Stanislav Ševčík

Conformational study of methylethers of the type CH3OCH2R: an NMR and vibrational spectroscopic study

Abstract Analysis of 13C NMR spectra of methylethers of the type CH3OCH2R, with R = CH3 (I), CH2CH3 (II), CH(CH3)2 (III) and C(CH3)3 (IV) has shown that the trans form strongly predominates on the OCH, bond, the gauche forms appearing only in those cases where close contact between methyl groups can be avoided. Analysis of both 1H and 13C NMR spectra indicates that all staggered forms are populated on the CH2R bond. In vibrational spectra, the strong Raman bands near 800 cm−1 were found to be very sensitive to conformational structure. For I, III and IV, the bands of various conformers in this range are separated, permitting ΔH to be determined.

Model compounds of hydrophilic polymers

SummaryFrom the products of hydrolysis of dimethyl 2-methoxymethyl-2, 4-dimethylglutarate, the pure stereoisomers of 2-methoxymethyl-2,4-dimethylglutaric acid and their anhydrides have been prepared. Alkaline hydrolysis of the stereoisomeric anhydrides yields the corresponding pure stereoisomeric acids which can be transformed to the corresponding pure threo- and erythrodimethyl esters by means of diazomethane. The configuration of the stereoisomeric anhydrides was determined by analysis of1H-NMR spectra, the configuration of the other compounds was derived from the anhydride structures based on the preparative procedure controlled by1H-NMR spectra.

The potentiometric behaviour of copolymers of methacrylic acid in water-ethanol solutions

SummaryThe synthesis is reported of copolymers of styrene with methacrylic acid and of methyl methacrylate with methacrylic acid by radical copolymerization, of copolymers of methyl methacrylate with methacrylic acid by partial alkaline hydrolysis of poly(methyl methacrylate), and of block copolymers of styrene with methacrylic acid. Modified titration curves of all these copolymers were recorded in water and water-ethanol solutions. In a solution containing 50 mass.% ethanol, only small differences could be observed between the potentiometric behaviour of the individual copolymers and polymethacrylic acid. Also, there were no essential differences in any of the solvents used between the potentiometric behaviour of block copolymers of styrene with methacrylic acid, on the one hand, and polymethacrylic acid, on the other. On the contrary, maxima and minima were always observed on the modified titration curves of statistical copolymers with a higher content of the hydrophobic comonomer in solutions with a high water content. Thus, using the modified titration curves, it is possible to decide whether a given copolymer is of the block or statistical type.

Precursors of hydrophilic polymers: 4a The kinetics of quaternization of poly (2-dimethylaminoethyl methacrylate) with methyl iodide

SummaryThe paper deals with a phenomenological description of the kinetics of quaternization of poly(2-dimethylaminoethyl methacrylates) (PDAEM) of various tacticity, brought about by methyl iodide at 11°C in water-ethanol solutions. At a low water content (below 43 mass %) in the mixed solvent the rate constant calculated by the integral method according to the second order increased with conversion of the reaction, while at a higher water content it decreased gradually from the originally high value. In a solvent containing 43 mass % water the rate constant of quaternization was almost independent of conversion, and from the kinetic viewpoint the polymer behaved as a low-molecular weight compound. In all solvents under investigation the isotactic polymer was more reactive than PDAEM having an atactic or syndiotactic structure. The reactivity of the polymers is compared with that of the low-molecular weight model compound, i.e. of 2-dimethylaminoethyl pivalate.