Tetrabutylammonium benzoate, effect

Similarly to classical PTC reaction conditions, under solid-liquid PTC conditions with use of microwaves the role of catalyst is very important. On several occasions it has been found that in the absence of a catalyst the reaction proceeds very slowly or not at all. The need to use a phase-transfer catalyst implies also the application of at least one liquid component (i.e. the electrophilic reagent or solvent). It has been shown [9] that ion-pair exchange between the catalyst and nucleophilic anions proceeds efficiently only in the presence of a liquid phase. During investigation of the formation of tetrabutylammonium benzoate from potassium benzoate and tetrabu-tylammonium bromide, and the thermal effects related to it under the action of microwave irradiation, it was shown that potassium benzoate did not absorb micro-waves significantly (Fig. 5.1, curves a and b). Even in the presence of tetrabutylammonium bromide (TBAB) the temperature increase for solid potassium benzoate... 

During investigation of the formation of tetrabutylammonium benzoate from potassium benzoate and tetrabutylammonium bromide, and thermal effects related to this under the action of MW irradiation, it was shown that potassium benzoate did not absorb MW significantly (Fig. 6.1, curves a and b). Even in the pres-... 

The conversion of squaraine 19a to the rotaxane 18 D 19a causes a modest red-shift only in both absorption (10 nm) and emission (7 nm) but an approximately threefold decrease in quantum yield. The addition of two triazole rings (dye 19b) did not significantly alter the quantum yield of 17b (Table 4). A macrocycle-induced quenching effect was verified by fluorescence titration experiments adding aliquots of 18 to a solution of squaraine 17b in methylene chloride [58]. Treatment of the 18 d 17b psuedorotaxane system with the tetrabutylammonium salts of chloride, acetate, or benzoate leads to the displacement of squaraine 17b from the macrocyclic cavity and the nearly complete restoration of its fluorescence intensity. The 18-induced quenching of 17b does not support the utility of this system as a bioimaging probe however, the pseudorotaxane system 18 Z> 17b acts as an effective and selective anion sensor with NIR fluorescence. 

The effect of the anion on the copolymerization rate is controversial. Hilt et al.41 established for different sodium halides the following order of efficiency F < Cl < Br < J . This order was interpreted on the basis of the increase in nucleophilicity or polarizability of the anions. Sfluparek and Mleziva 43) observed that the reaction rate of the benzoate anion was about twice as high as that of the bromide anion in the copolymerization of epichlorohydrine with phthalic anhydride. On the other hand, Luston and Manasek56) did not detect any effect of the anion size on the copolymerization rate initiated by tetramethylammonium and tetrabutylammonium halides. 

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