Lanthanum ion catalysis of nucleophilic displacement reactions of monoesters of methyl phosphonic acid

1969 ◽  
Vol 47 (23) ◽  
pp. 4383-4387 ◽  
Author(s):  
R. J. Withey
Keyword(s):  
Aqueous Solution ◽  
Phosphonic Acid ◽  
Methylphosphonic Acid ◽  
Nucleophilic Displacement ◽  
Displacement Reactions ◽  
Lanthanum Ion ◽  
Rate Of Hydrolysis ◽  
Catalytic Effects ◽  
Hydrolysis Of

The catalytic effects of lanthanum ion on the rate of hydrolysis of p-nitrophenyl hydrogen methylphosphonate in aqueous solution at pH > 7.0 are reported. Increases in rate by a factor of about 3.6 × 104 have been observed. No such catalysis was found for diesters of methylphosphonic acid.

THE CHEMISTRY OF ETHYLENE OXIDE: V. THE REACTION OF ETHYLENE OXIDE WITH HALIDE IONS IN NEUTRAL AND ACID SOLUTION

1952 ◽  
Vol 30 (3) ◽  
pp. 169-176 ◽  
Author(s):  
A. M. Eastham ◽  
G. A. Latremouille
Keyword(s):  
Aqueous Solution ◽  
Ethylene Oxide ◽  
Acid Solution ◽  
Activation Energies ◽  
Hydrogen Halide ◽  
Halide Ions ◽  
Neutral Aqueous Solution ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Hydrolysis Of

The rates of reaction of halide ions with ethylene oxide in neutral aqueous solution and the rate of hydrolysis of ethylene oxide in acid solution have been measured and the activation energies determined. From these data and from the ratio of glycol to chlorohydrin formed when ethylene oxide reacts with excess aqueous hydrogen halide, the rates of the acid-catalyzed addition of halide ions to ethylene oxide at 25 °C. have been estimated.

Effect of Nε-Alkylation of the Substrate on the Hydrolysis of Benzoylglycyl-L-Lysine by Carboxypeptidase B

1975 ◽  
Vol 53 (11) ◽  
pp. 1145-1149 ◽  
Author(s):  
Graham J. Moore ◽  
N. Leo Benoiton
Keyword(s):  
Aqueous Solution ◽  
Steric Hindrance ◽  
Alkyl Group ◽  
Side Chain ◽  
Methyl Ethyl ◽  
Reductive Methylation ◽  
Carboxypeptidase B ◽  
Substrate Side ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

The action of carboxypeptidase B (EC 3.4.12.3) on the benzoylglycyl dipeptides Bz-Gly-Lys(X) where X = methyl, ethyl, propyl, formyl, dimethyl, isopropyl, trimethyl, and benzyl has been investigated. All were hydrolyzed, at a rate decreasing in the order indicated, except where X = trimethyl and benzyl. Compounds where X = dimethyl, formyl, and isopropyl were hydrolyzed very slowly, and did not inhibit the hydrolysis of Bz-Gly-Lys by the enzyme. The kinetic parameters kcat and Km were determined for compounds with X = methyl and ethyl. The observed decrease in rate of hydrolysis of substrates with increasing size of X is consistent with increasing steric hindrance effects arising from the interaction of the Nε-alkyl group with residues of the protein in the cleft which accommodates the substrate side-chain, and resulting in weaker binding of the substrate.Bz-Gly-Lys(Me2) was prepared by reductive methylation of Bz-Gly-Lys. Bz-Gly-Lys(Me3) was prepared by the reaction of Bz-Gly-Lys(Me2) with diazomethane in aqueous solution. Bz-Gly-Lys(Me) and Bz-Gly-Lys(Et) were synthesized by classical coupling procedures from the appropriately protected lysine derivatives.

REACTIONS OF SULPHONIC ESTERS: VI. THE TEMPERATURE DEPENDENCE OF THE RATE FOR THE HYDROLYSIS OF A SERIES OF ALKYL BENZENESULPHONATES

1957 ◽  
Vol 35 (7) ◽  
pp. 613-622 ◽  
Author(s):  
R. E. Robertson
Keyword(s):  
Transition State ◽  
Temperature Dependence ◽  
Methyl Ethyl ◽  
Temperature Dependent ◽  
Temperature Coefficients ◽  
Nucleophilic Displacement ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

Data are presented showing temperature dependence of the rate of hydrolysis of methyl, ethyl, isopropyl, and n-propyl benzenesulphonates in water. The heat of activation is shown to be temperature dependent to the extent of −30 to −40 cal./mole deg. Since, in solvolysis, the properties of water favor ionization over nucleophilic displacement, it is suggested that these temperature coefficients, ΔCp‡, and the accompanying entropy differences, ΔS‡, can be rationalized in terms of variations in the reorganization of the solvent about the transition state.

Kinetics of pyroarsenate hydrolysis in aqueous solution

1977 ◽  
Vol 30 (6) ◽  
pp. 1187 ◽  
Author(s):  
TG Richmond ◽  
JR Johnson ◽  
JO Edwards ◽  
PH Rieger
Keyword(s):  
Aqueous Solution ◽  
Rate Constant ◽  
Activation Parameters ◽  
Hydrolysis Rate ◽  
Associative Mechanism ◽  
Hydrolysis Rate Constant ◽  
Rate Of Hydrolysis ◽  
Ph Stat ◽  
Kinetics Of ◽  
Hydrolysis Of

The rate of hydrolysis of pyroarsenate in 0.1 mol dm-3 NaClO4 solutions, pH 6-9, was measured by a pH-stat technique at temperatures ranging from 278 to 298 K. The pKa of HAs2O73-, found to be the predominant reactant under these conditions, was 7.3 and 7.6 at 283 and 298 K, respectively. The hydrolysis rate constant for HAs2O73- was 0.05 s-1 at 298 K with activation parameters ΔH? = 49 � 9 kJ mol-1 and ΔS? = -107 � 30 J mol-1 K-1. An associative mechanism is indicated.

The Effects of Amines on the Esterase Activities of Thrombin and Thrombokinase and on Several Clotting Tests

1974 ◽  
Vol 31 (02) ◽  
pp. 309-318
Author(s):  
Phyllis S Roberts ◽  
Raphael M Ottenbrite ◽  
Patricia B Fleming ◽  
James Wigand
Keyword(s):  
Choline Chloride ◽  
Polymerization Process ◽  
Ammonium Bromide ◽  
Bovine Thrombin ◽  
One Stage ◽  
Human Proteins ◽  
Rate Of Hydrolysis ◽  
The One ◽  
Hydrolysis Of Esters ◽  
Hydrolysis Of

Summary1. Choline chloride, 0.1 M (in 0.25 M Tris. HCl buffer, pH 7.4 or 8.0, 37°), doubles the rate of hydrolysis of TAME by bovine thrombokinase but has no effect on the hydrolysis of this ester by either human or bovine thrombin. Only when 1.0 M or more choline chloride is present is the hydrolysis of BAME by thrombokinase or thrombin weakly inhibited. Evidence is presented that shows that these effects are due to the quaternary amine group.2. Tetramethyl ammonium bromide or chloride has about the same effects on the hydrolysis of esters by these enzymes as does choline chloride but tetra-ethyl, -n.propyl and -n.butyl ammonium bromides (0.1 M) are stronger accelerators of the thrombokinase-TAME reaction and they also accelerate, but to a lesser degree, the thrombin-TAME reaction. In addition, they inhibit the hydrolysis of BAME by both enzymes. Their effects on these reactions, however, do not follow any regular order. The tetraethyl compound is the strongest accelerator of the thrombokinase-TAME reaction but the tetra-ethyl and -butyl compounds are the strongest accelerators of the thrombin-TAME reaction. The ethyl and propyl compounds are the best (although weak) inhibitors of the thrombokinase-BAME and the propyl compound of the thrombin-BAME reactions.3. Tetra-methyl, -ethyl, -n.propyl and -n.butyl ammonium bromides (0.01 M) inhibit the clotting of fibrinogen by thrombin (bovine and human proteins) at pH 7.4, imidazole or pH 6.1, phosphate buffers and they also inhibit, but to a lesser degree, a modified one-stage prothrombin test. In all cases the inhibition increases regularly as the size of the alkyl group increases from methyl to butyl. Only the ethyl com pound (0.025 M but not 0.01 M), however, significantly inhibits the polymerization of bovine fibrin monomers. It was concluded that inhibition of the fibrinogen-thrombin and the one-stage tests by the quaternary amines is not due to any effect of the com pounds on the polymerization process but probably due to inhibition of thrombin’s action on fibrinogen by the quaternary amines.

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