Kinetics of Synthesizing Benzoic Acid 4-Nitrophenyl Ester by Solid-Liquid Phase-Transfer Catalysis

Abstract

The kinetics of synthesizing benzoic acid 4-nitrophenyl ester via solid-liquid phase-transfer catalysis was investigated. The operating conditions for investigation include agitation speeds, catalyst amounts, reaction temperatures, type of solvents, molar ratio of reactants, type of phase-transfer catalysts, volume ratio of aqueous to solvent, and so on. The reaction mechanism and apparent reaction rate constants were obtained from the experimental results. In the present study, the major investigation include quaternary ammonium salts and PEGs systems. In the quaternary ammonium salts system, the kinetics of sodium 4-nitrophenoxide with benzoyl chloride to produce benzoic acid 4-nitrophenyl ester via solid-liquid phase-transfer catalysis were investigated. The intrinsic reaction rate is very fast, so the reaction rate-determining step is ion exchange rate in the interface of solid-liquid phases. When the agitation speed exceeds 200 rpm, the mass transfer resistance at the solid-liquid interface can be neglected. Different phase-transfer catalysts were employed to compare their catalytic efficiency: TBAB>BTBAB>TBPB≒TBAI. The reaction rate increased with increasing amount of water. The experimential data were well described by the pseudo-first-order kinetics. The apparent activation energy in dichloromethane was obtained 11.5 kcal/mol. For the other PEG system, the kinetics of sodium 4-nitrophenoxide with benzoyl chloride to produce benzoic acid 4-nitrophenyl ester via solid-liquid phase-transfer catalysis were investigated. When the agitation speed exceeds 200 rpm, the mass transfer resistance at the solid-liquid interface can be neglected. Different molecular weights of PEG catalysts were employed to compare their catalytic efficiency: PEG1000>PEG600≒ PEG1500>PEG400>PEG2000. The experimential results were well described by the pseudo-first-order kinetic model. The apparent activation energy in dichloromethane was obtained 6.5 kcal/mol. Further, using methyl tert-butyl ether as the organic solvent, a kinetic model taking into account the deactivation behavior of the catalyst was proposed to describe the overall reaction successfully. The first-order kinetics with the deactivation function was employed to estimate the initial apparent rate constants and the deactivation constants. The kinetic model is described by t/-ln(1-Y)=(1/kapp,0)+(kd/kapp,0)*t Key words: Phase-transfer catalysis, Kinetic, Solid-liquid system, Deactivation, Benzoic Acid 4-Nitrophenyl Ester, Etherification本研究是在固-液相中合成苯甲酸4-硝基苯酯，在本反應系統中探討的變數有：觸媒添加量效應、攪拌效應、水量添加效應、有機溶劑的種類、不同觸媒種類、溫度效應等，並經由實驗結果推導出反應機構及求出反應動力學速率常數。 本研究主要內容分為兩部分，結果如下：在四級銨鹽系統中，探討對-硝基酚化鈉(Sodium 4-nitrophenoxide)與氯化苯甲醯(Benzoyl chloride)在固-液相系統中反應生成苯甲酸4-硝基苯酯的反應動力學。反應過程中本質反應速率很快，因此觸媒中間體的生成速率為速率決定步驟。實驗結果：當攪拌速率超過200 rpm時，固-液相界面之間的質傳阻力可以忽略不計。不同觸媒反應活性大小為TBAB>BTBAB>TBPB≒TBAI。添加水量愈多則反應速率愈快。實驗結果可用虛擬一階方程式完整描述此一系統。經Arrhenius’方程式可計算出以溴化四丁基銨為觸媒在二氯甲烷中得到的視反應活化能為11.5 kcal/mol。 另外一個系統是以聚乙二醇為觸媒合成苯甲酸4-硝基苯酯，實驗結果為：當攪拌速率超過200 rpm時，固-液相界面之間的質傳阻力可以忽略不計。不同觸媒反應活性大小為PEG1000>PEG600≒ PEG1500>PEG400>PEG2000。實驗結果可用虛擬ㄧ階方程式完整描述動力學模式。經Arrhenius’方程式可計算出以PEG1000為觸媒在二氯甲烷中得到的視反應活化能為6.5 kcal/mol。另外在使用第三丁基甲基醚為溶劑時會有衰退現象產生，可用下面示子描述，並可計算出其衰退常數及初始反應速率常數。 t/-ln(1-Y)=(1/kapp,0)+(kd/kapp,0)*t 關鍵詞： 相間轉移催化，動力學，固-液系統，衰退，苯甲酸4-硝基苯酯，酯化中文摘要 英文摘要 誌 謝 目 錄 圖 目 錄 表 目 錄 符號說明 第一章 緒論 1.1. 前言 1.2. 相間轉移催化反應簡介 1.3. 固-液相催化反應文獻回顧 1.4. 酯化反應 1.5. 研究目的與研究方法 第二章 實驗設備與步驟 2.1. 實驗藥品 2.2. 分析儀器 2.3. 實驗裝置 2.4. 產物之合成 2.5. 觸媒中間體之製備 2.6. 校正曲線 2.7. 反應動力實驗步驟 第三章 反應動力模式 3.1. 固-液相催化酯化反應機制 3.2. 四級鹽類觸媒系統之批式反應動力模式推導 3.3. PEG觸媒系統之批式反應動力模式推導 第四章 實驗結果與討論 4.1. 轉速效應 4.2. 四級鹽類相間轉移觸媒之催化酯化反應速率 4.3. 操作變數對四級鹽類催化酯化反應之效應 4.4. 操作變數對四級鹽類觸媒中間體變化之效應 4.5. PEG觸媒之催化酯化反應速率 4.6. 操作變數對PEG觸媒催化酯化反應之效應 第五章 結論 參考文獻 附 錄 A. 苯甲酸4-硝基苯酯1HNMR圖譜 B. 4-硝基苯基化四丁基銨1HNMR圖