Dramatic Enhancement of Superacid-Catalyzed Polyhydroxyalkylation Reactions

Abstract

Complementary theoretical and experimental studies of the consecutive steps of superacid catalyzed polyhydroxyalkylation reactions have been carried out. Calculations for the superacid catalyzed polyhydroxyalkylation of trifluoroacetone and trifluoroacetophenone with aromatic hydrocarbons explained a number of experimental facts within a single theoretical framework of monoprotonation. The principal factors affecting kinetics of superacid mediated hydroxyalkylation were shown to be as follows: (i) the acidity of the superacid affecting protonation energy of carbonyl components; (ii) the electrophilicity of carbonyl components; and (iii) the nucleophilicity of aromatic components. The modification of those factors allows for tuning of the reactivity of carbonyl and aromatic components; thereby, reaction kinetics are controlled. The conclusions were confirmed by the experiments. Theoretically predicted stoichiometrically imbalanced polymerizations of trifluoroacetone, trifluoroacetophenone, octafluoroacetophenone, and isatin with nonactivated, aromatic hydrocarbons gave high-molecular-weight polymers with a very small excess of the carbonyl compound. The main reasons contributing to the polymerization accelerations were found to be an increase of the first, rate-determining step reaction, and a high efficiency of the superacid catalyzed polyhydroxyalkylations. The present work has thus opened a new route to preparations of polymers of linear, hyperbranched, or hybrid (e.g., linear−hyperbranched) architecture by operating on structural parameters and reaction conditions.

Poly(arylene alkylene)s with pendant N-spirocyclic quaternary ammonium cations for anion exchange membranes

“…37 Because the rst step is rate-determining, the presence of a small excess of the ketone monomers dramatically enhances the polymerisation rate and the molecular weight of the resulting polymers. 36,38 However, using too large excess of ketones may instead lead to crosslinking and gelation. 38 Consequently, we used an excess of the ketones corresponding to 10-15 mol% of the biphenyl in the present copolycondensation.…”

“…36,38 However, using too large excess of ketones may instead lead to crosslinking and gelation. 38 Consequently, we used an excess of the ketones corresponding to 10-15 mol% of the biphenyl in the present copolycondensation. The resulting precursor copolymers containing TFAp and TFAc residues are denoted as PBPmPh and PBPmMe, respectively, where m indicates the mol% of biphenyl piperidine units, as calculated from 1 H NMR spectra ( Fig.…”

Synthesis and Characterization of Sulfonated Poly(Phenylene) Containing a Non-Planar Structure and Dibenzoyl Groups

“…Superacid polymerization products have high molecular weight without moisture but are easily crosslinked due to the high reactivity [25]. The nickel-catalyzed coupling reaction is more sensitive to moisture than the acid reaction but it is possible to have stable reaction products with high molecular weight.…”

Synthesis of hyperbranched polymers with controlled degree of branching

“…Such an interaction of these cations can only exist in a superacid medium, resulting in extremely reactive dication species in the condensed state. Olah et al 98 and Shudo and colleagues 99 suggested that a similar dication intermediate was predominant in the Friedel-Crafts reaction of the carbonyl compound with benzene in a superacid, although Fomine and colleagues 109 and Zolotukhin and colleagues 110 proposed a different mechanism by calculation, resulting in only the monocation intermediate without the formation of a dication. On the basis of Olah's proposal, in addition to the results of the model reaction between 2,2,2-trifluoroacetophenone and anisole in TFSA, the mechanism is postulated as shown in Scheme 22(a), in which the diprotonated carbonyl compound in a superacid condenses with anisole to yield an intermediate monocation compound, the reactivity of which is lower than that of the dication.…”