Deuterium Isotope Effects on Reaction Rates of Ground State Zr with Ethylene and Propylene

2000 ◽  
Vol 104 (7) ◽  
pp. 1524-1531 ◽  
Author(s):  
Meredith Porembski ◽  
James C. Weisshaar
Keyword(s):  
Ground State ◽  
Isotope Effects ◽  
Reaction Rates ◽  
Deuterium Isotope Effects

Hydrocarbon C-H bond activation by rhodium porphyrins

2004 ◽  
Vol 08 (02) ◽  
pp. 103-110 ◽  
Author(s):  
Weihong Cui ◽  
Bradford B. Wayland
Keyword(s):  
Transition State ◽  
High Selectivity ◽  
Bond Activation ◽  
Isotope Effects ◽  
Reaction Rates ◽  
Methane Activation ◽  
Porphyrin Ligand ◽  
Deuterium Isotope Effects ◽  
Rhodium Porphyrins ◽  
Steric Constraints

Rhodium porphyrins provide a variety of C-H bond reactions with both aromatic and aliphatic hydrocarbons that acquire unusual selectivity in part through the steric requirements of the porphyrin ligand. Rhodium(III) porphyrins selectively react with aromatic C-H bonds by electrophilic substitution with the virtual exclusion of aliphatic C-H bond activation. Rhodium(II) porphyrins react by a metal-centered radical pathway with alkyl aromatics and alkanes selectively at the alkyl C-H bond with total exclusion of aromatic C-H bond activation. Reactions of rhodium(II) metalloradicals with alkyl C-H bonds have large deuterium isotope effects, small activation enthalpies and large negative activation entropies consistent with a near linear symmetrical four-centered transition state ( Rh ˙⋯ H ⋯ C ⋯˙Rh). The nature of this transition state and the dimensions of rhodium porphyrins provide steric constraints that preclude aromatic C-H bond reactions and give high kinetic preference for methane activation as the smallest alkane substrate. Rhodium(II) tethered diporphyrin bimetalloradical complexes convert the C-H bond reactions to bimolecular processes with dramatically increased reaction rates and high selectivity for methane activation.

Pure rotational spectrum of 13CD4 and isotope effects on the tensorial centrifugal-distortion constants of methane

1987 ◽  
Vol 65 (1) ◽  
pp. 32-37 ◽  
Author(s):  
W. A. Kreiner ◽  
P. Müller ◽  
L. Jörissen ◽  
M. Oldani ◽  
A. Bauder
Keyword(s):  
Fourier Transform ◽  
Radio Frequency ◽  
Ground State ◽  
Isotope Effects ◽  
Double Resonance ◽  
Rotational Spectrum ◽  
Centrifugal Distortion ◽  
Theoretical Predictions ◽  
Deuterium Isotope Effects ◽  
Centrifugal Distortion Constants

Infrared-laser – radio-frequency double-resonance experiments and pulsed-microwave Fourier-transform measurements have been performed with 13CD4. From 25 observed ΔJ = 0 transitions in the vibronic ground state, the tensorial centrifugal-distortion constants Dt = 32.6600(12) kHz, H4t = −2.0302(61) Hz, H6t = 1.1692(29) Hz, L4t = 1.201(77) × 10−4 Hz, L6t = −1.353(63) × 10−4 Hz, and L8t = −1.466(46) × 10−4 Hz have been determined. Experimental carbon-13 and deuterium isotope effects on the tensorial centrifugal-distortion constants of methane have been compared with theoretical predictions.

Reactions of alicyclic ketones in carbon tetrachloride. I, The kinetics of the chlorination of cyclopentanone and cyclohexanone catalyzed by hydrogen chloride

1986 ◽  
Vol 64 (9) ◽  
pp. 1681-1689 ◽  
Author(s):  
Eize J. Stamhuis ◽  
Henk Maatman ◽  
Henk Stinissen ◽  
Geert E. H. Joosten
Keyword(s):  
Carbon Tetrachloride ◽  
Hydrogen Chloride ◽  
Isotope Effects ◽  
Reaction Rates ◽  
Zero Order ◽  
Rate Determining Step ◽  
Conjugate Acid ◽  
Deuterium Isotope Effects ◽  
Self Association ◽  
Kinetics Of

The kinetics of the direct chlorination of cyclopentanone (cp) and cyclohexanone (ch) in carbon tetrachloride, catalyzed by hydrogen chloride, was studied. The rate of chlorination, measured by flow and stopped-flow techniques, is zero order in chlorine; the order in cp and ch increases from 1 at [cp] and [ch] of 0.01 M concentration to 2 at concentrations of 1 M. This is explained by self-association of the ketones in carbon tetrachloride solutions. The order in hydrogen chloride is 1. Since this compound is one of the products, the reaction is autocatalytic. Deuterium isotope effects and the kinetic data strongly point to a mechanism in which the oxygen-protonated monomeric ketone is α-carbon deprotonated in a rate-determining step. This step, which is catalyzed by the bases cp or ch, respectively, leads to the corresponding enol as intermediate. The enol is then chlorinated very rapidly. In addition to the chloro ketone, very reactive chloride anions are formed. A small fraction of these anions deprotonate α- or α′-carbon atoms of the oxygen-conjugate acid of the monochloro ketone. The remainder are captured by HCl to form energetically more favored Cl--(HCl)n complexes with n = 1, 2, or 3. This explains why, even at low conversions of the ketones, substantial amounts of the various dichloro isomers are formed in addition to monochloro products. A rate expression is derived, which excellently describes the experimentally obtained rates of chlorination of cp and ch over a range of reaction rates of more than three decades.

Mechanism of hydration and isomerisation of 4-ethylidene-2,6-di-tert-butyl-2,5-cyclohexadien-1-one. Kinetics, acid-base catalysis and solvent deuterium isotope effects

1979 ◽  
Vol 44 (1) ◽  
pp. 110-122 ◽  
Author(s):  
Jiří Velek ◽  
Bohumír Koutek ◽  
Milan Souček
Keyword(s):  
Aqueous Medium ◽  
Rate Equation ◽  
Kinetic Data ◽  
Isotope Effects ◽  
Base Catalysis ◽  
Quinone Methide ◽  
Reaction Products ◽  
Acid Base ◽  
Deuterium Isotope Effects ◽  
Hydroxybenzyl Alcohol

Competitive hydration and isomerisation of the quinone methide I at 25 °C in an aqueous medium in the region of pH 2.4-13.0 was studied spectrophotometrically. The only reaction products in the studied range of pH are 4-hydroxybenzyl alcohol (II) and 4-hydroxystyrene (III). The form of the overall rate equation corresponds to a general acid-base catalysis. The mechanism of both reactions for three markedly separated pH regions is discussed on the basis of kinetic data and solvent deuterium effect.

The Reaction and Microscopic Electron Properties from Dynamic Evolutions of Condensed-Phase RDX Under Shock Loading

2020 ◽  
Vol 75 (4) ◽  
pp. 285-291
Author(s):  
Jiao-Nan Yuan ◽  
Hai-Chao Ren ◽  
Yong-Kai Wei ◽  
Wei-Sen Xu ◽  
Guang-Fu Ji ◽  
...  
Keyword(s):  
Shock Wave ◽  
Ground State ◽  
Shock Loading ◽  
Reaction Rates ◽  
Reaction Products ◽  
Decomposition Rates ◽  
Multi Scale ◽  
Wave Velocities ◽  
Wide Gap ◽  
Reaction Initiation

AbstractMicroscopic electron properties of α-hexahydro-1,3,5-trinitro-1,3,5-triazine (α-RDX) with different shock wave velocities have been investigated based on molecular dynamics together with multi-scale shock technique. The studied shock wave velocities are 8, 9 and 10 km ⋅ s−1. It has been said that the shock sensitivity and reaction initiation of explosives are closely relevant with their microscopic electron properties. The reactions, including the reaction products, which are counted from the trajectory during the simulations are analysed first. The results showed that the number of the products strictly rely on shock wave velocities. The reaction rates and decomposition rates are also studied, which showed the differences between the different shock velocities. The results of electron properties show that α-RDX is a wide-gap insulator in the ground state and the metallisation conditions of shocked RDX are determined, which are lower than under-static high pressure.

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