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.

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.

HYDROLYSIS OF A SERIES OF PRIMARY ALKYL CHLOROSULFATES: ENTROPY OF ACTIVATION AS A CRITERION OF FRAGMENTATION IN SOLVOLYTIC REACTIONS

1965 ◽  
Vol 43 (3) ◽  
pp. 556-564 ◽  
Author(s):  
E. Buncel ◽  
J. P. Millington
Keyword(s):  
Transition State ◽  
Multiple Bond ◽  
Aqueous Dioxane ◽  
Methyl Ethyl ◽  
Straight Chain ◽  
Leaving Group ◽  
Entropy Of Activation ◽  
Hydrolysis Of ◽  
Chlorine Bond

The solvolysis of the series of alkyl chlorosulfates, ROSO2Cl, where R = methyl, ethyl, n-propyl, isobutyl, and neopentyl, has been studied in 10 M aqueous dioxane. The relative reactivities fit well a solvolytic mechanism involving displacement by water on carbon, with OSO2Cl as the leaving group. The change in mechanism of solvolysis from bimolecular with the straight-chain chlorosulfates to unimolecular with neopentyl chlorosulfate is shown by the absence of the lyate ion effect and the observation of rearrangement in the latter case.The entropies of activation in chlorosulfate solvolysis appear to be abnormally large. It is proposed that the abnormal ΔS≠ indicates a transition state in which both carbon–oxygen and sulfur–chlorine bond weakening occurs. It is shown that some other solvolytic reactions that are characterized by abnormally high entropies of activation may be interpreted on the basis of multiple bond fission (fragmentation). The mechanism of SNi reactions is considered in this context.

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.

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.

scholarly journals The homogeneous unimolecular decomposition of gaseous alkyl nitrites - IV—The decomposition of Iso -propyl nitrite

1935 ◽  
Vol 151 (874) ◽  
pp. 685-693 ◽  
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Pressure Change ◽  
Methyl Ethyl ◽  
Unimolecular Decomposition ◽  
Decomposition Rates ◽  
Straight Chain ◽  
Alkyl Nitrites ◽  
Branched Chain ◽  
Reaction Vessels

It has already been shown that the first three straight chain members of the nitrite homologous series, i. e ., methyl, ethyl, and n -propyl nitrites, have exhibited in their thermal decomposition the characteristics pertaining to homogeneous unimolecular reactions. This paper deals with the investigation carried out on iso -propyl nitrite decomposition. This member of the series is particularly interesting as it allows comparison to be made between a straight-chain and a branched-chain isomer. The effect of these chemical configurations on the activation energy and the decomposition rates can be very effectively studies as no complications enter into the reactions to confuse measurements. Experimental Reaction velocities were measured as before by observing the rate of pressure change in a system at constant volume. The reaction vessels were Pyrex glass bulbs with a capacity of about 125 cc. The apparatus was similar to that used in previous experiments. The connecting tubing was heated to 105° C to prevent any of the products of the reaction condensing out. Control and measurement of the temperature was carried out as before. The temperature could be maintained constant to within 0·25° C.

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.

Heat Capacity of Activation for the Hydrolysis of 2,2-Dihalopropanes1

1966 ◽  
Vol 88 (7) ◽  
pp. 1363-1365 ◽  
Author(s):  
A. Queen ◽  
R. E. Robertson
Keyword(s):  
Heat Capacity ◽  
Hydrolysis Of

The Hydrolysis of Disubstituted Alkyl Phosphorochloridates and N,N,N′,N′-Tetra-stibstituted Phosphorodiamidic Chlorides in Water and Deuterium Oxide: Heat Capacity of Activation and Kinetic Solvent Isotope Effects

1973 ◽  
Vol 51 (4) ◽  
pp. 597-603 ◽  
Author(s):  
E. C. F. Ko ◽  
R. E. Robertson
Keyword(s):  
Heat Capacity ◽  
Thermodynamic Parameters ◽  
Alkyl Group ◽  
Deuterium Oxide ◽  
Isotope Effects ◽  
Potential Relationship ◽  
Mechanism Of Reaction ◽  
Solvent Isotope ◽  
Hydrolysis Of ◽  
Solvent Isotope Effects

The pseudo-thermodynamic parameters, ΔH≠, ΔS≠, and ΔCp≠ and the kinetic solvent isotope effects have been determined for the three alkyl-phosphorochloridates, where the alkyl group is ethylisopropyl and n-propyl; for tetra-methyl and tetra-ethyl phosphorodiamidic chlorides; the di-n-propyl and di-isopropyl analog, the di(isopropylmethylcarbinyl)phosphorochloridate and the tetra-ethylthiophosphorodiamidic chloride. These compounds have a potential relationship to compounds used as insecticides and as polymers. The mechanism of reaction is discussed on the basis of these data.

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