150-76-5Relevant articles and documents
Description of Solvent Dependence of Rate Constants in Terms of Pairwise Group Gibbs Function Interaction Parameters. Medium Effects for Hydrolysis of p-Methoxyphenyl Dichloroacetate in Aqueous Solutions Containing Urea and Alkyl-Substituted Ureas
Blokzijl, Wilfried,Engberts, Jan B. F. N.,Jager, Jan,Blandamer, Michael J.
, p. 6022 - 6027 (1987)
Rate constants for neutral hydrolysis of p-methoxyphenyl dichloroacetate in aqueous solutions are sensitive to the molarity of added urea and alkyl-substituted ureas.These dependences are considered in the light of pairwise Gibbs function parameters describing interaction between solutes in aqueous solutions.In the next stage these interactions are examined by using the Savage-Wood additivity principle for pairwise group interaction parameters involving organic solutes and both initial and transition states for the hydrolysis reaction.The basis of the approach is described showing how kinetic and thermodynamic data are drawn together and used to comment on mechanisms of reaction in aqueous solutions.For the hydrolysis of the dichloroacetate ester, we account for the observed dependence of rate constant on solvent in terms of a reaction that is second order with respect to water, where the transition state exposes three OH groups to the aqueous solution, and in terms of derived group interaction parameters involving these OH groups and both CH2 and CONH groups in added solutes.
Inhibition of Water-Catalyzed Ester Hydrilysis in Hydrophobic Microdomains of Poly(methacrylic acid) Hypercoils
Jager, Jan,Engberts, Jan B. F. N.
, p. 3331 - 3334 (1984)
The water-catalyzed hydrolysis of p-methoxyphenyl dichloroacetate (1) and 2,2-dichloropropionate (2) in aqueous solution at 25 deg C is strongly retarded by neutral atactic (at) and syndiotactic (st) poly(methacrylic acid) (PMAA), but not by poly(acrylic acid) and poly(N-vinylpyrrolidone).The rates and thermodynamic activation parameters are consistent with binding of the substrates to hydrophobic microdomains within the PMAA hypercoil.A conformational transition of PMAA to an extended coil leads to disappearance of the rate inhibition.This transition is induced either by ionization of PMAA or, at constant pH (ca. 3), by addition of urea and can be monitored by potentiometric titrations.Solubility measurements employing the water-insoluble dye Orange OT further established hydrophobic bonding to neutral at-PMAA.Whereas inhibition of the hydrolysis of 1 and 2 in water in the presence of hydrophobic cosolvents or micelles is characterized by initial-state stabilization, it appears that the inhibition by at- and st-PMAA primarily involves destabilization of the transition state.The effect of PMAA may be explained in terms of a lack of water penetration into the hydrophobic microdomains.
Kinetics of hydrolysis of 4-methoxyphenyl-2,2-dichloroethanoate in binary water-cosolvent mixtures; the role of solvent activity and solute-solute interactions
Rispens, Theo,Cabaleiro-Lago, Celia,Engberts, Jan B. F. N.
, p. 597 - 602 (2005)
Rate constants are reported for the pH-independent hydrolysis of 4-methoxyphenyl-2,2-dichloroethanoate in aqueous solution as a function of the concentration of added cyanomethane (acetonitrile), polyethylene glycol (PEG 400) and tetrahydrofuran (THF). The concentration of water was varied between ca. 25 and 55.5 M. It was found that the variation in water activity yields only a minor contribution to the observed variation in rate constants. Interestingly, for both cyanomethane and PEG 400 log(k) varies approximately linearly with the molar concentration of water. Medium effects in highly aqueous solutions ([H2O] > 50 M) of ethanol, 1-propanol, 2-propanol, 1-butanol and 2-methyl-2-propanol have also been determined. Unexpectedly, in this concentration range the alcohols induce significantly smaller effects per unit volume than cyanomethane. The present results are discussed in terms of pairwise interaction parameters. Isobaric activation parameters have been determined and reveal remarkable differences in the nature of the induced medium effects.
The mechanism of hydrolysis of aryl ether derivatives of 3-hydroxymethyltriazenes
Carvalho, Emilia,Francisco, Ana Paula,Iley, Jim,Rosa, Eduarda
, p. 2056 - 2063 (2005)
1-Aryl-3-aryloxymethyl-3-methyltriazenes hydrolyse to the corresponding anilines and phenols by specific-acid-catalysed, general-acid-catalysed and pH-independent mechanisms. All compounds studied exhibit specific- and general acid catalysis, though for 5a general acid catalysis was not observed below a pH of approximately 4, while for compounds 5e,f, such catalysis was absent above a pH of approximately 5. The pH-independent pathway is observed only for those compounds, 5d-f, that contain good aryloxy nucleo-fugic groups. The specific-acid-catalysed pathway is supported by a solvent deuterium isotope effect (SDIE) of 0.64, consistent with a mechanism involving protonation of the substrate followed by rate-determining unimolecular decomposition of the protonated species. The kH+ values gave rise to a Hammett p value of -0.93, reflecting the competing effect of the substituents on the protonation of the substrate and the cleavage of the aryl ether. Correlation of k H+ with the pKa of the phenol leaving group affords a β1g of 0.3. Decomposi tion of the protonated intermediate proceeds via a triazenyliminium ion that can be trapped by methanol. The general-acid-catalysed process exhibits an SDIE of 1.43 and Hammett p values of 0.49, 0.84 and 1.0 for reactions catalysed by chloroacetic, formic and acetic acids, respectively. Correlation of KA with the pKa of the acid gave Bronsted a values that diminish from 0.6 for O-aryl systems that are poor nucleofuges (5a, b) to 0.2 for the best nucleofuge (5f), reflecting the different extents of proton transfer required to expel each phenol. Compounds containing powerful nucleofuges exhibit a pH-independent reaction that has an SDIE of 1.1, a Hammett p value of 3.4 and a Bronsted β1g value of 1.4. These imply a mechanism involving displacement of the aryloxide leaving group to form a triazenyliminium ion intermediate that again was trapped as a methyl ether. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).
Novel photo-fragmentation of 3,3,6,6-tetra(p-methoxyphenyl)-1,2-dioxane through a C-O bond cleaved 1,6-diradical intermediate
Kamata, Masaki,Tanaka, Takehito,Kato, Mitsuaki
, p. 8181 - 8184 (1996)
Photolysis and thermolysis of 3,3,6,6-tetraaryl-1,2-dioxanes were investigated. The photolysis of 3,3,6,6-tetra(p-methoxyphenyl)-1,2-dioxane afforded 1,4,4-tri(p-methoxyphenyl)-3-buten-1-one and p-methoxyphenol through a novel C-O bond cleaved 1,6-diradical intermediate, while the thermolysis mainly afforded the expected decomposition product 4,4'-dimethoxybenzophenone through an O-O bond cleaved 1,6-dioxy diradical intermediate.
Gold nanoparticles stabilized by graphene quantum dots as catalysts for C–C bond cleavage in β-O-4 lignin model compounds
Zhang, Fangwei,Zhang, Jiali,Guo, Shouwu
, p. 105 - 109 (2019)
In this work, we report oxidative cleavage of C–C bonds in β-O-4 lignin models that is catalyzed by gold nanoparticles stabilized by graphene quantum dots (AuNPs-GQDs). We demonstrate that GQDs can enhance the catalytic activity of AuNPs. The AuNPs-GQDs shows the highest catalytic activity when the mass ratio of AuNPs to GQDs is of 1:18. Moreover, AuNPs-GQDs exhibits higher activity in the cleavage of Cα–Cβ bond of the compounds when their Cβ is adjacent to an oxygen atom. The possible oxidation pathway is proposed.
Efficiency of 2.45 and 5.80 GHz microwave irradiation for a hydrolysis reaction by thermostable β-Glucosidase HT1
Nagashima, Izuru,Sugiyama, Jun-Ichi,Sakuta, Tomomi,Sasaki, Masahide,Shimizu, Hiroki
, p. 758 - 760 (2014)
Microwave irradiation at different frequencies gave unique results for the hydrolyses of glycosyl bonds by β-Glucosidase HT1. With the observed relative complex permittivity data for the reaction buffer, 2.45 GHz microwave radiation affected both waters and ions, while 5.80 GHz only affected waters. We, here, propose that would be one of the unique "microwave nonthermal effects".
Isobaric and Isochoric Activation Parameters for the Water-Catalyzed Hydrolysis of p-Methoxyphenyl 2,2-Dichloropropionate in Typically Aqueous Solutions
Holterman, Herman A. J.,Engberts, Jan B. F. N.
, p. 6382 - 6384 (1982)
Isobaric thermodynamic activation parameters (ΔGp, ΔHp, ΔSp) and volumes of activation (ΔV) have been measured for the water-catalyzed hydrolysis of p-methoxyphenyl 2,2-dichloropropionate (1) in water and in t-BuOH-H2O (nH2O = 0.950 and 0.925) and 2-n-butoxyethanol-H2O (nH2O = 0.980) at 25 deg C.These data, in combination with the isobaric thermal expansivities (α) and the isothermal compressibilities (β) of the solvent, were used to calculate the isochoric activation parameters ΔUv and ΔSv.It is found that the solvent dependence of the sets (ΔHp, ΔSp) and (ΔUv, ΔSv) is widely different as a result of the large changes in α/β and in ΔV.The results are interpreted mainly in terms of hydrophobic interactions between 1 and the organic cosolvent and the large electrostriction, as expressed in the strongly negative ΔV values.The analysis is facilitated by consideration of thermodynamic parameters for transfer of a model substrate (p-nitrophenyl propionate) from water to the t-BuOH-H2O system.It is concluded that both isobaric and isochoric activation parameters contain fundamental information about the solvation changes during the activation process.There is no compelling evidence to prefer either of these sets for an analysis of kinetic solvent effects on the hydrolysis of 1 in the solvent systems used.
Origins of high catalyst loading in copper(i)-catalysed Ullmann-Goldberg C-N coupling reactions
Sherborne, Grant J.,Adomeit, Sven,Menzel, Robert,Rabeah, Jabor,Brückner, Angelika,Fielding, Mark R.,Willans, Charlotte E.,Nguyen, Bao N.
, p. 7203 - 7210 (2017)
A mechanistic investigation of Ullmann-Goldberg reactions using soluble and partially soluble bases led to the identification of various pathways for catalyst deactivation through (i) product inhibition with amine products, (ii) by-product inhibition with inorganic halide salts, and (iii) ligand exchange by soluble carboxylate bases. The reactions using partially soluble inorganic bases showed variable induction periods, which are responsible for the reproducibility issues in these reactions. Surprisingly, more finely milled Cs2CO3 resulted in a longer induction period due to the higher concentration of the deprotonated amine/amide, leading to suppressed catalytic activity. These results have significant implications on future ligand development for the Ullmann-Goldberg reaction and on the solid form of the inorganic base as an important variable with mechanistic ramifications in many catalytic reactions.
Aryldiazonium Salts as Photo-affinity Labelling Reagents for Proteins
Kieffer, Brigitte L.,Goeldner, Maurice Ph.,Hirth, Christian G.
, p. 398 - 399 (1981)
Aryldiazonium tetrafluoroborates, substituted in the para-position by electron donating substituents, are potential photo-affinity labelling reagents for proteins and after light activation irreversibly inhibit acetylcholinesterase; using radiolabelled reagent, the inactivation is shown to be approximately stoicheiometric.
