Study on the Synthesis of Diether Compounds via Phase Transfer Catalysis

• Main Authors: Yao-Hsuan Tseng, 曾堯宣
• Other Authors: Maw-Ling Wang
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/13157312010446831181

博士 === 國立中正大學 === 化學工程研究所 === 91 === In the present study, ether, di-ether, and dialkyl sulphide were synthesized by reacting bromoalkanes with 1-butanol, 4,4’-biphenol, and sodium sulfide (aqueous reactants) with bromoalkanes in an alkaline solution/organic solvent two-phase medium via phase transfer catalysis, respectively. The types of these reactions belong to series and parallel reactions. These products can be used as the additives of liquid crystal material and gasoline, liquid crystal material, perfume, and inverse phase transfer catalyst, respectively. The primary purposes of this thesis are to study the phase-transfer catalytic reactions of ether compounds, reaction mechanism, kinetics, distribution of active catalyst, mass transfer effect and other related theories. Several rigid conclusions were obtained from the experimental results: (a)All reactions in this work are di-substituted etherification reactions via extraction mechanism. In Section 1, the organic reactants have two substituted bromide groups. Oppositely, the aqueous reactants have the di-alkylatable oxygen and sulfur groups of in Section 2. (b)The biphasic etherification reaction was effectively enhanced in the mild condition via phase transfer catalysis. The most reactive catalysts were Aliquat 336 and TBAI in this work. (c)The products were purified by applying the methods of recrystallization and pressurized column chromatography to avoid the decomposition of products via distillation. (d)The pseudo steady-state hypothesis, pseudo first-order rate law, and two-film theory are successfully applied to built up the reaction mechanism. The rate constants were correctly calculated from the presented experimental data, initial rate approach, and computer program. (e)The two-phase mass transfer rate of the active catalyst is limited. The threshold values of the three reaction systems were 400, 250, and 350 rpm, respectively. The reaction was organic reaction controlled at the agitation speed over the threshold value. (f)The concentration of the active catalyst keeps at a constant value at an excess amount of the aqueous reactant. The organic reaction can be simplified as pseudo first-order rate. (g)As the results of kinetics, the rate was increased with the increase in temperature, amount of catalyst, organophilicity and symmetry of catalyst cation. Alkali salt is used to decrease solvation of active catalyst. It enhances the solubility and ionization of the aqueous reactants. However, the aqueous reactants were precipitated because of the same cation effect caused by using larger amount of alkali salt as described in Section 2. The recrystallization of sodium sulfide is induced at an excess amount of sodium sulfide. (h)The different reactivities of reactants and the active catalysts were due to the withdrawing ability of electron, electron density, and stereo hindrance. The reactions of a higher activated energy are more sensitive at a better reaction condition. (i)The phase transfer catalytic reactions were analyzed by fraction factorial analysis method (FFD). The five interaction factors: temperature-amount of alkali, temperature-volume of water, temperature-volume of solvent, temperature-agitation speed, and amount of catalyst-amount of alkali were screened out by fraction factorial analysis method.