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Acid-catalyzed Hydrolysis (acid-catalyzed + hydrolysis)
Selected AbstractsHydrolysis of an isolable selenoseleninate under acidic and alkaline conditionsHETEROATOM CHEMISTRY, Issue 4 2001Akihiko Ishii Acid-catalyzed hydrolysis of a selenoseleninate [TripSe(O)SeTrip](Trip = 9-triptycyl) in 2 M HClO4 -1,4-dioxane at room temperature yielded the selenenic acid (TripSeOH). Alkaline hydrolysis of TripSe(O)SeTrip gave the diselenide (TripSeSeTrip) and the seleninic acid (TripSeO2H), where air oxidations of the resulting selenol (TripSeH) and TripSeOH occur at a considerable rate. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:198,203, 2001 [source] Acid-catalyzed hydrolysis of bridged bi- and tricyclic compounds.JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 9 20023-acetylnortricyclanes, Kinetics, XXXIX, mechanisms of the hydration reactions of 1- Abstract The disappearance of 1- and 3-acetylnortricyclanes (1-Ac and 2-Ac) in aqueous perchloric acid was followed by capillary gas chromatography at different temperatures and acid concentrations. 1-Ac is much less reactive than 2-Ac. The activation parameters, solvent deuterium isotope effects and parameters of excess acidity equations were measured and the products studied. 1-Acetylnortricyclane is hydrated according to the A -2 mechanism, i.e. the carbonyl oxygen is protonated in the fast pre-equilibrium and one water molecule attacks at the rate-limiting stage the partially open cyclopropane ring, producing 6-acetyl-2-norborneols. 3-Acetylnortricyclane is hydrated according to the AdE2 mechanism, i.e. the cyclopropane ring is slowly protonated and opened, with subsequent fast attack of water producing 3-, 5- and 7-acetyl-2-norborneols. Copyright © 2002 John Wiley & Sons, Ltd. [source] Acid-catalyzed hydrolysis of bridged bi- and tricyclic compounds.JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 12 20013-nortricyclanols, Kinetics, XXXVIII, mechanisms of 1- Abstract The disappearance of 1- and 3-nortricyclanols (1-OH and 2-OH) in aqueous perchloric acid was followed by capillary GC at different temperatures and acid concentrations. 1-OH is ca 1000 times more reactive than 2-OH. The activation parameters, solvent deuterium isotope effects and parameters of excess acidity equations were measured and the products were studied. Both isomeric nortricyclanols react according to the AdE2 mechanism, i.e. the cyclopropane ring is protonated at the rate-determining stage of the reaction. The protonation causes, in the case of 1-OH, an isomerization called homoketonization with 2-norbornanone as the only product and, in the case of 2-OH, hydration, i.e. the formation of hydroxyl-substituted norbornyl cations, the fast attack of which by water produces several norbornanediols. Copyright © 2001 John Wiley & Sons, Ltd. [source] Isergonic relationship in the acid-catalyzed hydrolysis of carboxylic esters with hydrogen-bonding capability,JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 6-7 2004Julio F. Mata-Segreda Abstract The average value of the enthalpies of activation for the acid-catalyzed hydrolyses of ethyl 2-hydroxypropanoate and five acetate esters with hydrogen bonding capability is 57±7,kJ,mol,1 (p,=,0.05). This value is 11,kJ,mol,1 lower than the mean observed for primary and secondary alkyl acetates and ethyl alkanoates, measured in water and in mixtures of water with organic solvent with high water content. The difference is attributed to tighter transition-state complex hydration via hydrogen bonding, relative to reactant ester species. Enthalpy,entropy compensation with an isokinetic temperature of 346,K was found to be valid at p<0.05, a value typical for solvent-mediated kinetic effects. Copyright © 2004 John Wiley & Sons, Ltd. [source] Kinetics and mechanism of acid-catalyzed hydrolysis of the diazo functional group of diazophenylacetamideJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 9 2003J. A. Chang Abstract The acid-catalyzed hydrolysis of diazophenylacetamide giving mandelamide as product was found to occur with a normal (kH/kD>1) hydronium ion isotope effect and to be subject to general acid rather than specific hydronium ion catalysis. This shows that the reaction occurs by rate-determining hydron transfer from the catalyzing acid to the diazo carbon atom of the substrate, followed by rapid displacement of the diazo group by water. Comparison of the rate of this reaction with those of the same process for other diazophenylacetic acid functional derivatives, PhCN2COX, reveals that the reactivity of these substrates is controlled by the electron-releasing resonance ability of the group X. Copyright © 2003 John Wiley & Sons, Ltd. [source] Computational chemistry study of the environmentally important acid-catalyzed hydrolysis of atrazine and related 2-chloro- s -triazinesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 8 2002Phillip Sawunyama Abstract Many chlorine-containing pesticides, for example 2-chloro- s -triazines, are of great concern both environmentally and toxicologically. As a result, ascertaining or predicting the fate and transport of these compounds in soils and water is of current interest. Transformation pathways for 2-chloro- s -triazines in the environment include dealkylation, dechlorination (hydrolysis), and ring cleavage. This study explored the feasibility of using computational chemistry, specifically the hybrid density functional theory method, B3LYP, to predict hydrolysis trends of atrazine (2-chloro- N4 -ethyl- N6 -isopropyl-1,3,5-triazine-2,4-diamine) and related 2-chloro- s -triazines to the corresponding 2-hydroxy- s -triazines. Gas-phase energetics are described on the basis of calculations performed at the B3LYP/6-311++G(d,p)//B3LYP/6-31G* level of theory. Calculated free energies of hydrolysis (,hG298) are nearly the same for simazine (2-chloro- N4,N6 -diethyl-1,3,5-triazine-2,4-diamine), atrazine, and propazine (2-chloro- N4,N6 -di-isopropyl-1,3,5-triazine-2,4-diamine), suggesting that hydrolysis is not significantly affected by the side-chain amine-nitrogen alkyl substituents. High-energy barriers also suggest that the reactions are not likely to be observed in the gas phase. Aqueous solvation effects were examined by means of self-consistent reaction field methods (SCRF). Molecular structures were optimized at the B3LYP/6-31G* level using the Onsager model, and solvation energies were calculated at the B3LYP/6-311++G(d,p) level using the isodensity surface polarizable continuum model (IPCM). Although the extent of solvent stabilization was greater for cationic species than neutral ones, the full extent of solvation is underestimated, especially for the transition state structures. As a consequence, the calculated hydrolysis barrier for protonated atrazine is exaggerated compared with the experimentally determined one. Overall, the hydrolysis reactions follow a concerted nucleophilic aromatic substitution (SNAr) pathway. Published in 2002 for SCI by John Wiley & Sons, Ltd [source] | ||||||||||