Nucleophilic square-planar substitutions. II. Substitutions of the bromodiethylenetriamineplatinum(II) complex by pyridine derivatives

1968 ◽  
Vol 21 (12) ◽  
pp. 2873 ◽  
Author(s):  
SC Chan ◽  
FT Wong
Keyword(s):  
Activation Energy ◽  
Rate Constants ◽  
Steric Effects ◽  
Pyridine Derivatives ◽  
Arrhenius Parameters ◽  
Associative Mechanism ◽  
Square Planar ◽  
Inductive Effects ◽  
Two Factors ◽  
Substituted Pyridines

The second-order rate constants for the replacement of coordinated bromide from bromodiethylenetriamineplatinum(11) bromide by a series of pyridine derivatives have been determined over a range of temperatures and the Arrhenius parameters calculated. With the exception of the cyano derivative, replacements of 2-substituted pyridines are considerably slower than those by the corresponding 3- or 4-substituted nucleophiles. This is explicable on the basis of the associative mechanism by invoking steric effects of the substituents. The activation energies for the reaction depend mainly on a combination of two factors, steric and inductive, with the former predominating. These decrease as the position of a given substituent in the nucleophile changes in the order 2, 3, and 4. The inductive effects of the various substituents may be demonstrated with the 4-substituted pyridines, which are sterically similar to the unsubstituted pyridine itself. The methyl substitutent has a small effect, while the cyano and chloro substituents lead to significant increases in activation energy.

The Lewis-acidity of square-planar nickel(II) complexes. III. A kinetic study of the effects of substituents on the addition of 1,10-Phenanthroline to Bis(monothioacetylacetonato)nickel(II) and Bis(dithiophosphato)nickel(II) complexes in toluene

1978 ◽  
Vol 31 (7) ◽  
pp. 1439 ◽  
Author(s):  
MU Fayyaz ◽  
MW Grant
Keyword(s):  
Kinetic Study ◽  
Rate Constants ◽  
Activation Parameters ◽  
Adduct Formation ◽  
Second Order ◽  
Lewis Acidity ◽  
Order Rate ◽  
Measured Rate ◽  
Square Planar ◽  
Inductive Effects

The second-order rate constants and activation parameters for the addition of 1,10-phenanthroline to bis(dialkyldithiophosphato)nickel(II) complexes and substituted bis(monothioacetylacetonato)-nickel(II) complexes in toluene have been measured. Rate constants are in the range 102-108 1. mol-1 s-1 at 25°C, while ΔH‡ is in the range 10-50 kJ mol-1 and ΔS‡ is in the range from -30 to -110 J mol-1 K-1. The higher rate constants, smaller ΔH‡ and more negative ΔS‡ values are associated with complexes with electron- withdrawing substituents. The results are related to the thermo- dynamics of adduct formation, the inductive effects of the substituents and the pKa of the ligands.

REACTION OF OXYGEN ATOMS WITH BUTADIENE

1960 ◽  
Vol 38 (11) ◽  
pp. 2187-2195 ◽  
Author(s):  
R. J. Cvetanović ◽  
L. C. Doyle
Keyword(s):  
Pressure Dependence ◽  
Rate Constants ◽  
Room Temperature ◽  
Relative Rate ◽  
Excess Energy ◽  
General Mechanism ◽  
Arrhenius Parameters ◽  
Heats Of Reaction ◽  
Relative Rate Constants ◽  
Oxygen Atoms

Reaction of oxygen atoms with 1,3-butadiene has been investigated at room temperature. It is found that it conforms to the general mechanism established previously for the analogous reactions of monoolefins. Only 1,2-addition occurs, and the addition products, butadiene monoxide and 3-butenal, possess excess energy when formed as a result of high heats of reaction. The pressure dependence of the formation of the addition products yields the values of the "lifetimes" of the initially produced "hot" molecules. The relative rate constants have been determined at 25 and 127 °C and from these the relative values of the Arrhenius parameters have been calculated.

scholarly journals The Kinetics of Peroxynitrite on Insulin Nitration Damage

2020 ◽  
Author(s):  
Congxiao Zhang ◽  
Fusheng Sun ◽  
Congjiang Zhang ◽  
Yunjing Luo
Keyword(s):  
Activation Energy ◽  
Biological Activity ◽  
Glucose Metabolism ◽  
Rate Constants ◽  
The Body ◽  
Stopped Flow ◽  
Tyrosine Nitration ◽  
Protein Nitration ◽  
Physiological Conditions ◽  
Kinetics Of

Abstract Background: Insulin is one of the most important versatile hormones that is central to regulating the energy and glucose metabolism in the body. There has been accumulating evidence supporting that diabetes was associated with peroxynitrite and protein nitration, and insulin nitration induced by peroxynitrite affected its biological activity. Methods: In this paper, the kinetics of insulin nitration by peroxynitrite in physiological conditions was studied by the stopped flow technique. Results: We determined the values of the reactive rate constants of peroxynitrite decomposition and peroxynitrite-induced tyrosine nitration in the presence of insulin. The activation energy of peroxynitrite decomposition and 3-nitrotyrosine yield in the presence of insulin is 48.8 kJ·mol−1 and 42.7 kJ·mol−1 respectively. Conclusions: It is inferred that the glutamate residue of insulin accelerated peroxynitrite decomposition and tyrosine nitration by reducing the activation energy of reactions. The results could be beneficial for exploring the molecular mechanism of diabetes and offering a new target for diabetes therapies.

scholarly journals KINETICS OF PALM OIL TRANSESTERIFICATION IN METHANOL WITH POTASSIUM HYDROXIDE AS A CATALYST

2010 ◽  
Vol 8 (2) ◽  
pp. 219-225
Author(s):  
Yoeswono Yoeswono ◽  
Triyono Triyono ◽  
Iqmal Tahir
Keyword(s):  
Activation Energy ◽  
Palm Oil ◽  
Rate Constants ◽  
Potassium Hydroxide ◽  
Catalyst Concentration ◽  
Time Interval ◽  
Pseudo First Order Reaction ◽  
Exponential Factor ◽  
Potassium Methoxide ◽  
First Order

A study on palm oil transesterification to evaluate the effect of some parameters in the reaction on the reaction kinetics has been carried out. Transesterification was started by preparing potassium methoxide from potassium hydroxide and methanol and then mixed it with the palm oil. An aliquot was taken at certain time interval during transesterification and poured into test tube filled with distilled water to stop the reaction immediately. The oil phase that separated from the glycerol phase by centrifugation was analyzed by 1H-NMR spectrometer to determine the percentage of methyl ester conversion. Temperature and catalyst concentration were varied in order to determine the reaction rate constants, activation energies, pre-exponential factors, and effective collisions. The results showed that palm oil transesterification in methanol with 0.5 and 1 % w/w KOH/palm oil catalyst concentration appeared to follow pseudo-first order reaction. The rate constants increase with temperature. After 13 min of reaction, More methyl esters were formed using KOH 1 % than using 0.5 % w/w KOH/palm oil catalyst concentration. The activation energy (Ea) and pre-exponential factor (A) for reaction using 1 % w/w KOH was lower than those using 0.5 % w/w KOH.   Keywords: palm oil, transesterification, catalyst, first order kinetics, activation energy, pre-exponential factor

Limitations in Studying the Kinetics of Fabric Detergency

1976 ◽  
Vol 46 (6) ◽  
pp. 459-462 ◽  
Author(s):  
Hans Schott
Keyword(s):  
Rate Constants ◽  
Soil Removal ◽  
Removal Rate ◽  
Fiber Surface ◽  
Natural Soil ◽  
Residual Soil ◽  
Washing Process ◽  
Two Factors ◽  
Surface Irregularities ◽  
Particulate Soil

The simplest expressions for the rate of removal of particulate soil from fabrics, including those for first-order kinetics, are described. Two factors militate against obtaining proportionality constants between a time function and a residual soil function which remain constant for long washing times, namely: redeposition, and heterogeneities in soil and fabric. Soil redeposition tends to lower the observed soil-removal rate. This effect can be eliminated by suitable experimental procedures. However, the inhomogeneities inherent in fabrics (fiber surface irregularities, variation in spaces between fibers and yarns) cause them to have sorption sites with a broad range of soil binding strengths. Variations in the size and shape of particles on artificial test fabrics and, for natural soil, in chemical composition as well, cause the particles to adhere to fabric substrates with bonds of different strengths. These heterogeneities produce a broad range of specific soil-removal rates whose values depend on the energies of adhesion of the particle-fabric complex. The most loosely held soil, with the highest removal rate constants, is washed off early so that the soil remaining on the fabric becomes progressively richer in the most tightly bound soil, with the smallest removal rate constants. Hence the average or observed rate constant for soil removal decreases during the washing process.

STUDIES ON BIOTHERMOKINETICS MEASUEREMENT OF MULTIPLICATION RATE CONSTANTS AND ACTIVATION ENERGY OF ESCHERICHIA COLI USING MICROCALORIMETER

1987 ◽  
Vol 3 (02) ◽  
pp. 113-115
Author(s):  
Tang Houkuan ◽  
◽  
Xie Changli ◽  
Song Zhaohua ◽  
Qu Songsheng ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Activation Energy ◽  
Rate Constants ◽  
Multiplication Rate

ChemInform Abstract: STERIC EFFECTS IN SUBSTITUTION REACTIONS AND ISOMERISATIONS IN SQUARE PLANAR CARBENE AND DICARBENE COMPLEXES OF RHODIUM(I)

1974 ◽  
Vol 5 (17) ◽  
pp. no-no
Author(s):  
D. J. CARDIN ◽  
M. J. DOYLE ◽  
M. F. LAPPERT
Keyword(s):  
Steric Effects ◽  
Substitution Reactions ◽  
Square Planar

Determination of the rate constants and activation energy of acetaminophen hydrolysis by capillary electrophoresis

2002 ◽  
Vol 29 (5) ◽  
pp. 843-850 ◽  
Author(s):  
Gang Chen ◽  
Jiannong Ye ◽  
Huimin Bao ◽  
Pengyuan Yang
Keyword(s):  
Activation Energy ◽  
Capillary Electrophoresis ◽  
Rate Constants
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