Synthesis Of Distyryl Fluorescent Brightener By Hornerwadsworth-emmons Reaction In Phase Transfer Catalysis System And Reaction Mechanism

Distyryl fluorescent whitening agent(FWA) which had the advantage of quantum efficiency, good anti-fatigue performance and fluorescent adjustable had been one of the common functional additives and an indispensable part for many high-grade products. As demand increased, distyryl FWAs had accounted for 10% of the FWA annual output. Horner-Wadsworth-Emmons(HWE) reaction was the most popular and powerful method for producing distyryl FWA in industry. In HWE reaction, phosphonate was deprotonated by the alkaline agent and then the condensation reaction of the generated carbanion and carbonyl group proceeded. Because considerably different polarity between the reactants in the deprotonation reaction and the bond-forming reaction, the dipole aprotic solvent was the most common solvent for HWE reaction. However, not only following problems was caused by dipole aprotic solvent, such as the high cost, high dissolubility of the product and difficult recycle and dehydration, but also the price of distyryl FWA was 10-20 higher than that of other FWAs. With the increased emphasis on energy conservation and emission reduction for the production process of Distyryl FWA,it was important to develop a new procedure for HWE reaction. Condensation of the carbanion in HI-PTC system proceeded with the non-polar solvent and inorganic alkaline agent and had the advantage of high reaction rate, yield and selectivity. In this study, HI-PTC system was chosen to synthesize stilbene and distyryl compounds with weakly acidic phosphonate and disphosphonare, the mechanism of HWE reaction in PTC system was investigated and the structure-function relationship for distyryl compounds was established, These result can provide an high-efficiency and energy saving way for HWE reaction in industry. The main contents and conclusions are summarized as follows:(1) HWE reaction in Liquid-liquid and solid-liquid PTC systemA series of stilbene and distyryl compounds were synthesized in liquid-liquid(LL) and solidliquid(SL) PTC system with benzaldehyde derivates and weakly acidic phosphonate as reactants. Effects of the structure of the reactants and the catalyst on the yield and geometric selectivity of HWE reaction were investigated. The results showed that electronic effect of the substitute group in benzaldehyde derivate was the dominate factor affecting the yield of HWE reaction. The yield for HWE reaction of benzaldehyde with electron-donating group was higher than 90%, whereas for HWE reaction of benzaldehyde with electron-withdrawing group was 20%-80%, because of the cannizzaro reaction of benzaldehyde. The kinds of the substitute group had little influence on the geometric selectivity of HWE reaction. Only was Z-stilbene founded in the reaction of diethylbenzylphosphonate with benzaldehyde containing ortho-chlorine group, and the structure of the catalyst could also influence the geometric selectivity in these reactions. There was a little third phase in LLPTC system when the usage of the catalyst was only 6% of phosphonate, thus LLPTC system was converted into third-liquid PTC(TLPTC) system. Similarly, SLPTC system could be transformed into solid-liquid-liquid(SLL) PTC system and SLLPTC system showed a higher reaction rate than SLPTCsystem.(2) HWE reaction mechanism in third-liquid PTC systemIn TLPTC system, experiments on the interfacial tension between the organic phase and 50%(weight/weight) NaOH aqueous phase and H-D exchange reaction for the weakly acidic phosphonate were carried out for studying the deprotonation reaction of the phosphonate. The nature and the generation procedure of the third phase were explored by investigating the composition of the third phase and effect of the reaction parameter on the formation of the third phase. Based on the distribution of the reactant and the ion-pair, the role of the third phase, the catalytic cycle in TLPTC system was analyzed. It was found that the phase transfer catalyst did not involve the deprotonation process and phosphonate molecules were adsorbed on the surface of the aqueous phase and reacted with the OH- in the aqueous phase. The deprotonation reaction was in equilibrium. In this TLPTC system, the reaction mechanism involved in the deprotonation of phosphonate, the generation and transfer of the carbanion ion-pair, the organic phase bond-forming reaction and the third phase bond-forming reaction. The actual catalyst was PTC+PO- and PTCX, which concentration was 10-times higher than that in the organic phase. Although the reaction rate was 1.7-time of that without third phase, the ion-pair still distributed into both the organic phase and the third phase.Kinetic model which consisted of parallel reactions(the organic phase reaction and the third phase reaction) and tandem reaction(generation of ion-pair and bond-forming reaction in the organic phase reaction cycle) was presented. Effect of the reaction parameter on the each catalytic cycle reaction rate constant and the contribution ratio of the organic reaction cycle to the third phase reaction cycle were investigated by the kinetics experiment. It was found that there was a competitive relationship between these two cycles and the contribution ratio was determined by the distribution of the carbanion ion-pair from the third phase into the organic phase. The contribution of the third phase reaction was 3-9 higher than that of the organic phase, and the organic reaction can be neglected when the usage of phosphonate was excess to that of the benzaldehyde. Meanwhile, the induction period existed in the whole process of the HWE reaction. In TLPTC system, the size of the catalyst cation, accessory parameter and lipophilicity showed a linear relationship with stoichiometric reactivity of the carbanion-ion pair, ion-exchange reactivity of the catalyst in the third phase and the contribution ratio between both cycles, respectively.For the induction period existed in HWE reaction, effect of reaction parameter on the induction time and the initial reaction rate were investigated for exploring the generation reason of the induction period; the difference between catalytic activity between TBA+PO- and TBAB through the model ion-exchange reaction of TBAB and NaPO was calculated. It was showed that the generation of new catalyst with high catalytic activity(TBA+PO-) was the reason of the induction period and the ion exchange selective extraction coefficient for the carbanion to PO- was 2.6 time of that for carbanion to Br-. The anion cycle for HWE reaction in PTC system was consisted of POcycle and the Br- cycle, which corresponded to the autocatalytic reaction induced by TBA+PO- and instinct reaction catalyzed by TBAB. Kinetic model of the anion cycle in HWE reaction was deduced and the nature of each cycle was investigated utilizing the kinetics experiment of different parameters. The results showed that rate-determining step in autocatalytic cycle was the ion-exchange reaction between the catalyst and the carbanion, whereas in instinct cycle was the transfer of the ion-pair. Catalytic activity was related to lipophilicity of the catalyst for the autocatalytic cycle, whereas was lipophilicity and accessory parameter for the instinct cycle. The ion-exchange reaction of TBA+PO- and NaX in the anion cycle was also dependent on the kind of NaX, especially the composition of both instinct catalyst and autocatalytic catalyst was changed.(3) HWE reaction mechanism in solid-liquid PTC systemFor exploring the mechanism of HWE reaction in SLPTC system, the absorption behavior of the reactant and the catalyst on the interfacial region, effect of the reaction parameter on the apparent reaction rate constant were investigated. Accordingly, the kinetic model was deduced, the ratedetermining step for HWE reaction was confirmed and effect of reaction condition parameters on the reaction rate constant was analyzed. It was found that the reaction mechanism involving in deprotonation of phosphonate, generation and transfer of the carbanion ion-pair, the bond-forming reaction, which was similar to that in the organic phase cycle in TLPTC system. The deprotonation reaction was induced by solid NaOH and the rate-determining step in SLPTC system was the bondforming reaction, but the apparent reaction rate constant was determined by the stoichiometric reactivity of the carbanion ion-pair and the equilibrium concentration of the ion-pair in the organic phase. The reaction rate was more dependent on the stoichiometric reactivity of the carbanion ionpair when the temperature and the lipophilicity of the catalyst cation were changed, whereas the equilibrium concentration of the ion-pair in the organic phase when other reaction parameters changed. The apparent reaction rate constant in SLLPTC system was 0.5 time higher than that in SLPTC system because of the increasing equilibrium concentration of the ion-pair in the organic phase(4) Relationship between the structure and application performance for distyryl fluorescent whitening agentsFifteen 1,4-distyrylbenzene(DSB) and 4,4’-distyrylbiphenyl(DSBP) derivates were used as FWA to whiten the polyester fabric and cotton fabric. The whiteness, Tw value and the critical concentration were used to explore their application performance. Effect of molecule optical property in the fiber on the application performance was investigated by emission spectra, excitation spectra and reflectance spectra. It was found that electronic effect of the substitute group and the aggregation morphology played the key roles on the application performance of DSB and DSBP derivates. Distyryl derivates with electron-donating substitute which had poor polarity were difficult to dye the fiber and were prone to adhere to the surface of the fiber, whereas distyryl derivates with electron-withdrawing substitute could diffuse into the fiber. Bathochromic shift in the emission spectra with various usage of FWA revealed that the arrangement of FWA molecule existed in the fiber. Bathochromic shift was 1-5nm for the amorphous arrangement, whereas was 10-25 nm for Htype arrangement. For DSB molecule, H-type arrangement still had a high quantum yield due to the relatively small size and the emission light could be observed in the wave band between 450nm-475 nm resulting in the yellow-green hue and poor whitening performance. Fluorescent quenching for DSB and DSBP FWAs in polyester was caused by the H-type arrangement because of their poor molecular diffusivity Fluorescent quenching for DSBP FWA in cotton was caused by the inner filter effect of the adjacent molecules, whereas by both the inner filter effect and H-type aggregate for DSB FWAs...