Catalytic esterolysis of p-nitrophenyl esters by optically active polymeric oximes

An optically active polymer containing oxime groups was prepared by partial quaternization of a copolymer of 4-vinyl pyridine and (+)(S)-4-methyl-1-hexen-3-one, with phenacyl bromide and subsequent reaction with hydroxylamine hydrochloride. This polymer was used as a catalyst for the esterolysis of esters of p-nitrophenol with aliphatic and aromatic carboxylic acids characterized by different steric and hydrophobic features. The detailed evaluation of kinetic parameters permitted identification of the main factors responsible for the catalytic behaviour.     

Catalysis at the toluene/water interface: shape-selective hydrolysis of esters having some rings and lactones promoted by octadecyl immobilized H-ZSM-5 catalyst

Shape-selective properties of octadecyltrichlorosilane-treated H-ZSM-5, abbreviated as H-ZSM-5-C₁₈, have been observed in the hydrolysis of esters having some rings and lactones in toluene-water solvent system. The shape-selectivity for the reaction has been evaluated by the ratio of the relative rate constants in comparison with the rate constant of methyl acetate. The selectivity became higher with increase in bulkiness of the substrate. Substrates having the minimum diameter larger than 6.5 Å, significantly larger in size than the pore openings of ZSM-5, could not react in this system.     

Liquid‐phase catalytic thermal cleavage of thiocarbonylthio end‐groups for polymers synthesized by RAFT polymerization: Influences of different solvents

Catalytic thermal cleavage of thiocarbonylthio end‐groups for RAFT synthesized polymers is usually accompanied by other side reactions such as chain‐scission and crosslinking. Occurrence of these side reactions depends on polymers, end‐groups, and oxidation–reduction property of reaction media in a liquid phase. Herein, well‐defined hydrophilic poly(4‐vinylpridine) (P4VP) and hydrophobic polystyrene (PS) are synthesized via a controlled RAFT polymerization in the presence of S‐1‐Dodecyl‐S′‐(R,R′‐dimethyl‐R″‐acetic acid) trithiocarbonates (DDMAT). Then their thiocarbonylthio end‐groups are cleaved through catalytic thermolysis in a liquid phase. Under the catalysis of Cu(0), all S‐containing groups can be removed at 165 °C in 3 h. To study the effect of solvent on thermolysis and microstructure of polymer, nitrobenzene of oxidation property and diethylene glycol of reduction property are chosen as solvents. Because of oxidizing property of nitrobenzene, Z groups of RAFT agent are eliminated at the same time that thiocarbonylthio end‐groups are removed. Therefore crosslinking among multipolymer chains occurs. While diethylene glycol is used as a solvent, no crosslinking occurs. Diethylene glycol is superior to nitrobenzene for synthesis of well‐defined polymer without S‐containing groups. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43992.