J. Málek

Bio: J. Málek is an academic researcher. The author has contributed to research in topics: Nucleophilic substitution & Catalysis. The author has an hindex of 1, co-authored 1 publications receiving 8 citations.

Kinetics and mechanism of the reaction of aromatic carboxylic acids with ethylene oxide in protic and aprotic dipolar solvents in the presence of tertiary amines

Abstract: Aromatic carboxylic acids react with ethylene oxide in the presence of tertiary amines as catalysts both in protic and in aprotic solvents to give the corresponding 2-hydroxyethyl esters by the amine- and acid-catalysed parallel reactions. In protic solvents, the acid-catalysed reaction is first-order in both the acid and ethylene oxide and its rate correlates with the acid strength by Br0nsted equation with the constant corresponding to a value of 0-62. The parallel aminecatalysed reaction of the acids with x>K^ ^ 3-99 is in these solvents first-order in both ethylene oxide and the amine, and the Br0nsted ci.2 constant has a value of 0-34. In the amine-catalysed reaction of the acids with pAT^ 318 there is a change in the nature of the rate-deter­ mining step; the reaction of the acids with pisTg ^318 proceeds solely with the acid participating in the rate-determining step of the amine-catalysed reaction which is first-order in the acid, ethylene oxide, and tertiary amine. Of the two parallel reactions occuring in protic solvents, the amine-catalysed one has the higher activation energy and by about 6 to 7 orders of magnitude higher values of the preexponential factor. In aprotic dipolar solvents the acid-catalysed reaction is first-order in both the acid and ethylene oxide, and the Bronsted constant a'^ has a value of 096. The amine-catalysed reaction is in this case first-order in the acid, ethylene oxide, and tertiary amine, and its kinetics does not change with the acid strength of carboxylic acids; the Bronsted constant a'2 has a value of 0-60. The Hammett reaction constants Q2, Q'I and Q'2 have the same values as the respective aj, 0.2, c/\ and constants. The previous work of this series was concerned with the kinetics and mechanism of reactions of acetic acid, monochloro- and dichloroacetic acids with ethylene oxide catalysed with tertiary amines and carried out in alcohols as solvents^. In the work it was suggested that under the condi­ tions used ethylene oxide is consumed by both the acid-catalysed and parallel tert-amine-catalysed bimolecular nucleophilic substitution reactions. The reactions of ethylene oxide were accompanied by side reactions which especially in the case of the chloro-substitut ed acids led to formation of considerable amounts of by-products. This circumstance left some doubt concerning the validity of the kinetic dependences obtained for the whole region of conversions of the carboxylic acids. The results reported in the above-mentioned study allowed also to draw only qualitative conclusions about the relationship between the rate of the ethylene oxide reaction with carboxylic

Kinetics and mechanisms of polyesterifications II. Reactions of diacids with diepoxides

Abstract: This article is a critical review of most of the literature relative to non-catalyzed, base-catalyzed, and miscellaneous-catalyzed epoxy-carboxy esterifications and polyesterifications. Most kinetic data are relative to model esterifications; however, some polyesterification kinetics are analyzed. From the analysis of the results reported in the literature and found in our group it has been possible to compare and critize the various general mechanisms which have been proposed.

Specific features of the kinetics of addition esterification of epoxide with the carboxyl group

Abstract: The kinetics of addition esterification involving epoxide and carboxyl groups in the presence of a tertiary amine was investigated using a model system phenylglycidyl ether — caproic acid. It has been found that the reaction has an induction period. By means of IR spectra it has been proved that the equilibrium formation of catalytically active species (complex acid-amine) is the cause both of nonconstant values of experimentally determined reaction orders and of the occurrence of the induction period. The controversial experimental results reported in the literature are discussed.

The solvent effects in the reactions of carboxylic acids with oxiranes. 1. Kinetics of the reaction of acetic acid with epichlorohydrin in butan‐1‐ol

Abstract: Kinetics of the reaction of acetic acid with epichlorohydrin in the presence of chromium(III) acetate in butan-1-ol solution have been studied. The partial reaction orders with respect to reagents were found. The reactions were of first-order with respect to both epichlorohydrin and catalyst and zeroth order with respect to acetic acid. A kinetic model for the overall process has been proposed. The reaction constants have been calculated along with the activation parameters. The effect of dilution on the rate of addition is discussed. In the equimolar mixture of acetic acid and epichlorohydrin the apparent rate constant of the addition k1 initially decreases to increase again at the concentration of butan-1-ol exceeding 3 M. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 378–387, 2000

Catalytic activity of tertiary amines with antisymbatic change of basic and nucleophilic properties in the chloroxypropylation reaction of acetic acid

Abstract: The kinetic dependence of the reaction of (chloromethyl)oxirane ring-opening by acetic acid in the presence of tertiary amines R3N and RnNMe3−n has been studied. The orders of reaction with respect to acid and catalyst have been determined. The nucleophilicity of amines used has been measured in the quaternization reaction of R3N and RnNMe3−n by benzyl chloride (Menshutkin reaction). On the basis of correlations “amines structure–catalytic activity”, it has been shown that amines act as nucleophiles in this reaction.