Kinetic and Equilibrium Studies of the Reactions of 2,4,6-Trinitrotoluene and 2,4,6-Trinitrotoluene-d3 with Sodium and Potassium t-Butoxide in t-Butanol

1974 ◽  
Vol 52 (12) ◽  
pp. 2306-2315 ◽  
Author(s):  
Erwin Buncel ◽  
Albert Richard Norris ◽  
Kenneth Edwin Russell ◽  
Harold Wilson
Keyword(s):  
Initial Rate ◽  
Forward Rate ◽  
Specific Rate ◽  
Equilibrium Studies ◽  
Proton Abstraction ◽  
Kinetic Isotope ◽  
Forward Rate Constant ◽  
Hydrogen Deuterium ◽  
Reaction In Solution ◽  
Sodium And Potassium

The reactions of 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitrotoluene fully deuterated at the methyl position (TNT-d3) with sodium and potassium t-butoxide in t-butanol have been studied. With TNT as the substrate, proton abstraction by ion-paired sodium or potassium t-butoxide appears to be the predominant reaction in solution. With sodium t-butoxide as base, the forward rate constant for proton abstraction at 30.0 °C (Kf,ip) is 6000 ± 400 M−1 s−1 while ΔH≠ and ΔS≠ for the reaction are 4.2 ± 0.3 kcal mol−1 and −27 ± 2 cal deg−1 mol−1, respectively. With TNT-d3 as the substrate, formation of a TNT-d3-t-butoxide ion σ-complex occurs simultaneously with deuteron abstraction. Specific rate constants for the two processes have been determined at 30.0 °C. Initial rate studies establish a hydrogen-deuterium kinetic isotope effect of 8 ± 1 for the formation of the anion in t-butanol.

scholarly journals l-mandelate dehydrogenase from Rhodotorula graminis: comparisons with the l-lactate dehydrogenase (flavocytochrome b2) from Saccharomyces cerevisiae

1993 ◽  
Vol 290 (1) ◽  
pp. 103-107 ◽  
Author(s):  
O Smékal ◽  
M Yasin ◽  
C A Fewson ◽  
G A Reid ◽  
S K Chapman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Lactate Dehydrogenase ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Dimensional Structure ◽  
Striking Difference ◽  
Kinetic Properties ◽  
Proton Abstraction ◽  
Rate Determining Step ◽  
Kinetic Isotope

L-Lactate dehydrogenase (L-LDH) from Saccharomyces cerevisiae and L-mandelate dehydrogenase (L-MDH) from Rhodotorula graminis are both flavocytochromes b2. The kinetic properties of these enzymes have been compared using steady-state kinetic methods. The most striking difference between the two enzymes is found by comparing their substrate specificities. L-LDH and L-MDH have mutually exclusive primary substrates, i.e. the substrate for one enzyme is a potent competitive inhibitor for the other. Molecular-modelling studies on the known three-dimensional structure of S. cerevisiae L-LDH suggest that this enzyme is unable to catalyse the oxidation of L-mandelate because productive binding is impeded by steric interference, particularly between the side chain of Leu-230 and the phenyl ring of mandelate. Another major difference between L-LDH and L-MDH lies in the rate-determining step. For S. cerevisiae L-LDH, the major rate-determining step is proton abstraction at C-2 of lactate, as previously shown by the 2H kinetic-isotope effect. However, in R. graminis L-MDH the kinetic-isotope effect seen with DL-[2-2H]mandelate is only 1.1 +/- 0.1, clearly showing that proton abstraction at C-2 of mandelate is not rate-limiting. The fact that the rate-determining step is different indicates that the transition states in each of these enzymes must also be different.

Hydrogen‐Deuterium Kinetic Isotope Effect at Very High Temperature

1962 ◽  
Vol 36 (2) ◽  
pp. 463-468 ◽  
Author(s):  
Harold S. Johnston ◽  
Eugene Tschuikow‐Roux
Keyword(s):  
High Temperature ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Kinetic Isotope ◽  
Hydrogen Deuterium ◽  
Very High

Chemical Properties of Zwitterionic Imidazolium Alkanecarboxylates Studied in Gas-Phase by Electrospray Ionization – Collision-Induced Dissociation / Cviterjonu Tipa Imidazolija Alkānkarboksilātu Ķīmiskās Īpašības Gāzes Fāzē, Kas Pētītas Ar Elektroizsmidzināšanas Jonizāciju – Sadursmju Inducēto Disociāciju

2012 ◽  
Vol 51 (3) ◽  
pp. 249-256
Author(s):  
A. Podjava ◽  
P. Mekss ◽  
A. Zicmanis ◽  
S. Krasnov
Keyword(s):  
Gas Phase ◽  
Chemical Properties ◽  
Collision Induced Dissociation ◽  
Potassium Ions ◽  
Hydrogen Deuterium Exchange ◽  
Carboxylate Group ◽  
Hydrogen Deuterium ◽  
Ionization Mode ◽  
Sodium And Potassium ◽  
Phase Chemical

Gas-phase chemical properties of several (1-methylimidazol-3-io)-alkane-1-carboxylates (alkane=ethane, propane and butane) have been investigated in this study. These substances are synthesized using classical transformations and analyzed in positive ionization mode using collision-induced dissociation (0-50 eV). These experiments were carried out in both deuterated and undeuterated solvent media. The data obtained in this study show, that carboxylate group weakly influences fragmentation of zwitterionic imidazolium carboxylates in positive electrospray mode. On the other hand, these compounds exert a tendency to form various adducts with sodium and potassium ions and to participate in hydrogen/deuterium exchange in the gas phase.

Using Incoming Nucleophile Primary Hydrogen−Deuterium Kinetic Isotope Effects To Model the SN2 Transition State

2000 ◽  
Vol 122 (30) ◽  
pp. 7342-7350 ◽  
Author(s):  
Terry Koerner ◽  
Yao-ren Fang ◽  
Kenneth Charles Westaway
Keyword(s):  
Transition State ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope ◽  
Hydrogen Deuterium

scholarly journals P3331Obesity is associated with an increase in the forward rate constant of the creatine kinase reaction

2017 ◽  
Vol 38 (suppl_1) ◽  
Author(s):  
J. Rayner ◽  
W. Clarke ◽  
M.A. Peterzan ◽  
C.T. Rodgers ◽  
S. Neubauer ◽  
...  
Keyword(s):  
Creatine Kinase ◽  
Rate Constant ◽  
Forward Rate ◽  
Kinase Reaction ◽  
Forward Rate Constant ◽  
Creatine Kinase Reaction

Isotope effects in nucleophilic substitution reactions. V. The mechanism of the decomposition of 1-phenylethyldimethylphenylammonium halides in chloroform

1986 ◽  
Vol 64 (6) ◽  
pp. 1206-1214 ◽  
Author(s):  
Helen Alma Joly ◽  
Kenneth Charles Westaway
Keyword(s):  
Ground State ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Steric Effects ◽  
Halide Ions ◽  
Substitution Reactions ◽  
Kinetic Isotope ◽  
Hydrogen Deuterium ◽  
Primary Substrate ◽  
Triple Ion

Secondary α and β hydrogen–deuterium kinetic isotope effects have been used together to show that the SN reaction between 1-phenylethyldimethylphenylammonium ion and bromide or iodide ion in chloroform occurs by way of an SN2 mechanism within a triple ion in spite of the fact that it reacts faster than the primary substrate, benzyldimethylphenylammonium bromide. The very loose transition state and steric effects in the ground state appear to be responsible for the unusually fast SN2 reactions between 1-phenylethyldimethylphenylammonium ion and halide ions in chloroform.

Primary kinetic isotope effect in the gas phase photochlorination of ethyl chloride-1-d1

1984 ◽  
Vol 62 (5) ◽  
pp. 899-906 ◽  
Author(s):  
Jan Niedzielski ◽  
T. Yano ◽  
E. Tschuikow-Roux
Keyword(s):  
Activation Energy ◽  
Gas Phase ◽  
Isotope Effect ◽  
Ground State ◽  
Rate Constants ◽  
Kinetic Isotope Effect ◽  
Kinetic Isotope ◽  
Primary Reference ◽  
Hydrogen Deuterium ◽  
Increasing Temperature

The abstraction of hydrogen/deuterium from CH3CHDCl by ground state chlorine atoms produced photolytically from Cl2 has been investigated at temperatures betwen 280 and 368 K. The relative rates for the internal competition[Formula: see text]are found to conform to an Arrhenius rate law:[Formula: see text]These data, taken together with the external competition results for the C2H5Cl/CH3CHDCl system, in conjunction with the competitive results using CH4 as a primary reference, have yielded the rate constants (cm3 s−1):[Formula: see text]The relatively weak primary kinetic isotope effect, kH/kD, decreases with increasing temperature from 1,855 at 280 K to 1.66 at 365 K. The results are compared with those obtained based on the BEBO method. While both the trend and the magnitude of the kinetic isotope effect are satisfactorily predicted, the activation energy is not.

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