A homoallyl radical rearrangement. Kinetics of the isomerization of the 2,2-dimethyl-3-buten-1-yl radical to the 1,1-dimethyl-3-buten-1-yl radical

1983 ◽  
Vol 61 (6) ◽  
pp. 1077-1081 ◽  
Author(s):  
Chryssostomos Chatgilialoglu ◽  
Keith U. Ingold ◽  
Irene Tse-Sheepy ◽  
John Warkentin
Keyword(s):  
Temperature Dependence ◽  
Epr Spectroscopy ◽  
Rate Constants ◽  
Alkyl Radical ◽  
Spin Trapping ◽  
Ring Closure ◽  
Rate Enhancement ◽  
Radical Rearrangement ◽  
Kinetics Of

Rate constants for the overall rearrangement of the 2,2-dimethyl-3-buten-1-yl radical to the 1,1 -dimethyl-3-buten-1-yl radical, kC=C, have been measured from −145 °C to −101 °C by kinetic epr spectroscopy and at 40 °C by spin trapping with 1-methyl-4-nitroso-3,5-diphenylpyrazole. The temperature dependence can be represented by[Formula: see text]where θ = 2.3RT kcal mol−1. This rearrangement, which must proceed via a 2,2-dimethylcyclopropylcarbinyl radical as an intermediate, is one of the fastest rearrangements involving a primary alkyl radical. At 25 °C, kC=C = 4.3 × 107 s−1, which makes this rearrangement about 10 000 times faster than the rearrangement of the simplest homoallyl radical, 3-buten-1-yl. This rate enhancement is attributed to steric acceleration of ring closure by the gem dimethyl groups (Thorpe–Ingold effect).

A homopropargyl radical rearrangement. Kinetics of the rearrangement of the 2,2,5,5,-tetramethyl-3-hexyn-1-yl radical

1980 ◽  
Vol 58 (4) ◽  
pp. 348-352 ◽  
Author(s):  
Keith U. Ingold ◽  
John Warkentin
Keyword(s):  
Temperature Dependence ◽  
Epr Spectroscopy ◽  
Rate Constants ◽  
Radical Rearrangement ◽  
Vinyl Radical ◽  
Kinetics Of

The rate constants for rearrangement of the 2,2,5,5-tetramethyl-3-hexyn-1-yl radical to the 2,6,6-trimethyl-4-heptyn-2-yl radical have been measured from 45 to 88 °C by kinetic epr spectroscopy. The temperature dependence can be represented by[Formula: see text]where θ = 2.3RT kcal mol−1. This rearrangement, which must involve an intermediate vinyl radical of the methylenecyclopropane type, is much slower than analogous rearrangement of homoallyl radicals but comparable in rate to rearrangement of homobenzyl (neophyl) radicals.

Kinetik der Reaktion von 2.4-Dinitrofluorbenzol mit Imidazol-, SH- und Imidazol-SH-Verbindungen / Kinetics of the Reaction of 2,4-dinitro-1-fluorobenzene with Imidazole-, SH- and Imidazole-SH-compounds

1971 ◽  
Vol 26 (10) ◽  
pp. 1010-1016 ◽  
Author(s):  
Renate Voigt ◽  
Helmut Wenck ◽  
Friedhelm Schneider
Keyword(s):  
Temperature Dependence ◽  
Rate Constants ◽  
Reaction Rate ◽  
Ph Dependence ◽  
First Order ◽  
Molecular Transfer ◽  
Thiolate Anion ◽  
Nucleophilic Reactivity ◽  
Kinetics Of ◽  
Lindley Equation

First order rate constants of the reaction of a series of SH-, imidazole- and imidazole/SH-compounds with FDNB as well as their pH- and temperature dependence were determined. Some of the tested imidazole/SH-compounds exhibit a higher nucleophilic reactivity as is expected on the basis of their pKSH-values. This enhanced reactivity is caused by an activation of the SH-groups by a neighbouring imidazole residue. The pH-independent rate constants were calculated using the Lindley equation.The kinetics of DNP-transfer from DNP-imidazole to SH-compounds were investigated. The pH-dependence of the reaction displays a maximum curve. Donor in this reaction is the DNP-imidazolecation and acceptor the thiolate anion.The reaction rate of FDNB with imidazole derivatives is two to three orders of magnitude slower than with SH-compounds.No inter- or intra-molecular transfer of the DNP-residue from sulfure to imidazole takes place.

Annealing experiments on CO2-bearing jadeite glass: an insight into the true temperature dependence of CO2 speciation in silicate melts

2001 ◽  
Vol 65 (6) ◽  
pp. 701-707 ◽  
Author(s):  
Y. Morizet ◽  
S. C. Kohn ◽  
R. A. Brooker
Keyword(s):  
Temperature Dependence ◽  
Rate Constants ◽  
Negative Charge ◽  
Silicate Melts ◽  
True Temperature ◽  
Carbonate Group ◽  
Image Position ◽  
Kinetics Of ◽  
Annealing Experiments ◽  
Insight Into

AbstractThe thermodynamics and kinetics of CO2 speciation in silicate melts have been studied by measuring the concentration of CO2mol and carbonate in jadeite glass annealed at 575, 450 and 400°C. Assuming that the reaction is1where CO2mol..Obr represents a CO2 molecule weakly bonded to a bridging oxygen in the network and CO3 represents a bridging carbonate group with no net negative charge, ΔH for the reaction is –17 (+4/–8) kJ mol−1 and ΔS is –24 (+6/–9) J K−1 mol−1. The rate of equilibration of the species was measured at each temperature and the rate constants were deduced. The temperature dependence of the rate constants was used to determine the activation energy of the forward and reverse reactions which are 68 (+3/–31) kJ mol−1 and 86 (+1/–69) kJ mol−1 respectively. The data suggest that CO2mol may be much more abundant in silicate melts than previously assumed on the basis of studies of CO2-bearing glasses. Models of solubility, diffusion, and isotope fractionation should take this into account.

KINETICS OF THE AQUEOUS ALKALINE HOMOGENOUS HYDROLYSIS OF HIGH EXPLOSIVE 1, 3,5,7-TETRAAZA- 1, 3,5,7-TETRANITROCYCLOOCTANE (HMX)

1994 ◽  
Vol 30 (3) ◽  
pp. 53-61 ◽  
Author(s):  
Harro M. Heilmann ◽  
Michael K. Stenstrom ◽  
Rolf P. X. Hesselmann ◽  
Udo Wiesmann
Keyword(s):  
Temperature Dependence ◽  
Alkaline Hydrolysis ◽  
Rate Constants ◽  
Elevated Temperatures ◽  
Second Order ◽  
Order Rate ◽  
Subsequent Calculation ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Order Rate Equation

In order to get basic data for the design of a novel treatment scheme for high explosives we investigated the kinetics for the aqueous alkaline hydrolysis of 1,3,5,7-tetraaza-1,3,5,7-tetranitrocyclooctane (HMX) and the temperature dependence of the rate constants. We used an HPLC procedure for the analysis of HMX. All experimental data could be fit accurately to a pseudo first-order rate equation and subsequent calculation of second-order rate constants was also precise. Temperature dependence could be modeled with the Arrhenius equation. An increase of 10°C led to an average increase in the second-order rate constants by the 3.16 fold. The activation energy of the second-order reaction was determined to be 111.9 ±0.76 kJ·moJ‒1. We found the alkaline hydrolysis to be rapid (less than 2.5% of the initial HMX-concentration left after 100 minutes) at base concentrations of 23 mmol oH‒/L and elevated temperatures between 60 and 80°C.

Synthesis and spin trapping kinetics of new alkyl substituted cyclic nitrones

1982 ◽  
Vol 60 (12) ◽  
pp. 1514-1522 ◽  
Author(s):  
D. L. Haire ◽  
Edward G. Janzen
Keyword(s):  
Comparative Study ◽  
Rate Constants ◽  
Spin Trap ◽  
Spin Trapping ◽  
Absolute Rate ◽  
Cyclic Nitrones ◽  
The Absolute ◽  
Kinetics Of

Three new nitrones, 5-n-propyl-5-methyl-1-pyrroline-N-oxide (PMPO), 5-n-hexyl-5-methyl-1-pyrroline-N-oxide (HMPO), and 5-n-decyl-5-methyl-1-pyrroline-N-oxide (DeMPO), amphiphilic versions of the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), have been synthesized. A comparative study of the absolute rate constants for formation and decay of the tert-butoxyl spin adducts to these cyclic nitrones as well as 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (M4PO) has been undertaken using esr kinetic techniques.

Oxidation kinetics of trans-aqua-bis(ethylenediamine)-isothiocyanatocobalt(III) ion with peroxodisulphate

1979 ◽  
Vol 44 (4) ◽  
pp. 1052-1059 ◽  
Author(s):  
Olga Volárová ◽  
Vladislav Holba
Keyword(s):  
Ionic Strength ◽  
Temperature Dependence ◽  
Rate Constants ◽  
Oxidation Kinetics ◽  
Salt Effect ◽  
Activation Parameters ◽  
Thermodynamic Activation Parameters ◽  
Ionic Reactions ◽  
Kinetics Of

Oxidation kinetics of trans-aqua-bis(ethylenediamine)cobalt(III) ion with peroxodisulphate have been investigated in 0.01M-HClO4 medium within the ionic strength and temperature intervals 0.0411 to 0.4415M and 315.5 to 336.9 K, respectively. From the temperature dependence of the rate constants extrapolated to zero ionic strength the extrapolated values of thermodynamic activation parameters have been calculated. The data obtained by investigation of the primary salt effect have been confronted with relations valid for ionic reactions.

The Mechanism of Accelerator Action. Reaction of Mercaptobenzothiazole with Sulfur

1958 ◽  
Vol 31 (2) ◽  
pp. 343-347 ◽  
Author(s):  
B. Dogadkin ◽  
I. Tutorskiĭ
Keyword(s):  
Temperature Dependence ◽  
Rate Constants ◽  
Elemental Sulfur ◽  
Reaction Medium ◽  
Point Of View ◽  
Constant Rate ◽  
Continuous Stream ◽  
Kinetics Of ◽  
Reaction In Solution ◽  
Vulcanization Accelerator

Abstract The investigation of the reaction of sulfur with mercaptobenzothiazole (MBT) is of great interest from the point of view of clarifying the mechanism of the action of the latter as a vulcanization accelerator. We studied the reaction of MBT with elemental sulfur in the melt and in solvent media—vaseline oil and xylene. The course of the reaction was followed by means of the H2S liberated, which was removed from the reaction medium by a continuous stream of nitrogen and was absorbed in a solution of CdCl2. In Figure 1 are presented the kinetics of the liberation of H2S on heating the mixture in a medium of vaseline oil, the concentration of MBT and sulfur comprising, respectively, 0.06 mole/liter and 0.655 g-atom/liter. This ratio and concentration of reactants corresponds to those in the vulcanization of rubber. As can be seen, the splitting out of H2S under the stated conditions proceeds at a constant rate, which can be explained by the very insignificant change in concentrations of reactants over the entire time (only 1.5% of the MBT introduced reacted in 10 hours at 140°). The kinetics of the liberation of H2S from a melt of MBT and sulfur at 140° practically coincide with the kinetics of the reaction in solution (see Figure 1). The temperature dependence of the rate constants leads to the expression K=3.54⋅1010e33500/RT.

Kinetics and Temperature Dependence of the Hydration of NO+ in the Gas Phase

1973 ◽  
Vol 51 (3) ◽  
pp. 456-461 ◽  
Author(s):  
Margaret A. French ◽  
L. P. Hills ◽  
P. Kebarle
Keyword(s):  
Temperature Dependence ◽  
Gas Phase ◽  
Rate Constants ◽  
Room Temperature ◽  
Transfer Reaction ◽  
Negative Temperature ◽  
Ion Source ◽  
Third Order ◽  
The Third ◽  
Kinetics Of

The kinetics of the atmospherically important hydration sequence: NO+(H2O)n−1 + H2O = NO+(H2O)n and the transfer reaction NO+(H2O)n + H2O = HNO2 + H+(H2O)n were examined in nitrogen containing small quantities of NO and H2O with a pulsed high pressure ion source mass spectrometer. The room temperature mechanism and rate constants were found to be in agreement with earlier work in other laboratories. The temperature dependence of the reaction was examined for the range 27–157 °C. The transfer reaction does not occur at higher temperatures so that the NO+ hydration equilibria for n = 1 and 2 could be measured leading to ΔH1,0 = 18.5 and ΔH2,1 = 16.1 kcal/mol. The third order forward clustering rate constants were found to have negative temperature coefficients.

Zum Mechanismus der Chelatbildung von Ni2⊕-ionen mit α- und β-Hydroxyglutarsäure / Formation Mechanism of Ni- (II) -α- and -β-hydroxyglutarate-Complexes

1971 ◽  
Vol 26 (4) ◽  
pp. 299-304 ◽  
Author(s):  
Η. Hoffmann ◽  
U. Nickel
Keyword(s):  
Formation Mechanism ◽  
Rate Constants ◽  
Ring Closure ◽  
Hydroxyl Group ◽  
Pressure Jump ◽  
Rate Determining Step ◽  
Kinetics Of

The kinetics of the formation and dissociation of Ni- (II) -complexes of glutarate, 2-hydroxyglutarate, and 3-hydroxyglutarate were investigated by a pressure jump method. The sequence of the steps in the chelation process for the ligands 2- and 3-hydroxyglutarate, respectively, were evaluated and the rate constants for the specific steps were determined.The results show the chelation to start with formation of a Ni-carboxylate bond and to end with the coordination of the hydroxyl group. In both systems the rate determining step in the chelation process is the ring closure and not the formation of the first bond.

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