Kinetic acrylic acid derivatives

Quantitative rate measurements under a variety of conditions support such a mechanism [4, 15]. A complete kinetic analysis is available for the hydrogenation of acrylic acid derivatives using the precatalysts RuCl2(PPh3)3 in the solvent dimethylacetamide, although the system is much less active in this more polar and coordinating solvent (e.g., entry 3, Table 3.1). 

Seki and Tirrell [436] studied the pH-dependent complexation of poly(acrylic acid) derivatives with phospholipid vesicle membranes. These authors found that polyfacrylic acid), poly(methacrylic arid) and poly(ethacrylic acid) modify the properties of a phospholipid vesicle membrane. At or below a critical pH the polymers complex with the membrane, resulting in broadening of the melting transition. The value of the critical pH depends on the chemical structure and tacticity of the polymer and increases with polymer hydro-phobicity from approximately 4.6 for poly(acrylic acid) to approximately 8 for poly(ethacrylic acid). Subsequent photophysical and calorimetric experiments [437] and kinetic studies [398] support the hypothesis that these transitions are caused by pH dependent adsorption of hydrophobic polymeric carboxylic acids... 

Scheme5.37. Preferred sites of vinylic deprotonation of acrylic acid derivatives[329, 337] and pyrimidinediones[341-343]. kin kinetically favored therm thermodynamically favored.

The fact that the rate of some Diels-Alder [4 + 2] cycloaddition reactions is affected, albeit only slightly, by the solvent was used by Berson et al. [52] in establishing an empirical polarity parameter called Q. These authors found that, in the Diels-Alder addition of cyclopentadiene to methyl acrylate, the ratio of the endo product to the exo product depends on the reaction solvent. The endo addition is favoured with increasing solvent polarity cf. Eq. (5-43) in Section 5.3.3. Later on, Pritzkow et al. [53] found that not only the endojexo product ratio but also the absolute rate of the Diels-Alder addition of cyclopentadiene to acrylic acid derivatives increases slightly with increasing solvent polarity. The reasons for this behaviour have already been discussed in Section 5.3.3. Since reaction (5-43) is kinetically controlled, the product ratio [endo]l[exo] equals the ratio of the specific rate constants, and Berson et al. [52] define... 

The amide group is readily hydrolyzed to acrylic acid, and this reaction is kinetically faster in base than in acid solutions (5,32,33). However, hydrolysis of N-alkyl derivatives proceeds at slower rates. The presence of an electron-with-drawing group on nitrogen not only facilitates hydrolysis but also affects the polymerization behavior of these derivatives (34,35). With concentrated sulfuric acid, acrylamide forms acrylamide sulfate salt, the intermediate of the former sulfuric acid process for producing acrylamide commercially. Further reaction of the salt with alcohols produces acrylate esters (5). In strongly alkaline anhydrous solutions a potassium salt can be formed by reaction with potassium / /-butoxide in tert-huty alcohol at room temperature (36). 

Abstract. Auto-accelerated polymerization is known to occur in viscous reaction media ("gel-effect") and also when the polymer precipitates as it forms. It is generally assumed that the cause of auto-acceleration is the arising of non-steady-state kinetics created by a diffusion controlled termination step. Recent work has shown that the polymerization of acrylic acid in bulk and in solution proceeds under steady or auto-accelered conditions irrespective of the precipitation of the polymer. On the other hand, a close correlation is established between auto-acceleration and the type of H-bonded molecular association involving acrylic acid in the system. On the basis of numerous data it is concluded that auto-acceleration is determined by the formation of an oriented monomer-polymer association complex which favors an ultra-fast propagation process. Similar conclusions are derived for the polymerization of methacrylic acid and acrylonitrile based on studies of polymerization kinetics in bulk and in solution and on evidence of molecular associations. In the case of acrylonitrile a dipole-dipole complex involving the nitrile groups is assumed to be responsible for the observed auto-acceleration. 

When the polymer is charged, the repulsive forces of the charges prevent an approach of the radicals, and the lifetime of the radicals increases dramatically. In the case of poly(acrylic acid), for example, the decay of the poly(acrylic) acid radicals is fast and follows the same kinetics as any radical derived from neutral polymers as long as the polymer is fully protonated (low pH) (Ulanski et al. 1996c). With increasing pH and concomitant dissociation of the polymer, however, the polymer assumes a rod-like shape, its segments become less flexible, and repulsive forces increasingly prevent their approach. Some radicals survive even for hours under such conditions. 

The various data obtained for the kinetics of graft copolymerization onto PTFE films demonstrate that this reaction is complicated by the fact that the rate of diffusion of the monomer may become the controlling factor. It seems interesting at this point to compare and discuss together the results obtained with the different monomers. Table I summarizes the data obtained for autoacceleration indexes (/ ), dose-rate exponents (a), and over-all activation energies E, with styrene, acrylic acid, and vinylpyridine. Several conclusions can be derived from an examination of these data. 

Reactives of Side-Chains of Monocyclic Thiophens. - The rate constants for the esterification of some 3-, 4-, and 5-substituted thiophen-2-carboxylic acids and of some 2- and 4-substituted thiophen-3-carboxylic acids with diazodiphenylmethane in methanol solution have been measured, and linear correlations gave information about the transmission of substituent effects. The rates of alkaline hydrolysis of ethyl thiophen-2-carboxylate in ethanol-water and DMSO-water media have been measured and compared with those of other heterocyclic esters. The kinetics of iodination of 2-acetylthiophen in methanol-water, using different carboxylate buffers, have been studied.Basicity constants have been measured for j3-(2-thienyl)-acrylamides and compared with those of the corresponding benzene and furan derivatives. The acidity constants of ( )-a-phenyl-j3-(2-thienyl)-acrylic acids and analogous furan-, selenophen-, and pyridine-substituted compounds have been measured, and have been rationalized by an equation involving separate contributions of polar, conjugative, and steric effects of the heterocycles. ... 

Irradiation of 2-[N-(pentafluorophenyI)amino]-3-phenylcyclopropenone promotes decarbonylation to give N-(pentafluorophenyl)phenylethynamine and 2-phenyl-3-[N-(pentafluorophenyl)amino]acrylic acid by a process for which there is no known precedent,and the photoextrusion of carbon monoxide from l,3-bis(ethylenedioxy)indan-2-one has been used as the first step in a new synthesis of 1,2-dioxobenzocyclobutene. This represents an unusual example of the decarbonylation of a five-membered cyclic ketone in the preparation of a highly strained and functionalised cyclobutane derivative. The photolysis of a-naphthaleneacetic acid in aqueous solution proceeds by decarboxylation and oxidation of the aromatic ring, and has been carried out at a variety of different wavelengths. The primary step occurs by pseudo-first order kinetics and the optimum photolysis rate has been observed using Ti02 as photocatalyst. Within the cavity of P-cyclodextrin, naproxene (129) has been photodecarboxylated to... 

It is noteworthy that a basic assumption made in the derivation of the free radical desorption rate constant is that the adsorbed layer of surfactant or stabilizer surrounding the particle does not act as a barrier against the molecular diffusion of free radicals out of the particle. Nevertheless, a significant reduction (one order of magnitude) in the free radical desorption rate constant can happen in the emulsion polymerization of styrene stabilized by a polymeric surfactant [42]. This can be attributed to the steric barrier established by the adsorbed polymeric surfactant molecules on the particle surface, which retards the desorption of free radicals out of the particle. Coen et al. [70] studied the reaction kinetics of the seeded emulsion polymerization of styrene. The polystyrene seed latex particles were stabilized by the anionic random copolymer of styrene and acrylic acid. For reference, the polystyrene seed latex particles stabilized by a conventional anionic surfactant were also included in this study. The electrosteric effect of the latex particle surface layer containing the polyelectrolyte is the greatly reduced rate of desorption of free radicals out of the particle as compared to the counterpart associated with a simple... 

Xanthenyliumsodium (from sodamide and xanthene) reacts with aziridines to give a mixture of 9-mono- (271) or 9,9-di-substituted xanthenes (272).Addition of perchloric acid to unsymmetric allenes such as the 9-xanthylidene derivative (273) (prepared by a new route from 9,9-dichloroxanthene and an alkene) gave a red xanthylium salt (274), which was converted into a colourless spiro-indene (275) on heating.Full details have now been published of the properties and of the reactions of 9-diazoxanthene (276) and 9-xanthylidene (278) with methyl acrylate, substituted styrenes, several ketones, and alkyl-benzenes. The kinetics of the reaction with styrenes were studied and the conversion of (276) into (278) was achieved by photolysis of the tosylhydrazone (277) at —25 °C. 

Abstract The in vitro enzyme-mediated polymerization of vinyl monomers is reviewed with a scope covering enzymatic polymerization of vitamin C functionalized vinyl monomers, styrene, derivatives of styrene, acrylates, and acrylamide in water and water-miscible cosolvents. Vitamin C functionalized polymers were synthesized via a two-step biocatalytic approach where vitamin C was first regioselectively coupled to vinyl monomers and then subsequently polymerized. The analysis of this enzymatic cascade approach to functionalized vinyl polymers showed that the vitamin C in polymeric form retained its antioxidant property. Kinetic and mechanistic studies revealed that a ternary system (horseradish peroxidase, H2O2, initiator fS-diketone) was required for efficient polymerization and that the initiator controls the characteristics of the polymer. The main attributes of enzymatic approaches to vinyl polymerization when compared with more traditional synthetic approaches include facile ambient reaction environments of temperature and pressure, aqueous conditions, and direct control of selectivity to generate functionalized materials as described for the ascorbic acid modified polymers. 

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