SOLVOLYSIS IN DEUTERIUM AND HYDROGEN OXIDE

1956 ◽  
Vol 34 (12) ◽  
pp. 1714-1718 ◽  
Author(s):  
P. M. Laughton ◽  
R. E. Robertson
Keyword(s):  
Heavy Water ◽  
Rate Ratio ◽  
Methyl Chloride ◽  
Rate Data ◽  
Methyl Ethyl ◽  
Butyl Chloride ◽  
Initial States ◽  
The Difference ◽  
Hydrogen Oxide ◽  
Hydrolysis Of

Rate data for a series of benzenesulphonates, halides, and methyl methanesulphonate were determined in light and heavy water. The rate ratio [Formula: see text] varied with the nature of the anion being formed from 0.94. for the hydrolysis of methyl methanesulphonate to 0.78 for methyl chloride. This difference in ratio was attributed to differences in the nature of the solvation of the initial states. No appreciable differences arose, however, through the alkyl series methyl, ethyl, isopropyl benzenesulphonates, and the difference for the ratio [Formula: see text] between MeCl and t-butyl chloride was small, contrary to recently published work.

Studies in solvolysis. Part I. The neutral hydrolysis of some alkyl trifluoroacetates in water and deuterium oxide

1968 ◽  
Vol 46 (18) ◽  
pp. 2887-2894 ◽  
Author(s):  
June G. Winter ◽  
J. M. W. Scott
Keyword(s):  
Deuterium Oxide ◽  
Isotope Effects ◽  
Activation Process ◽  
Rate Data ◽  
Methyl Ethyl ◽  
Light Water ◽  
Carbonium Ion ◽  
Solvent Isotope ◽  
Hydrolysis Of ◽  
Solvent Isotope Effects

The temperature dependence of the rates of neutral hydrolysis of a series of alkyl trifluoroacetates (CF3COOR; R = methyl, ethyl, s-propyl, t-butyl) has been determined in both light and heavy water. From these studies the thermodynamic parameters (ΔH≠, ΔS≠) which characterize the activation process have been calculated. Sufficient rate data have been obtained in the case of the ethyl ester to calculate the heat capacity of activation (ΔCP≠) for the hydrolysis of this compound in light water. Both the entropies and enthalpies of activation as well as the solvent isotope effects are consistent with the proposal that the primary and secondary esters react by an acyl–oxygen BAc2 mechanism, in contrast to the tertiary ester, which appears to react either by a carbonium ion (SN1) process or by a route which combines both the BAc2 and SN1 paths.

THE HYDROLYSIS OF SUBSTITUTED METHYL BENZENESULFONATES IN WATER

1966 ◽  
Vol 44 (6) ◽  
pp. 685-688 ◽  
Author(s):  
R. E. Robertson ◽  
A. Stein ◽  
S. E. Sugamori
Keyword(s):  
Negligible Effect ◽  
Rate Data ◽  
The Difference ◽  
Hydrolysis Of

Rate data and derived parameters for the hydrolysis of a series of para-substituted methyl benzenesulfonates are given. The introduction of such substituents has negligible effect on ΔCp≠, and the difference in rate is largely reflected in δXΔS≠.

THE HYDROLYSIS OF A SERIES OF STRAIGHT-CHAIN ALKYL METHANESULPHONIC ESTERS IN WATER

1961 ◽  
Vol 39 (4) ◽  
pp. 881-888 ◽  
Author(s):  
P. W. C. Barnard ◽  
R. E. Robertson
Keyword(s):  
Heat Capacity ◽  
Activation Process ◽  
Rate Data ◽  
Methyl Ethyl ◽  
Straight Chain ◽  
Hydrolysis Of

Rate data for the hydrolysis of methyl, ethyl, n-propyl, n-butyl methanesulphonate have been determined over sufficient range of temperature to permit an evaluation of the corresponding enthalpy, entropy, and heat capacity terms for the activation process. Changes in these derived parameters are related to characteristic differences in solvation and mechanism as a consequence of changes in the structure of the hydrolyzing ester.

Heat capacity of activation for the hydrolysis of methanesulfonyl chloride and benzenesulfonyl chloride in light and heavy water

1969 ◽  
Vol 47 (22) ◽  
pp. 4199-4206 ◽  
Author(s):  
R. E. Robertson ◽  
B. Rossall ◽  
S. E. Sugamori ◽  
L. Treindl
Keyword(s):  
Heat Capacity ◽  
Free Energy ◽  
Temperature Dependence ◽  
Heavy Water ◽  
Bond Formation ◽  
Sulfonyl Chlorides ◽  
Benzenesulfonyl Chloride ◽  
Methanesulfonyl Chloride ◽  
Hydrolysis Of ◽  
Parameter Temperature Dependence

Rates of solvolysis of methanesulfonyl chloride and benzenesulfonyl chloride have been determined in H2O and D2O. The free energy, enthalpy, entropy, and heat capacity of activation were calculated. The exceptional accuracy of the data permitted an estimation of dΔCp≠/dT from a four parameter temperature dependence of the kinetic rates.From these data we conclude that both sulfonyl chlorides hydrolyse by the same mechanism (Sn2) The change in R from CH3 to C6H5 in RSO2Cl did not alter ΔCp≠ but ΔS≠ (20°) was changed from −8.32 to −13.25 cal deg−1 mole−1, respectively. The significance of this difference is attributed to the probability of bond formation rather than to differences in solvent reorganization.

scholarly journals Propranolol Inhibits Hyphal Development in Candida albicans

2002 ◽  
Vol 46 (11) ◽  
pp. 3617-3620 ◽  
Author(s):  
Carol A. Baker ◽  
Kevin Desrosiers ◽  
Joseph W. Dolan
Keyword(s):  
Growth Rate ◽  
Candida Albicans ◽  
Phosphatidic Acid ◽  
Rate Data ◽  
Dimorphic Transition ◽  
Hyphal Development ◽  
Germ Tubes ◽  
Hydrolysis Of

ABSTRACT Propranolol was used to investigate the role of phosphatidic acid (PA) and diacylglycerol in the dimorphic transition in Candida albicans. Propranolol was able to inhibit the appearance of germ tubes without decreasing growth rate. Data suggest that inhibition of morphogenesis may be due to binding by propranolol of PA derived from PLD1 hydrolysis of phosphatidylcholine.

Bioenergetics of Na+ transport across frog skin: chemical and electrical measurements

1983 ◽  
Vol 245 (6) ◽  
pp. F691-F700 ◽  
Author(s):  
M. M. Civan ◽  
K. Peterson-Yantorno ◽  
D. R. DiBona ◽  
D. F. Wilson ◽  
M. Erecinska
Keyword(s):  
Free Energy ◽  
Frog Skin ◽  
Atp Hydrolysis ◽  
Transepithelial Transport ◽  
Base Line ◽  
Free Energies ◽  
Electrical Measurements ◽  
Far From Equilibrium ◽  
The Difference ◽  
Hydrolysis Of

Enzymatically prepared split frog skins consisted purely of epithelial cells. Electrical parameters and the cell contents of ATP, ADP, phosphocreatine (PCr), creatine, inorganic phosphate, protein, and water were measured in skins maintained at room temperature. Studies were conducted under base-line conditions, 15 and 60 min after adding vasopressin, and 30 min after adding amiloride. Intracellular ionic activities and concentrations were obtained from previous results. The data demonstrated that 1) the base-line concentration ratio of PCr/ATP was 0.53 +/- 0.03; 2) the average molar free energy of hydrolysis of intracellular ATP was approximately 15.0 kcal X mol-1 under control conditions, changing by less than or equal to 3% with changes in transport; and 3) the free energy of extruding 3 mol of Na+ and accumulating 2 mol of K+ was approximately 9.8 kcal X mol-1 under base-line conditions; the difference between the molar free energies of ATP hydrolysis and of transport work remained large, despite large changes in transepithelial transport. The simplest conclusion is that the Na+ pump of frog skin operates far from equilibrium.

SOME ASPECTS OF THE ENZYMIC HYDROLYSIS OF URINARY 17-KETOSTEROID CONJUGATES

1960 ◽  
Vol 38 (1) ◽  
pp. 769-776
Author(s):  
R. Hobkirk ◽  
J. J. Cohen
Keyword(s):  
Liver Enzymes ◽  
Striking Difference ◽  
Degree Of Hydrolysis ◽  
Enzyme Preparations ◽  
Bacterial Preparation ◽  
Bacterial Enzyme ◽  
The Difference ◽  
Normal Urine ◽  
High Degree ◽  
Hydrolysis Of

Four enzyme preparations containing β-glucuronidase, of bacterial, mammalian, and molluscan origin, have been shown to be equally effective in liberating 17-ketosteroids (17-KS) of the 5β-(etiocholane) configuration in normal urine. The bacterial preparation releases steroids of the 5α-(androstane) configuration more rapidly than do the molluscan enzymes and with much greater ease than does the liver enzyme. In view of the data obtained it seems unlikely that the striking difference between the bacterial and liver enzymes can be due to the hydrolysis of some labile conjugate, such as sulphate, by the former and not by the latter. Possibilities that the difference is due to the hydrolysis of an unknown type of urinary conjugate by the bacterial preparation, or to the low specificity of the bacterial β-glucuronidase, are discussed. The high degree of hydrolysis of 17-KS conjugates by the bacterial enzyme followed by solvolysis suggests this as a most useful hydrolytic procedure.

The log kexovs. log kendo correlation as a mechanistic criterion; on the mechanisms of solvolysis of norbornyl derivatives and base-catalyzed isotope exchange of norbornanones

1976 ◽  
Vol 54 (5) ◽  
pp. 678-684 ◽  
Author(s):  
Sujit Banerjee ◽  
Nick Henry Werstiuk
Keyword(s):  
Transition State ◽  
Exchange Rates ◽  
Isotope Exchange ◽  
Transition States ◽  
Substituent Effects ◽  
Proton Exchange ◽  
Hydrogen Deuterium Exchange ◽  
Rate Data ◽  
Hydrogen Deuterium ◽  
The Difference

Rate data for the acetolysis of exo-norbornyl-sulfonates have been correlated with those for the corresponding endo isomers. It is shown that the slopes of the log kexovs. log kendo plots reflect the difference in delocalization between the transition states derived from the exo and endo isomers, respectively. The log kexovs. log kendo plot, which is comprised of the parent norbornyl sufonate and its derivatives substituted at the 5, 6, and 7 positions, has a slope of 1.11 ± 0.08, which establishes that σ bridging is absent in the transition state obtained from the exo isomer. A similar analysis of base-catalyzed hydrogen–deuterium exchange rates of norbornanones reveals that exo proton exchange is more sensitive to substituent effects than the corresponding endo process.

Sign in / Sign up

Export Citation Format

Share Document