A bimolecular mechanism for substitution

1968 ◽  
Vol 90 (21) ◽  
pp. 5928-5929 ◽  
Author(s):  
John N. Armor ◽  
Hans A. Scheidegger ◽  
Henry. Taube
Keyword(s):  
Bimolecular Mechanism

The photochemical and thermal decompositions of hydrogen sulphide

1953 ◽  
Vol 216 (1126) ◽  
pp. 344-361 ◽  
Keyword(s):  
Thermal Decomposition ◽  
Quantum Yield ◽  
Hydrogen Sulphide ◽  
Low Temperatures ◽  
Room Temperature ◽  
Large Fraction ◽  
Kcal Mole ◽  
Hydrogen Atoms ◽  
Photochemical Decomposition ◽  
Bimolecular Mechanism

The photochemical decomposition of hydrogen sulphide has been investigated at pressures between 8 and 550 mm of mercury and at temperatures between 27 and 650° C, using the narrow cadmium line ( λ 2288) and the broad mercury band (about λ 2550). At room temperature the quantum yield increases with pressure from 1.09 at 30 mm to 1.26 at 200 mm. Above 200 mm pressure there was no further increase in the quantum yield. Temperature had little effect on the quantum yield at λ 2550, but there was a marked increase in the rate of hydrogen production between 500 and 650° C with 2288 Å radiation. This may have been caused by the decomposition of excited hydrosulphide radicals. The results are consistent with a mechanism involving hydrogen atoms and hydrosulphide radicals. The mercury-photosensitized reaction is less efficient than the photochemical decomposition, the quantum yield being only about 0.45. The efficiency increased with temperature and approached unity at high temperatures and pressures. This agrees with the suggestion that a large fraction of the quenching collisions lead to the formation of Hg ( 3 P 0 ) atoms. The thermal decomposition is heterogeneous at low temperatures and becomes homogeneous and of the second order at 650° C. The experimental evidence suggests the bimolecular mechanism 2H 2 S → 2H 2 + S 2 . The activation energies are 25 kcal/mole (heterogeneous) and 50 kcal/mole (homogeneous).

Kinetics of the hydrolysis of acyl chlorides in pure water

1967 ◽  
Vol 45 (14) ◽  
pp. 1619-1629 ◽  
Author(s):  
A. Queen
Keyword(s):  
Pure Water ◽  
Activation Parameters ◽  
Acyl Chlorides ◽  
Reversible Addition ◽  
Electron Donation ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Chlorine Bond ◽  
Oxygen Bond ◽  
Bimolecular Mechanism

The activation parameters ΔH≠, ΔS≠, and ΔCP≠ for the hydrolyses of a series of alkyl chloroformates and dimethylcarbamyl chloride in water have been determined. The results indicate that, with increasing electron donation to the chlorocarbonyl group, the mechanism changes from bimolecular to unimolecular (SN1) displacement at this position. For isopropyl chloroformate, some concurrent alkyl–oxygen bond fission is also indicated. The bimolecular mechanism involves reversible addition of water to the carbonyl group followed by ionization of the carbon–chlorine bond.

Bistability and the ordered bimolecular mechanism

1991 ◽  
Vol 69 (9) ◽  
pp. 661-664 ◽  
Author(s):  
K. W. Raymond ◽  
Y. Pocker
Keyword(s):  
Steady State ◽  
Kinetic Constant ◽  
Substrate Inhibition ◽  
Enzymatic Reaction ◽  
Reaction System ◽  
Computational Approach ◽  
Instantaneous Velocity ◽  
Liver Alcohol Dehydrogenase ◽  
Horse Liver ◽  
Bimolecular Mechanism

An equation describing the instantaneous velocity of an ordered bimolecular enzymatic reaction that exhibits inhibition by substrate and product was derived. Using kinetic constant values for horse liver alcohol dehydrogenase, the velocity expression was applied to an open-reaction system. The calculated steady-state surfaces displayed regions of bistability, which further substantiates the link between substrate inhibition and multiple steady states. This general computational approach may be applied to any system that can be described by an instantaneous velocity equation.Key words: bistability, steady state, enzyme kinetics.

scholarly journals Efficient Bimolecular Mechanism of Photochemical Hydrogen Production Using Halogenated Boron-Dipyrromethene (Bodipy) Dyes and a Bis(dimethylglyoxime) Cobalt(III) Complex

2016 ◽  
Vol 120 (3) ◽  
pp. 527-534 ◽  
Author(s):  
Randy P. Sabatini ◽  
Brian Lindley ◽  
Theresa M. McCormick ◽  
Theodore Lazarides ◽  
William W. Brennessel ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Boron Dipyrromethene ◽  
Bimolecular Mechanism

Dihydride transfer: a bimolecular mechanism in the isomerization of cis-dihydridobromo(carbonyl)[bis(diphenylphosphino)ethane]iridium, IrH2Br(CO)(dppe)

1987 ◽  
Vol 109 (10) ◽  
pp. 2963-2968 ◽  
Author(s):  
Amanda J. Kunin ◽  
Curtis E. Johnson ◽  
John A. Maguire ◽  
William D. Jones ◽  
Richard Eisenberg
Keyword(s):  
Bimolecular Mechanism

scholarly journals The rates of transformation in ethyl alcohol of ammonium and ethylammonium cyanates to the corresponding ureas

1938 ◽  
Vol 168 (933) ◽  
pp. 206-218 ◽  
Keyword(s):  
Ionic Strength ◽  
Ethyl Alcohol ◽  
Reaction Kinetic ◽  
Average Concentration ◽  
Forward Reaction ◽  
Velocity Constant ◽  
Low Concentrations ◽  
Hückel Theory ◽  
Complete Dissociation ◽  
Bimolecular Mechanism

In aqueous and aqueous ethyl alcoholic solutions ammonium and alkylammonium cyanates seem to be converted to the corresponding ureas by a reversible bimolecular mechanism associated primarily until univalent annnoniurn (or alkylammonium) and cyanate ions. Thus, if C a and C b are the concentrations of the ionioc reactants A and B , based on the conception of complete dissociation, and the reverse reaction is negligible, the velocity v of the forward reaction is represented by the equation, v = k 0 C a C b F , where k 0 is the velocity constant, and F is a reaction kinetic factor which is at least qualitatively represented by f a f b /f x , as defined by Brénsted (1922). f a f b f x represent, respectively, the activity coefficients of the reactants and a critical complex X , which, in our case, is a neutral molecule of which the activity coefficient may be taken to be unity. For example, when the logarithm of k c , the so-called velocity constant determined experimentally at various concentrations from the equation v = k c C a C b ( k c k 0 F ), is plotted against the squarer root of the average ionic strength (here, simply the average concentration) of the interval to which it refers, a curve is obtained which at low concentrations approximates to the linear relationship required by the Debye-Hückel theory. Miller (1934, 1935) showed this for methylammonium cyanate in water and in 98.1% aqueous ethyl alcohol. Warner and Stitt (1933) obtained a similar result for ammonium cyanate in water. The rates of transformation of ammonium and methylammonium cyanates in water were influenced by neutral salts in the manner predicted by Brönsted.

Comments on “Skeletal Isomerization of Butene:  On the Role of the Bimolecular Mechanism”

1998 ◽  
Vol 37 (1) ◽  
pp. 300-302 ◽  
Author(s):  
M. Guisnet ◽  
P. Andy ◽  
N. S. Gnep ◽  
C. Travers ◽  
E. Benazzi
Keyword(s):  
Skeletal Isomerization ◽  
Bimolecular Mechanism
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