Vinyl Carboxylic Acids Research Articles

Polymer Degradation Mechanism Reselection through Derivatization for Qualitative Pyrolysis Gas Chromatography Analysis

A poly(vinylcarboxylic acid) and its analogue alkyl ester exhibited significantly different thermal degradation mechanisms under pyrolysis conditions. The greatly enhanced monomer production of poly(alkylvinylcarboxylate) during pyrolysis makes possible qualitative analysis of poly(vinylcarboxylic acid) through its derivatized alkyl ester. In this study, copolymers containing poly(methacrylic acid) and methacrylic acid were used to demonstrate the pyrolysis gas chromatography qualitative analysis of derivatized polymer. The thermal decomposition mechanisms of poly(methacrylic acid), and poly(methyl methacrylate) were studied. The advantages and disadvantages of this derivatized process as related to Py-GC analysis are discussed.

ChemInform Abstract: Mechanistic Aspects of Ru(BINAP)‐Catalyzed Asymmetric Hydrogenation of Vinylcarboxylic Acid Derivatives

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Mechanistic aspects of Ru(BINAP)-catalysed asymmetric hydrogenation of vinylcarboxylic acid derivatives

The mechanism of the Ru II(BINAP)-catalysed hydrogenation of vinylcarboxylic acids has been investigated via detailed deuterium labelling studies. The activation of H 2 by the Ru catalyst was found to be via a heterolytic splitting route. The regioselectivity of the hydride migration step strongly correlates to the stability of the resulting metal-alkyl intermediate. When an α,β-unsaturated carboxylic acid such as 2-(6-methoxy-2-naphthyl)acrylic acid is used as the substrate, the hydrite migrates exclusively to the α position, forming a metal-primary alkyl intermediate. In the case of a β,γ-unsaturated carboxylic acid with an electron-withdrawing group attached to the β-carbon, the hydrite migrates exlusively to the γ-carbon, forming a five-membered ring metal-alkyl intermediate with the β-carbon coordinated to the metal. The product formation step involves two competing routes: the hydrogenolysis and the solvolysis of the metal-alkyl intermediates. The choice of each route is highly dependent on the reaction conditions. The solvolysis route is significant if the reaction is carried out under low H 2 pressure and the reaction medium is more acidic. Under high H 2 pressure, hydrogenolysis becomes the dominant route. Under basic conditions, the solvolysis route is essentially shut off and only the hydrogenolysis product is obtained. A unified mechanism which explains all of the known experimental results is proposed.

A facile insertion of carbon monoxide into C–Te bonds of organotellurium(II) and (IV) compounds leading to carboxylic acids

Treatment of some organotellurium(II) and (IV) compounds with CO in the presence of PdCl2 and LiCl gives aryl and vinylic carboxylic acids in good to high yields; in the case of (Z)-PhChCHTePh the major product was cis-cinnamic acid at 5–50 atm and the trans-isomer at 1 atm CO respectively.

Interaction of a 5-trans-vinylcarboxylic acid analogue of pyridoxal 5'-phosphate with apoaspartate aminotransferase. Covalent labeling of the enzyme.

The 5-trans-vinylcarboxylic acid analogue of pyridoxal 5'-phosphate has been prepared. Its pKa values were determined as 3.08, 4.10, and 7.33. The third pKa, that of the pyridinium nitrogen, is considerably lower than that of 8.2 observed for the corresponding saturated compound, 5'-carboxymethyl-5'-deoxypyridoxal. Absorption spectra of individual ionic forms have been resolved into component bands using lognormal distribution curves. The vinylcarboxylic acid analogue inactivates apoaspartate aminotransferase slowly at pH 8.3. An initial product absorbs at 26 kK (385 nm) and is converted slowly to a species with a narrow absorption band at 24.0 kK (417 nm). Meanwhile, the circular dichroism in the same region changes from positive to negative. At pH 5.2 the product abosrbs at 25.2 kK (397 nm). The 24.0-kK (417 nm) form is not reducible with sodium borohydride and the tightly bound chromophore is not released from the protein during denaturation by acid, base, or heat. L-Glutamate and erythro-beta-hydroxyaspartate both facilitate the formation of the 24.0-kK form. The reaction of the analogue with apoenzyme in the presence of erythro-beta-hydroxyaspartate is also accompanied by transient peaks, presumably representing quinonoid forms, at 19.0 kK (526 nm) and 20.3 kK (492 nm). The analogue reacts at basic pH with arginine, alpha-amino-gamma-guanidinobutyric acid, ornithine, cysteine, alpha, gamma-diaminobutyric acid, eh narrow absorption bands centered in the 24.0-24.4-kK (417-410 nm) region and resembling the product formed with the apoenzyme. Nuclear magnetic resonance and absorption spectroscopy indicate that the reaction with alpha- gamma-diaminobutyric acid proceeds via a hexahydropyrimidine derivative to a substituted tetrahydropyrimidine (a cyclic Schiff base) which is the final product. A similar reaction sequence with the apoenzyme is postulated and a structure with an unknown X group from the enzyme replacing the gamma-amino group of alpha, gamma-diaminobutyric acid is proposed for the 24.0-kK (417 nm) chromophore obtained with the apoenzyme. The proposed reactions are closely related to enzymatic and nonenzymatic reactions of pyridoxal 5'-sulfate (Yang, I. -Y., Khomutov, R. M., and Metzler, D. E. (1974), Biochemistry 13, 3877).

Vinyl oil monomers. I. Vicinal methacryloxy‐hydroxy soy oils

AbstractNew vinyl oil monomers have been prepared by combining epoxidized unsaturated oils with vinyl carboxylic acids. This is accomplished by heating the reactants in the presence of free radical inhibitors and appropriate reaction catalysts. The reaction consists of cleavage of the oxirane ring followed by addition of the vinyl acid through its carboxylic group. By varying the reactants and the conditions of reaction, a large family of related, but different, vinyl oil monomers can be prepared. Vicinal methacryloxy‐hydroxy soy oil monomers are clear, yellow, medium viscosity (2000–2500 cpoise), high molecular weight (1300–1500) liquids. Chemical analyses are presented for typical preparations. The monomers readily homopolymerize by a free radical mechanism to clear, solid, thermoset resins. They are compatible with a variety of commercial vinyl monomers and form copolymers which range from highly viscous liquids through soft gels, to tough rubbery products and hard resins. Data are presented on physical properties of copolymer castings of several specific vicinal methacryloxy‐hydroxy soy oil monomers.