Reaction Of P-nitrophenyl Acetate Research Articles

Effect of medium on reactivity for alkaline hydrolysis of p-nitrophenyl acetate and S-p-nitrophenyl thioacetate in DMSO–H2O mixtures of varying compositions: ground state and transition state contributions

Second-order rate constants (kN) for reactions of p-nitrophenyl acetate (1) and S-p-nitrophenyl thioacetate (2) with OH– have been measured spectrophotometrically in DMSO–H2O mixtures of varying compositions at 25.0 ± 0.1 °C. The kN value increases from 11.6 to 32 800 M–1 s–1 for the reactions of 1 and from 5.90 to 190 000 M–1 s–1 for those of 2 as the reaction medium changes from H2O to 80 mol % DMSO, indicating that the effect of medium on reactivity is more remarkable for the reactions of 2 than for those of 1. Although 2 possesses a better leaving group than 1, the former is less reactive than the latter by a factor of 2 in H2O. This implies that expulsion of the leaving group is not advanced in the rate-determining transition state, i.e., the reactions of 1 and 2 with OH– proceed through a stepwise mechanism, in which expulsion of the leaving group from the addition intermediate occurs after the rate-determining step. Addition of DMSO to H2O would destabilize OH– through electronic repulsion between the anion and the negative-dipole end in DMSO. However, destabilization of OH– in the ground state is not solely responsible for the remarkably enhanced reactivity upon addition of DMSO to the medium. The effect of medium on reactivity has been dissected into the ground state and transition state contributions through combination of the kinetic data with the transfer enthalpies (ΔΔHtr) from H2O to DMSO–H2O mixtures for OH– ion.

DFT study on the effects of catalysis by β-cyclodextrin in the reaction of p-nitrophenyl acetate.

The reaction of p-nitrophenyl acetate and α-alanine can be improved apparently with β-cyclodextrin (β-CD) according to previous research, the interaction mechanism between β-cyclodextrin and p-nitrophenyl acetate is described in this paper. Density functional theory (DFT) method is used throughout the study. According to the energy (the binding energy, the deformation energy) and structural deformation, entry models and reaction process can be pinpointed, viz p-nitrophenyl acetate embed β-CD from the wide rim. Then frontier molecular orbital, dual descriptor, natural bonding orbital (NBO), and nuclear magnetic resonance (NMR) are employed to reveal the mechanism of electron transferring. The mechanism illustrates that β-CD plays a catalytic role during the synthesis reaction, improving the reactivity and selectivity of the process. Graphical Abstract DFT study on the effects of catalysis by β-cyclodextrin in the reaction of p-nitrophenyl acetate.

Catalytic properties of supramolecular systems based on polyoxyethylated calixarenes and amines

The rate of carboxylic ester cleavage by amphiphilic low-molecular-weight and polymeric amines in the presence of polyoxyethylated calix[4]arenes with different degrees of oxyethylation is determined by the formation of mixed aggregates, by the shift of pK a of the amine, and the character of the distribution of the reactants in functional micelles. All of the systems show a high substrate specificity. In the case of octyl- and decylamines, the reaction of p-nitrophenyl acetate is catalyzed and the reaction of more hydrophobic p-nitrophenyl laurate is inhibited. An opposite situation is observed in the systems based on branched polyethyleneimine: the reaction of p-nitrophenyl acetate is inhibited and the process involving p-nitrophenyl laurate is accelerated.

Kinetic Studies of Micelle - Assisted Reaction of p-Nitrophenyl Acetate with Benzo-Hydroxamate Ion in Water-Ethylene Glycol Mixtures

The pseudo-first order rate constant for the reaction of p-nitrophenyl acetate by benzohydroxamate ion was determined in water-ethylene glycol mixtures using cationic micellar solutions of alkyldimethyl and diethyl ethanol ammonium bromides. From the conductivity data of these surfactants in ethylene glycol, the critical micelle concentration (cmc), the micellar ionization degree (α), and Gibbs free energy of the micellization (ΔG 0 m ), have been determined. Addition of ethylene glycol in the micellar solutions results in an increase in the cmc and in an increase in micellar ionization degree. The dependence of observed rate constants were explained considering the structure of interfacial region, micellar aggregation number, water content in the micellar interfacial region and the equilibrium binding constants for the p-nitrophenyl acetate and benzohydroxamate ion to the micellar aggregates. The kinetic micellar effect was quantitatively explained by the pseudophase model.

Medium effects on the α-effect in DMSO–H2O mixtures — Comparative studies ofp-nitrophenyl benzoate and acetate — Dissection of ground-state and transition-state effects

In a study of the origin of the α-effect and its dependence on the nature of the reaction medium as well as structural effects, we report herein a kinetic study of the reactions of p-nitrophenyl benzoate (PNPB) with butan-2,3-dione monoximate (Ox–, α-nucleophile) and p-chlorophenoxide (p-ClPhO–, the reference nucleophile) in dimethyl sulfoxide (DMSO)–H2O mixtures of varying compositions at 25.0 ± 0.1 °C. The second-order rate constants (kN) decrease modestly on addition of DMSO to the medium up to 10 mol% DMSO but increase significantly beyond that point for both nucleophiles. Ox–is more reactive than p-ClPhO–in all solvent mixtures studied (i.e., the α-effect). The α-effect increases as the DMSO content in the medium increases up to 40 mol% DMSO and then decreases beyond that point resulting in a bell-shaped α-effect profile. The bell-shaped α-effect profile obtained for the current reaction is similar to that found previously for the corresponding reaction of p-nitrophenyl acetate (PNPA), differing notably however, in the magnitude of the α-effect beyond 40 mol% DMSO. The PNPB/p-ClPhO–reaction gains greater rate enhancement than the PNPA/p-ClPhO–reaction in the DMSO-rich region, resulting in the smaller α-effect for PNPB beyond 40 mol% DMSO. It is proposed that the observed modulation of the α-effect by the solvent medium is explicable as a ground-state effect in the H2O-rich region and a transition-state effect in the DMSO-rich region.Key words: medium effect, the α-effect, ground state, transition state, solvation, desolvation.

Molecular organization of reactants in the kinetics and catalysis of liquid phase reactions: IX. The catalytic assistance of an alcohol as a component of the medium in the aminolysis of esters

The kinetics of the reaction ofp-nitrophenyl acetate with n-butylamine is studied in various solvents containing n-butanol as a component of the medium. The alcohol is shown to assist the aminolysis by the participation in the proton transfer from the amine molecule to ester. The stoichiometric composition of the polymolecular complexes of amine with the alcohol participating in the reaction is found from the kinetic data at low concentrations of n-butanol and the data on its association in solutions. At high concentrations of the alcohol, the kinetic data are described within the framework of a model that assumes the participation in the reaction of hydroxy groups of the alcohol in the composition of alcohol clusters. The rate of the process is determined by the concentration and sizes of the clusters. The complex kinetics of the catalytic assistance of the alcohol as a component of the medium are quantitatively interpreted according to the concepts on the role of the structural organization of the liquid in the kinetics of molecular reactions in solutions.

Kinetics of the reactions of esters and primary amines in “oil-water” type microemulsions

The possibilities of using “oil-water” type microemulsions as a medium for reactions of nucleophilic substitution in esters have been considered. The kinetics of the reactions ofp-nitrophenyl acetate and caprylate with primary amines in the medium indicated has been studied. The hydrophoby factor, being of great importance for micellar solutions of surfactants, is not substantially manifested in detergent microemulsions: the rate constants of the reactions studied are in fact independent of the length of the alkyl radical of the nucleophile.

Catalysis by β-cyclodextrin in the reaction of p-nitrophenyl acetate with α-amino acids

The reactions of p-nitrophenyl acetate, 1, with both enantiomers of the following α-amino acids: alanine (2a), methionine (2b), leucine (2c), and tryptophan (2d), were studied in the presence of p-cyclodextrin (β-CD). All the reactions were catalyzed by β-CD and no chiral discrimination was observed. The reactions of 1 with the D isomers of 2a and 2d were also studied in the presence of α- and γ-CD. In both cases the catalysis increased in the order α < γ < β-CD. Also, to analyze the influence of the polar nature of the nucleophile, the reactions of 1 with both enantiomers of the methyl esters of 2a, 2c, and 2d were studied in the presence of β-CD. The catalysis observed was significantly smaller than that for the reactions with the amino acids. It is suggested that the catalysis by CDs is due to the formation of a ternary hydrogen-bonding complex that results from the association of the amino acid with the complexed substrate. The effect of the size of the CD cavity on the observed catalysis is attributed to the geometrical requirements for the reaction. The decrease in catalysis in the reactions with the methyl esters is due to a weaker hydrogen-bonding association with these neutral nucleophiles. Key words: cyclodextrins, catalysis, ester aminolysis.

ChemInform Abstract: Kinetic Study on the Reaction of p‐Nitrophenyl Acetate with 6‐Substituted 2,4‐Diamino‐1,3,5‐triazines

The reactions of p-nitrophenyl acetate (1) with six 6-substituted 2,4-diamino-1,3,5-triazines, (2a–2f), were kinetically investigated in aqueous DMSO or in water at 30 °C. It was found that the reaction rate R could be expressed according to the equation R=(k0+kN[2])[1], and that Bronsted-type plots for the kN-reaction give a straight line with a slope (β) of 1.05. The solvent deuterium isotope effect was not observed in this reaction [kN(H)⁄kN(D)=1.0–1.15]. Furthermore, the isolated reaction product was 2-acetylamino-4-amino-6-methyl-1,3,5-triazine (4c), which was formed by a nucleophilic attack of 2c to 1. From these results, the mechanism for this nucleophilic reaction is discussed.

The solvent effect on the α-effect

The reaction of p-nitrophenyl acetate with butane-2,3-dione monoximate anion as the α-nucleophile, compared with p-chlorophenoxide ion as the normal nucleophile, exhibits a maximum in rate enhancement (‘α-effect’) in dimethyl sulphoxide–water mixtures as the medium composition is varied.

The reactivity of p-nitrophenyl esters with surfactants in apolar solvents. VI. Structural effects on the reaction of p-nitrophenyl acetate with alkanediamine bis(dodecanoate) salts

The rate of decomposition of p-nitrophenyl acetate has been measured in benzene solutions of a series of alkane-α,ω-diamine bis(dodecanoate) salts. Me(CH2)10CO2-+NH3(CH2)NH3N+ -O2C(CH2)10ME(n=2-7,9,10,12) The micellar rate constant is affected by the diamine chain length, and the bimolecular rate constant is affected both by the chain length (and whether the number of carbon atoms is even or odd) and by the acidity of the diammonium head groups. The Br�nsted plot is linear but the slope in creases with increasing detergent concentration.

Esterolytic action of poly[p‐vinyl(thiophenol)‐co‐acrylic acid

AbstractHydrolyses of p‐nitrophenyl acetate (PNPA) and 3‐acetoxy‐N,N,N‐trimethylanilinium iodide (ANTI) catalyzed by poly[p‐vinyl(thiophenol)‐co‐acrylic acid] (PSH) were studied in the pH range of 8 – 9,5. The reaction of PNPA followed pseudo‐first‐order kinetics and was found to be catalyzed by the thiophenolate ions on the polymer backbone. In the case of positively charged ANTI, the rate of catalysis showed substrate saturation phenomena and could be described by a Michaelis‐Menten kinetics. This indicates that this reaction proceeds via a complex formed by electrostatic interaction between the substrate and the negatively charged polymer catalyst. When ionic strength was increased to 0,12 mol/l the reaction did not further follow the Michaelis‐Menten kinetics, suggesting that the complexation constant or the reaction rate of the complex might vary with the amount of the substrate incorporated in the polymer domain. Positively charged N,N,N‐trimethylanilinium iodide competively inhibited the PSH‐catalyzed hydrolysis of ANTI.

Differential effects of denaturing agents on acetylcholinesterase: Insensitivity of the reaction of methanesulfonyl fluoride compared to diisopropylphosphorofluoridate and p-nitrophenyl acetate

The effects of various agents that could be expected to perturb enzyme structure in a non-specific and reversible manner (alcohols, dimethylsulfoxide, dimethylformamide, dinitrobenzene, urea and guanidine · HCl) have been determined on reaction of acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) with a substrate, p-nitrophenyl acetate, and two irreversible inhibitors, diisopropylphosphorofluoridate and methanesulfonyl fluoride. In all three of these reactions an acyl group (acetyl, phosphoryl or sulfonyl respectively) bonds covalently with the active center of the enzyme. As expected, the reactions of p-nitrophenyl acetate and diisopropylphosphorofluoridate were severely retarded by most of these agents. By contrast, reaction of methanesulfonyl fluoride was usually depressed to a far smaller degree, and in two cases was faster. These findings are of interest in connection with: (1) differing requirements for the integrity of the active center in catalysis with various substrate analogs, and (2) the mechanism by which cationic substrate analogs accelerate reaction of the enzyme with methanesulfonyl fluoride.

Low-Temperatùre Kinetics in Protic Solvents. Reactions of p-Nitrophenyl Acetate in Methanol and Methanol-d at -78°

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTLow-Temperatùre Kinetics in Protic Solvents. Reactions of p-Nitrophenyl Acetate in Methanol and Methanol-d at -78°F. M. MengerCite this: J. Am. Chem. Soc. 1966, 88, 22, 5356–5357Publication Date (Print):November 1, 1966Publication History Published online1 May 2002Published inissue 1 November 1966https://doi.org/10.1021/ja00974a078RIGHTS & PERMISSIONSArticle Views51Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (262 KB) Get e-Alerts Get e-Alerts

The Reaction of p-Nitrophenyl Acetate with Thiols

<b>The Reaction of <b><i>p</i></b>-Nitrophenyl Acetate with Thiols</b>

Coördination Complexes and Catalytic Properties of Proteins and Related Substances. III. Effect of Zinc and Cupric Ions on the Reaction of p-Nitrophenyl Acetate with Glycylglycine1,2

Coördination Complexes and Catalytic Properties of Proteins and Related Substances. III. Effect of Zinc and Cupric Ions on the Reaction of p-Nitrophenyl Acetate with Glycylglycine^1,2