeIt is obvious that, the biggest influencing factor is mole ratio of methanol to NA, then reaction time. Maybe the catalyst has good catalytic efficiency, so the quality of HCl is the smallest factor.At the same time, the optimal condition is given as followed: mole ratio of alcohol to acid 25, weight percent of HCl to NA 17%, and reflux time 2.0h. Though the combination is not included in the above orthogonal test design, the conclusion is verified by the following 3 group tests.2.1 Influence of catalyst quality on yieldMaking NA 50mmol, mole ratio of alcohol to acid 25, and reaction time 2.0h changeless, changing the weight percent of HCl to NA, the influences of catalyst quality on yield is shown as Table 2.Table 2 Influence of HCl Quality on EsterificationYieldW/%*1315171921Yield/%94.095.097.494.994.7*weight percent of HCl to NAIt is obvious that, with the increase of catalyst quality, the yield first increases. When the weight percent of HCl to NA is more than 17%, the yield decreases. Therefore, the suitable quality is 17%.2.2 Influences of mole ratio of alcohol to acid on yieldChanging the mole ratio of methanol to NA, but making NA 50mmol, weight percent of HCl to NA 17%, and reaction time 2.0h changeless, the influences of mole ratio of alcohol to acid on yield is shown as Table 3. Table 3 Influence of Mole Ratio of Methanol to NA on Esterification YieldM*20.022.525.027.530.0Yield/%88.394.197.495.795.6*Mole ratio of methanol to NAIt is obvious that, with the increase of mole ratio of methanol to NA, the yield increases. But when the mole ratio of methanol to NA is more than 25, the yield decreases. Therefore, the suitable ratio is 25.The esterification is a reversible reaction, so the bigger mole ratio of alcohol to acid is beneficial, especially for the existence of the huge steric hindrance in NA. At the same time, in this esterification, methanol is not only a reactant, but also used as the recyclable solvent[5]. In a word, the result of mole ratio of alcohol to acid 25 is reasonable.2.3 Influence of reaction time on yieldChanging reflux time, but making NA 50mmol, weight percent of HCl to NA 17%, and mole ratio of methanol to NA 25 changeless, the influences of reaction time on yield is shown as Table 4.Table 4 Influence of Reaction Time on Esterification YieldReactiontime/h0.51.01.52.02.5Yield/%76.092.194.197.495.1The velocity of esterification is slow, and the longer time is advantageous to the higher yield, but also means more heating energy exhaust. It is obvious in Table 4, with the increase of reaction time, the yield increases. But when the time passes 2h, the yield decreases. Therefore, the suitable time is 2h.3 ConclusionsStarting from α-naphthylacetic acid and methanol, and using concentrated hydrochloric acid(HCl) as a catalyst, methyl α-naphthylacetate could be synthesized. Under the optimum reaction conditions(molar ratio of methanol to α-naphthylacetic acid 25, mass ratio of HCl to α-naphthylacetic acid 17%, and reaction time 2h) the yield is 97.4%. 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