Witold Kuran

Synthesis of functional polycarbonates by copolymerization of carbon dioxide with allyl glycidyl ether

Functional aliphatic polycarbonate was synthesized by copolymerization of carbon dioxide and allyl glycidyl ether in the presence of a catalyst system based on ZnEt 2 and pyrogallol at a molar ratio of 2:1. The polycarbonate obtained was oxidized with m-chloroperbenzoic acid to give poly(epoxycarbonate). These polymers were degraded in an aqueous buffer of pH 7.4 at 37°C. Hydrolytic degradation was monitored by determination of the weight loss.

Synthesis and Modification of Functional Polycarbonates with Pendant Allyl Groups

Functional aliphatic polycarbonates with pendant allyl groups were synthesised by copolymerization of carbon dioxide and allyl glycidyl ether (AGE) in the presence of a catalyst system based on ZnEt2 and pyrogallol at a molar ratio 2 : 1. The functionality of some polycarbonates was reduced by replacing a part of allyl ether with saturated glycidyl ether, i.e., butyl glycidyl ether (BGE) or isopropyl glycidyl ether (IGE). Polycarbonates obtained by the copolymerization of AGE and CO2 or by the terpolymerization of AGE, IGE and CO2 were oxidized with m-chloroperbenzoic acid to their respective poly(epoxycarbonate)s. The influence of the AGE/ΣGE ratio in the polycarbonates, the polymer concentration in the reaction solution and the duration of the reaction on the conversion of allyl groups into glycidyl ones was examined. A tendency to gelation of the initial and oxidized polycarbonates during storage was observed. The initial polycarbonates and their oxidized forms were degraded in aqueous buffer of pH = 7.4 at 37°C. The course of hydrolytic degradation was monitored by the determination of mass loss.

Ethylzinc hydroxide as an intermediate in the reaction of diethylzinc with water

Abstract The diethylzinc/water ( 1 1 mol) reaction in 1,4-dioxane as solvent has been studied by applying the cryoscopic method for molecular weight determinations to the products formed in the reaction solution. An ethylzinc hydroxide dimer was found to be formed as an intermediate in the reaction system during fast ethane elimination. Monomeric ethylzinc[tri(oxyzinc)] hydroxide was found to be the main product of the subsequent reaction of this intermediate, with further ethane elimination. A mechanism for the latter reaction, involving the formation of a transient ethylzinc hydroxide tetrameric species, is proposed. The reaction pathway in the diethylzinc/water ( 2 1 mol) system is also discussed. The formation of ethylzinc[tri(oxyzinc)] hydroxide, as in the 1 1 system, followed by the subsequent reaction of this compound with diethylzinc gave further ethane elimination and lead to ethylzinc[tri(oxyzinc)] ethylzinc oxide as the main product, is the proposed route in this case. In contrast to diethylzinc, which is too weak a Lewis acid to react with the ethylzinc hydroxide dimer, trimethylaluminium was found to undergo reaction with it in 1,4-dioxane solution, with fast methane and ethane elimination.

Reactions of organoaluminium compounds with π-benzoquinone

Abstract The reactions of π-benzoquinone (BQ) with alkylaluminium compounds of the R 3 Al (R = Et, i-Bu) and RAlCl 2 (R = Me, Et, i-Bu) type have been investigated. It was found that hydroquinone and a respective alkylhydroquinone are formed after hydrolysis, from the reaction of BQ with R 3 Al; hydroquinone and a respective p -alkoxyphenol are formed from reaction of BQ with RAlCl 2 (R = Et, i-Bu). In addition to the products mentioned in the reactions above, oligomerization compounds and products resulting from the reaction of BQ with toluene (when used as a solvent) were obtained. With the aid of ESR studies it was shown from the reaction of BQ with RAlCl 2 that aluminium derivatives of semibenzoquinone are formed On the basis of the results obtained, a carbanionic mechanism for the reaction of BQ with R 3 Al (1,4-addition) and a radical mechanism for the reaction of BQ with RAlCl 2 (1,6-addition) are proposed and discussed.

Investigations on the Monomer Distribution in Maleic Anhydride-Propylene Oxide Copolymers Obtained by Ethylzinc Catalysts

Abstract The copolymerizations of maleic anhydride (MA) and propylene oxide (PO) were carried out in toluene, dioxane, diethoxyethane, or dimethyldigol solution in the presence of ethylzinc compounds EtZnX (X = Et- or substituted phenoxy group). On the basis of the 1H-NMR data of copolymers and VPC of the products of their hydrolysis, it was found that donor solvents and X substituents involving CH3O-, Cl-, or CH3CO- donor groups in the ortho position of the aromatic ring (e.g., X = 2-CH3OC6H4O-, 2,6-(CH3O)2C6H3O-, 2-CH3COC6H4O-, etc.) caused an increase in the number of alternating sequences in copolymers chains. In the reaction of MA and PO in tetrahydrofuran (THF) solution, the above-mentioned zinc compounds gave highly alternating MA-PO-THF terpolymers.

Reactions of ethylaluminium compounds with p-chloranil

Abstract Reactions of ethylaluminium dichloride, diethylaluminium chloride and triethylaluminium with p-chloranil have been investigated. Tetrachlorohydroquinone and p-ethoxytetrachlorophenol are the main reaction products after hydrolysis. Ethane, ethylene, butane, hexane, octane, higher aliphatic hydrocarbons, products of the chlorine substitution by an ethyl group in a molecule of p-chloranil or tetrachlorohydroquinone, and ethyltoluene or benzyltoluene isomers (when toluene was used as a solvent) may also be formed depending on the type of reactants and reaction conditions. The reactions with p-chloranil of the ethylaluminium compounds studied were found to proceed involving in the first step the formation of donor—acceptor complexes via the carbonyl group. These complexes were found to undergo reactions of two basic types. The first one is a homolytic dissociation of the AlC bond with the formation of an aluminium derivative of semiquinone and an ethyl radical. The second type of reaction is the hydrogen transfer from the ethyl group bonded with the aluminium atom to the carbonyl group of quinone with the elimination of ethylene. The reaction course leading to the formation of tetrachlorohydroquinone and p-ethoxytetrachlorophenol is proposed and discussed.

Reactions of methylaluminium compounds with alkyl chlorides

Abstract The reactions of methylaluminium dichloride, dimethylaluminium chloride, and trimethylaluminium with vinyl chloride have been investigated. Of themethylaluminium compounds investigated, the dichloride reacted most readily. This reaction, carried out in n-heptane as solvent or without a solvent, produces chiefly cuprene and isobutane and a number of hydrocarbon and chlorohydrocarbon by-products. Dimethylaluminium chloride and trimethylaluminium react with vinyl chloride much less readily than methylaluminium dichloride; propylene and its oligomers are the major products. The mechanisms of the reactions of the individual methylaluminium compounds with vinyl chloride have been discussed on the basis of the experimental reaction data and NMR spectra. The decomposition of vinyl chloride by the Ziegler-Natta original and modified systems has been considered.

Kinetics and mechanism of the reactions of diethylzinc with phenols in cyclic ethers

Abstract Reactions of diethylzinc and phenols (phenol, 2-ethylphenol, 2-chlorophenol, 3-ethylphenol, 3-chlorophenol, 4-ethylphenol and 4-chlorophenol) have been carried out in tetrahydrofuran and 1,4-dioxane as solvents. Monomeric ethylzinc phenoxide has been found to be a product of the diethylzinc and phenol (1:1) reaction in 1,4-dioxane solution. Kinetic studies on the ethylzinc phenoxides and phenols reaction in tetrahydrofuran solution established the rate constants and the S E i mechanism of the reaction.

Synthesis of novel monomeric zinc—oxygen compounds containing diethylzinc and pyrocatechol or saligenin moieties

Abstract Reactions of diethylzinc with dihydric phenols such as pyrocatechol and saligenin in a molar ratio of 1 1 yield zinc pyrocatecholate and ethylzinc 2-hydroxymethylphenoxide, whereas a molar ratio of 3 2 gives zinc bis(2-ethylzincoxyphenoxide) and zinc bis(2-ethylzincoxyphenylmethoxide), respectively. The latter ethylzinc-oxygen compounds, containing zinc diphenoxide — or zinc dimethoxide — units complexed internally by ethylzinc groups, form monomeric species in 1,4-dioxane.

Structures of the products of the reactions of diethylzinc with trihydric phenols

Abstract Reactions of diethylzinc with 1,2,3-trihydroxybenzenes containing substituent X (X = H, C 2 H 5 , C 6 H 11 , C(CH 3 ) 3 , Cl, Br, COCH 3 ) in the aromatic ring at a 2/1 molar ratio have been carried out in tetrahydrofuran and 1,4-dioxane solutions. The kinetics of the reactions have been studied and the products have been characterized by means of 1 H NMR spectroscopy and cryoscopy. The structures of the intermediates and the final products of the reactions were determined.