Hydrolysis acceleration

In the systems of Mo and Co sulfides, TAA was assumed to release sulfide ions by hydrolysis accelerated by hydrazine. Since the concentration of S2 in equilibrium with TAA is extremely low despite the exceedingly high release rate constant of S2- in the reversible reaction of Eq. (1), this assumption is reasonable if the concentrations of the free metal ions are too low for the nucleation of these metal sulfides. However, if the role of hydrazine is different than an accelerator of hydrolysis of TAA, and if the deposition rate of the metal sulfide monomers or the release rate of metal ions from the metal ion complexes such as orthomolybdate or cobalt... 

The amides are derived from oxazolidinones and yield "Z"-enolates with high stereoselectivity. The alkylating agent reacts in both cases from the side that is opposite to the side of the substituent highlighted in red. Alkaline hydrolysis accelerated by hydrogen peroxide proceeds with retention of configuration and yields enantiomerically pure a-alky-lated carboxylic acids X t and X 2 are the chiral amide groups. 

Alkaline hydrolysis accelerated by hydrogen peroxide proceeds with retention of configuration and yields... 

Two different types of enzymatic time-temperature integrators are described. The first, under the tradename of I-point, is based on a lipase-catalyzed hydrolysis reaction (125). The lipase is stored in a nonaqueous environment containing glycerol. The indicator contains two components that are mixed when the indicator is activated. The operating principle is as follows Upon activation, two volumes of reagents are mixed with each other. Lipase is thereby exposed to its substrate, here a triglyceride. At low temperatures there will be almost no hydrolytic reaction. As the temperature increases, hydrolysis accelerates and protons are liberated. A pH indicator is dissolved in the system. The indicator is selected to shift color after a certain amount of acid has been liberated by the enzyme-catalyzed process. Since the catalytic activity is influenced both by temperature and time, this indicator strip is said to be a time-temperature integrator. 

Pyrimidine nucleoside hydrolysis accelerated by bridging with 3, 5 -cyclic phosphate... 

Thus, the observed biodegradation of PHB showed coexistence of two different degradation mechanisms in hydrolysis in the polymer enzymatically or nonenzymatically catalyzed degradation. Although nonenzymati-cal catalysis occurred randomly in homopolymer, indicated by loss rate in PHB, at some point in a time, a critical molecular weight is reached whereupon enzyme-catalyzed hydrolysis accelerated degradation at the surface because easier enzyme/polymer interaction becomes possible. 

Constitution op Oils and Fats, and their Saponification. Researches of Chevreul and Berthelot—Mixed Glycerides—Modem Theories of Saponification—Hydrolysis accelerated by (1) Heat or Electricity, (2) Ferments, Castor-seed Ferment, Steapsin, Emul-sin, and (3) Chemical Reagents, Sulphuric Acid, Twitchell s Reagent, Hydrochloric Acid, Lime, Magnesia, Zinc Oxide, Soda and Potash. 

A full kinetic study of the hydrolysis of c-AMP (248) catalysed by Cu(II) terpyridine (Cutrpy) has revealed that the active species under alkaline conditions is the hydroxide form of the catalyst, (CutrpyOH)+. Although the same species acts as a base catalyst in the transesterification of RNA, here it behaves as a nucleophilic catalyst. Mechanistic studies of the hydrolysis of DNA and RNA by lanthanide ions have revealed that the catalytically active species are dinuclear hydroxo clusters. For example, the mechanism of the Ce(IV) catalysis of DNA hydrolysis (acceleration factor of lO -fold) is considered to involve the facilitated formation of a pentacoordinated intermediate (Scheme 45). However, the Ln(III) catalysis of RNA... 

ASA undergoes the normal reactions of acid anhydrides. Of particular interest in conjunction with sizing is the reaction with alcoholic hydroxy groups to yield an ester, and the hydrolysis with water. Both reactions occur in the papermaking system. ASA is highly reactive, and the reactions proceed rapidly and irreversibly. Although this would provide satisfactory development of sizing on a paper machine, the hydrolysis of ASA is undesirable. The hydrolysis accelerates with pH, time, and temperature and leads to deposits and runnabiHty problems on the paper machine. In order to Hmit the hydrolysis of ASA emulsions, the pH can be lowered immediately after the emulsification by addition of aluminum sulfate. 

The activation energy of the depurination of 19H was found to be 10 kcal/ mol by an Arrhenius plot, about 20kcal/mol lower than those (31-34 kcal/ mol) [79-81] of the depurination of DNAs in vitro and of hydrolysis of pyrimidines of deoxyribonucleosides. Due to the crowded environment around the hypoxanthine groups, the ground state potential energy of the W-glycosidic bond in the polymer was elevated more than that of the transition state, and thus the activation energy for the reaction decreased and the hydrolysis accelerated. 

Our compatriot N. A. Menshutkin made a great contribution to the development of the kinetics. In 1877 he studied in detail the reaction of formation and Iqrdrolysis of esters from various acids and alcohols and was the first to formulate the problem of the dependence of the reactivity of reactants on flieir chemical structure. Five years later when he studied the hydrolysis of tert-zmy acetate, he discovered and described the autocatalysis phenomenon (acetic acid formed in ester hydrolysis accelerates the hydrolysis). In 1887-, studying the formation of quaternary ammonium salts from amines and alkyl halides, he found a strong influence of the solvoit on the rate of this reaction (Menschutkin reaction) and stated the problem of studying the medium effect on the reaction rate in a solution. In 1888 N. A. Menschutkin introduced the term chmical kinetics in his monograph Outlines of Development of Chemical Views. ... 

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