Studies in solvolysis. Part VIII. An entropy correlation related to the reaction of various nucleophiles with malachite green

1977 ◽  
Vol 55 (4) ◽  
pp. 686-692 ◽  
Author(s):  
Stephen Harvey Morris ◽  
John Marshall William Scott ◽  
Frederick Steele
Keyword(s):  
Temperature Dependence ◽  
Malachite Green ◽  
Methyl Iodide ◽  
Rate Constants ◽  
Transition States ◽  
Reaction Coordinate ◽  
Similar Correlation ◽  
Displacement Reactions

The entropies of activation related to the reactions of aqueous malachite green with the nucleophiles water, hydroxide, hydrazine, ammonia, hypochlorite, and sulphite have been calculated from the temperature dependence of the rate constants appropriate to these reactions. The entropies of the transition states for these reactions have been characterized and the transition states shown to be 'reactant like'. A similar correlation, based on data for a series of nucleophiles attacking methyl iodide, suggests that the transition states for the SN2 displacement reactions are also 'reactant like' with respect to the attacking nucleophile. A relationship between two distinct parameters each of which is related to the position of transition states along the reaction coordinate is considered.

Temperature Dependence of Disproportionation–Combination Ratios for Alkyl Radicals in Liquid Methane

1971 ◽  
Vol 49 (17) ◽  
pp. 2861-2867 ◽  
Author(s):  
Hugh A. Gillis
Keyword(s):  
Activation Energy ◽  
Temperature Dependence ◽  
Gas Phase ◽  
Rate Constants ◽  
Room Temperature ◽  
Transition States ◽  
Alkyl Radicals ◽  
Liquid Methane ◽  
Ethyl Radicals

The ratios of rate constants for disproportionation to combination have been measured for ethyl radicals and for i-propyl radicals in liquid methane between −181 and −94 °C. The radicals were generated by γ-radiolysis of dilute methane solutions of ethylene-d4 or propylene-d6. The activation energy for combination was found to exceed that for disproportionation by 290 ± 30 cal mol−1 for ethyl radicals and by 255 ± 25 cal mol−1 for i-propyl radicals. In both cases the disproportionation—combination ratio in the liquid, extrapolated to room temperature, is greater than that in the gas phase by a factor of about 2.5. These results are interpreted as indicating that disproportionation and combination reactions proceed by way of different transition states.

13C kinetic isotope effects and reaction coordinate motions in transition states for SN2 displacement reactions

1976 ◽  
Vol 54 (7) ◽  
pp. 1146-1161 ◽  
Author(s):  
Warren Edward Buddenbaum ◽  
Vernon Jack Shiner Jr.
Keyword(s):  
Transition State ◽  
Isotope Effect ◽  
Methyl Iodide ◽  
Isotope Effects ◽  
Transition States ◽  
Kinetic Isotope Effects ◽  
Chloride Ions ◽  
Reaction Coordinate ◽  
Kinetic Isotope ◽  
State Models

Reaction coordinate motions and 13C kinetic isotope effects at 25 °C have been calculated for the SN2 reactions of methyl iodide with iodide, cyanide, and chloride ions and for the SN2 reaction of benzyl bromide with hydroxide ion using transition state models characterized by single interaction force constant, F12, between the bond being formed and the bond being broken. The isotope effect calculations show that the dependence of calculated 13C isotope effects on transition state symmetry found by Willi and Sims etal. holds true for reaction barriers corresponding to small values of νL, while the symmetry dependence observed by Bron holds true for barriers corresponding to large values of νL.νL was also found to have a strong influence on the reaction coordinate motions of the transition states. In particular, for the methyl iodide reactions an increase in νL increases the distortion of the methyl group in the direction expected for a classical SN2 reaction. Finally, reaction coordinate motions were used to show that the model proposed by Bron for the borderline region between SN1 and SN2 reaction mechanisms predicts an increase in the 13C kinetic isotope effect with decreasing total bond order and not the decrease suggested by Bron.

Salt effect in hydrolysis of 3-acyl-1,3-diphenyltriazenes

1981 ◽  
Vol 46 (12) ◽  
pp. 3104-3109 ◽  
Author(s):  
Miroslav Ludwig ◽  
Oldřich Pytela ◽  
Miroslav Večeřa
Keyword(s):  
Sodium Chloride ◽  
Temperature Dependence ◽  
Potassium Chloride ◽  
Rate Constants ◽  
Zinc Sulphate ◽  
Salt Effect ◽  
Sodium Sulphate ◽  
Potassium Sulphate ◽  
Lithium Sulphate ◽  
Hydrolysis Of

Rate constants of non-catalyzed hydrolysis of 3-acetyl-1,3-diphenyltriazene (I) and 3-(N-methylcarbamoyl)-1,3-diphenyltriazene (II) have been measured in the presence of salts (ammonium chloride, potassium chloride, lithium chloride, sodium chloride and bromide, ammonium sulphate, potassium sulphate, lithium sulphate, sodium sulphate and zinc sulphate) within broad concentration ranges. Temperature dependence of the hydrolysis of the substrates studied has been measured in the presence of lithium sulphate within temperature range 20° to 55 °C. The results obtained have been interpreted by mechanisms of hydrolysis of the studied substances.

Radiolysis studies on the corrosion inhibitors 1 -hexyn-3-ol, cinnamonitrile, and 1,3-diethyl-2-thiourea

1995 ◽  
Vol 73 (12) ◽  
pp. 2137-2142 ◽  
Author(s):  
A.J. Elliot ◽  
M.P. Chenier ◽  
D.C. Ouellette
Keyword(s):  
Hydrogen Atom ◽  
Hydroxyl Radical ◽  
Temperature Dependence ◽  
Rate Constant ◽  
Rate Constants ◽  
Corrosion Inhibitors ◽  
Hydrated Electron

In this publication we report: (i) the rate constants for reaction of the hydrated electron with 1-hexyn-3-ol ((8.6 ± 0.3) × 108 dm3 mol−1 s−1 at 18 °C), cinnamonitrile ((2.3 ± 0.2) × 1010 dm3 mol−1 s−1 at 20 °C), and 1,3-diethyl-2-thiourea ((3.5 ± 0.3) × 108 dm3 mol−1 s−1 at 22 °C). For cinnamonitrile and diethylthiourea, the temperature dependence up to 200 °C and 150 °C, respectively, is also reported; (ii) the rate constants for the reaction of the hydroxyl radical with 1-hexyn-3-ol ((5.5 ± 0.5) × 109 dm3 mol−1 s−1 at 20 °C), cinnamonitrile ((9.2 ± 0.3) × 109 dm3 mol−1 s−1 at 21 °C), and diethylthiourea ((8.0 ± 0.8) × 108 dm3 mol−1 s−1 at 22 °C). For cinnamonitrile, the temperature dependence up to 200 °C is also reported; (iii) the rate constant for the hydrogen atom reacting with 1-hexyn-3-ol ((4.3 ± 0.4) × 109 dm3 mol−1 s−1 at 20 °C). Keywords: radiolysis, corrosion inhibitors, rate constants.

scholarly journals On the 3D → 2D Isomerization of Hexaborane(12)

Chemistry ◽  
2021 ◽  
Vol 3 (1) ◽  
pp. 28-38
Author(s):  
Josep M. Oliva-Enrich ◽  
Ibon Alkorta ◽  
José Elguero ◽  
Maxime Ferrer ◽  
José I. Burgos
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Transition States ◽  
Three Dimensional ◽  
Reaction Coordinate ◽  
Intrinsic Reaction Coordinate ◽  
Limiting Factor ◽  
Two Dimensional ◽  
Axis Of Rotation

By following the intrinsic reaction coordinate connecting transition states with energy minima on the potential energy surface, we have determined the reaction steps connecting three-dimensional hexaborane(12) with unknown planar two-dimensional hexaborane(12). In an effort to predict the potential synthesis of finite planar borane molecules, we found that the reaction limiting factor stems from the breaking of the central boron-boron bond perpendicular to the C2 axis of rotation in three-dimensional hexaborane(12).

A kinetic standard for precise calibration of spectrophotometer cell temperature.

1981 ◽  
Vol 27 (5) ◽  
pp. 753-755 ◽  
Author(s):  
P A Adams ◽  
M C Berman
Keyword(s):  
Temperature Dependence ◽  
Rate Constants ◽  
Cell Temperature ◽  
First Order ◽  
Order Rate ◽  
Acid Catalyzed ◽  
Pseudo First Order ◽  
Hydrolysis Of

Abstract We describe a simple, highly reproducible kinetic technique for precisely measuring temperature in spectrophotometric systems having reaction cells that are inaccessible to conventional temperature probes. The method is based on the temperature dependence of pseudo-first-order rate constants for the acid-catalyzed hydrolysis of N-o-tolyl-D-glucosylamine. Temperatures of reaction cuvette contents are measured with a precision of +/- 0.05 degrees C (1 SD).

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