Abstract
In the present study, polytrifluoroethoxycyclotri-phosphazene wassynthesized by reacting 2,2,2-trifluoroethanol withhexachlorocyclotriphosphazene by phase transfer catalysis in an organicsolvent and alkaline solution. The synthesized products can be used aspressurized hydrulic fluids, flame retartants and lubricants.The purpose of the present study is to understand the substitutionreaction of chloride from hexachlorocyclotriphosphazene bytrifluoroethanol by phase transfer catalysis. The kinetics, mass transfereffect and effect of concentration in each p hase are discussed. Severalrigid conclusions were obtained:(i) The substitution reaction was enhanced and the hydrolysis ofhexachlorocyclotriphosphazene decreased by adding a small quantity ofphase transfer catalyst. An effective method of pressurized columnchromatography was provided to separate the six distributed products. Thereaction followed a trans-nongeminal replacement pattern with no otherisomers. Furthermore, the electronic density effect and the steric effectwere employed to explain the relative reaction reactivity of the sixdistributed products.(ii) Changing the initial concentration of hexachlorocyclotriphosphazeneaffected the value of pseudo first order reaction rate constant. Hence,the reaction rate was limited by the mass transport of phase transfercatalyst in the two-phase reaction. Pseudo first order reaction model wassuccessfully used to explain the relation between reaction parameters andpseudo first ordeer reaction rate constant.(iii) Based on the experimental data, the reactivities of all kinds ofcatalysts in the organic phase were the same for the reaction mechanism.The effectiveness of a phase transfer catalyst depends highly on theorganophilicity. The retarding effect of free acids on the substitutionprocess can be attributed to the masking of the anion and the deactivationof the anion via hydrogen bonding.(iv) In order to overcome the difficulty of separating of the catalystfrom the final product, the catalyst was immobilized on a polymer support,i.e., triphase catalyst. The polymer support is the copolymer of styreneand chloromethylstyrene, using divinylbenzene as a curing agent. The masstransfer limitation influences the triphase reaction rate. The particlediffusion and intrinsic reactivity limit the displacement reaction in theorganic phase. The film diffusion of the aqueous phase limits in theion-exchange step. The organophilic structure of polymer support increasedthe displacement reaction in the organic phase, but the rate determiningstep is the noncontineous phase between aqueous phase and organic phase.(v) In addition, the reaction rate increased by increasing theconcertration sodium trifluoroethoxy which is water-reactant. Increasingthe concentraction of salts, sodium chloride and sodium hydroxide,decreased the reaction rate.本論文所研究之反應系統為六氯環三偶磷氮(hexachloro-cyclotriphosphazene;(NPC12)3) 和三氟乙醇(2,2,2-trifluoroethanol; HOCH2CF3)在油相溶劑╱水相鹼性溶液，藉著相間轉移觸媒進行置換反應。因反應為系列反應(series reaction) ，產物為多三氟乙醇基環三偶磷氮(poly(2,2,2-trifluoro-ethanoxy)cyclotriphosphazene)，其主要用途為液壓流體，阻燃劑和潤滑劑等。在本論文裡，主要探討利用相間轉移觸媒技術進行六氯環三偶磷氮和三氟乙醇之合成置換反應，動力學行，質傳效應，水油兩相濃度現象及理論之相關問題。由研究中獲得下列肯定之結論如下：(i) 本論文以相間轉移觸媒技術進行六氯環三偶磷氮和三氟乙醇之置換反應，有效的增進反應速率且消除了六氯環三偶磷氮水解現象。由加壓管層析法得產物之反應途徑為反式－非孿式(trans-nongeminal)途徑，藉著動力學參數（反應速率常數，活化能和熵）和電子效應(electronic effect) 及立體障礙效應(steric effect) 合理解釋此系列反應置換型態。(ii)在兩相反應，因虛擬一次反應速率常數(pseudo first order reaction rateconstant) 會隨著最初加入之油相反應物六氯環三偶氮濃度不同而改變，因而得知在兩相反應中相間轉移觸媒在兩相界面質量傳送受阻。推導出虛擬一次反應模式，成功地解釋兩相反應參數和虛擬一次反應速率常數之關係。而且得知兩相質量傳送主要阻力，乃來自於氯化四丁基銨由油相傳至水相之質量傳送。(iii) 由實驗知，相間轉移觸媒（四級銨鹽）其反應能力相差不多，最大不同在其親油性性質。在反應條件下加入過量的酸（三氟乙醇），則因其和三氟乙醇基四丁基銨複合，會使得反應能加降低。(iv)由於兩相相間轉移觸媒不易回收，故把相間轉移觸媒固定於由苯乙烯(styrene )，氯甲基苯乙烯(chloromethy1-styrene)和二乙烯基苯(diviny1benzene)所合成的高分子擔體上，以利於回收，而成為三相觸媒。在本論文利用三相觸媒合成偶磷氮化合物，發現油相置換反應受到擔體顆粒擴散和本質化學反應控制，水相離子交換反應受到薄膜擴散控制。在所研究的三相觸媒擔體結構，親油性結構有利油相置換反應，但擔體內的水油兩相分配卻為決定反應速率之主要因素。(v) 在反應中水相具有三氟乙醇鈉，氫氧化鈉和氯化鈉三種鹽類，除三氟乙醇鈉為反應物，增加其量會增加反應速率外，不論在兩相或三相反應，過量的鹽類濃度將會改變有效烷氧基相間轉移觸媒濃度都不利於反應速率。