REACTIONS OF ARYLSULPHONIC ESTERS: III. ON THE HYDROLYSIS OF METHYL p-METHYLBENZENESULPHONATE

1955 ◽  
Vol 33 (10) ◽  
pp. 1536-1543 ◽  
Author(s):  
R. E. Robertson
Keyword(s):  
Specific Heat ◽  
Temperature Dependence ◽  
Specific Solvation ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Reaction In Water

A study of the temperature dependence for the rate of hydrolysis of methyl p-methylbenzenesulphonate shows the specific heat of activation for this reaction in water to be 33.45 ± 3 cal./mole degree. A comparison with the corresponding term for other methyl compounds reveals differences apparently characteristic of the anionic portion of the molecule. These differences are discussed in terms of specific solvation.

Neutral Solvolysis of Acyl Carbon and the Temperature Dependence of the Kinetic Solvent Isotope Effect

1975 ◽  
Vol 53 (6) ◽  
pp. 869-877 ◽  
Author(s):  
B. Rossall ◽  
R. E. Robertson
Keyword(s):  
Temperature Dependence ◽  
Isotope Effect ◽  
Solvent Isotope Effect ◽  
Acyl Carbon ◽  
Rate Of Hydrolysis ◽  
Solvent Isotope ◽  
Neutral Conditions ◽  
Hydrolysis Of

The temperature dependence of the rate of hydrolysis of benzoic, phthalic, and succinic anhydrides have been determined in H2O and D2O under "neutral" conditions. Corresponding data have been obtained for methyl trifluoroacetate. While both series supposedly react by the same BAc2 mechanism, remarkable differences are made obvious by this investigation. Possible sources of such differences are proposed.

Studies in Solvolysis. Part VII. The Neutral Hydrolysis of Methyl Perchlorate

1975 ◽  
Vol 53 (20) ◽  
pp. 3106-3115 ◽  
Author(s):  
Ross Elmore Robertson ◽  
Adrianna Annesa ◽  
John Marshall William Scott
Keyword(s):  
Heat Capacity ◽  
Carbon Atom ◽  
Temperature Dependence ◽  
Thermodynamic Parameters ◽  
Isotope Effect ◽  
Perchlorate Ion ◽  
Rate Of Hydrolysis ◽  
Leaving Groups ◽  
Hydrolysis Of

The temperature dependence of the rate of hydrolysis of methyl perchlorate has been measured and the entropy (ΔS≠), enthalpy (ΔH≠), and heat capacity (ΔCp≠) of activation calculated. The measurements confirm that the perchlorate ion is superior to all other leaving groups in water. The isotope effect related to the hydrolysis of methyl-d3 perchlorate has been measured at three temperatures and shown to be inverse. The thermodynamic parameters and the isotope effect were examined with respect to the mechanism of substitution at a primary carbon atom.

Enzymatic reaction in water-in-oil microemulsions. Part 2.—Rate of hydrolysis of a hydrophobic substrate, 2-naphthyl acetate

1994 ◽  
Vol 90 (7) ◽  
pp. 979-986 ◽  
Author(s):  
Yoshikazu Miyake ◽  
Takuya Owari ◽  
Fumio Ishiga ◽  
Masaaki Teramoto
Keyword(s):  
Enzymatic Reaction ◽  
Hydrophobic Substrate ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Reaction In Water ◽  
Naphthyl Acetate

Hydrolysis of α-bromoisobutyrate ion in water

1967 ◽  
Vol 45 (18) ◽  
pp. 2071-2077 ◽  
Author(s):  
B. N. Hendy ◽  
W. A. Redmond ◽  
R. E. Robertson
Keyword(s):  
Temperature Dependence ◽  
Isotope Effect ◽  
Deuterium Isotope Effect ◽  
Detailed Mechanism ◽  
Temperature Range ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

The temperature dependence of the rate of hydrolysis of α-bromoisobutyrate ion in water was determined over a temperature range 9–37 °C. From these data corresponding values of ΔH≠, ΔS≠, and ΔCP≠ have been derived. The implication of these terms, together with corresponding data for hydrolysis in D2O and for the secondary deuterium isotope effect from the hydrolysis of (CD3)2CBrCOO−, provide a basis for reexamining the detailed mechanism with particular reference to accompanying solvent reorganization.

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.

Solvent reorganization for hydrolysis with hydrogen participation

1969 ◽  
Vol 47 (24) ◽  
pp. 4599-4605 ◽  
Author(s):  
Y. Inomoto ◽  
R. E. Robertson ◽  
G. Sarkis
Keyword(s):  
Acetic Acid ◽  
Isotope Effect ◽  
Activation Process ◽  
Solvent Isotope Effect ◽  
Butyl Bromide ◽  
Rate Of Hydrolysis ◽  
Solvent Isotope ◽  
Hydrolysis Of ◽  
Reaction In Water

A study of the rates of hydrolysis of 3-Me-2-butyl bromide and methanesulfonate in water leads to values of ΔCp≠ of −80 and −40 cal deg−1 mole−1, respectively. The product was about 85–95 % t-pentanol, the remainder being olefin. The value of ΔCp≠ for the solvolysis of the methanesulfonate in D2O was −44 cal deg−1 mole−1. The kinetic solvent isotope effect (k.s.i.e.) for the latter was unusually low (k.s.i.e. = 1.047 at 5 °C and 1.025 at 25 °C). Deuteration at C-3 led to a reduction in the rate of hydrolysis by a factor of about 2.25. This is consistent with an activation process involving "hydrogen participation" as previously reported by Winstein and Takahashi for solvolysis of the corresponding tosylate in acetic acid. In contrast to the latter work, the reaction in water appears to be uncomplicated.

Enzymatic reaction in water-in-oil microemulsions. Part 1.—Rate of hydrolysis of a hydrophilic substrate: acetylsalicylic acid

1993 ◽  
Vol 89 (12) ◽  
pp. 1993-1999 ◽  
Author(s):  
Yoshikazu Miyake ◽  
Takuya Owari ◽  
Kengo Matsuura ◽  
Masaaki Teramoto
Keyword(s):  
Acetylsalicylic Acid ◽  
Enzymatic Reaction ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Reaction In Water

Substituent Effects on the Micelle-Catalysed and Uncatalysed Basic Hydrolysis of a Series of Substituted N-Methyl-p-toluanilides

1979 ◽  
Vol 32 (8) ◽  
pp. 1717 ◽  
Author(s):  
TJ Broxton ◽  
NW Duddy
Keyword(s):  
Substituent Effects ◽  
Cationic Micelles ◽  
Mechanism Of Reaction ◽  
Rate Of Reaction ◽  
Hammett Correlation ◽  
Rate Of Hydrolysis ◽  
Linear Plot ◽  
Basic Hydrolysis ◽  
Hydrolysis Of ◽  
Reaction In Water

The rate of hydrolysis of a series of substituted N-methyl-p-toluanilides has been measured in water and in the presence of cationic micelles [cetyltrimethylammonium bromide (ctab)]. A Hammett correlation of the rates of hydrolysis gave a curved Hammett plot for the reaction in water (k2,W) but a linear plot for the rate of reaction at optimal concentrations of ctab (k2,max) and for derived rate constants within the micelle (k2,m) These results are discussed in terms of the mechanism of reaction, and for two compounds a micelle-induced change of 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.

The effect of polymeric and model imidazolium halides on the rate of hydrolysis of 4-acetoxy-3-nitrobenzoic acid

1985 ◽  
Vol 50 (4) ◽  
pp. 845-853 ◽  
Author(s):  
Miloslav Šorm ◽  
Miloslav Procházka ◽  
Jaroslav Kálal
Keyword(s):  
Catalyst Concentration ◽  
Low Molecular Weight ◽  
Imidazolium Chloride ◽  
First Order ◽  
Nitrobenzoic Acid ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Hydrolysis Of ◽  
Ethanol In Water ◽  
Direct Attack

The course of hydrolysis of an ester, 4-acetoxy-3-nitrobenzoic acid catalyzed with poly(1-methyl-3-allylimidazolium bromide) (IIa), poly[l-methyl-3-(2-propinyl)imidazolium chloride] (IIb) and poly[l-methyl-3-(2-methacryloyloxyethyl)imidazolium bromide] (IIc) in a 28.5% aqueous ethanol was investigated as a function of pH and compared with low-molecular weight models, viz., l-methyl-3-alkylimidazolium bromides (the alkyl group being methyl, propyl, and hexyl, resp). Polymers IIb, IIc possessed a higher activity at pH above 9, while the models were more active at a lower pH with a maximum at pH 7.67. The catalytic activity at the higher pH is attributed to an attack by the OH- group, while at the lower pH it is assigned to a direct attack of water on the substrate. The rate of hydrolysis of 4-acetoxy-3-nitrobenzoic acid is proportional to the catalyst concentration [IIc] and proceeds as a first-order reaction. The hydrolysis depends on the composition of the solvent and was highest at 28.5% (vol.) of ethanol in water. The hydrolysis of a neutral ester, 4-nitrophenyl acetate, was not accelerated by IIc.

Sign in / Sign up

Export Citation Format

Share Document