Large salt effects and ion pairing in trifluoroacetolysis forming destabilized delocalized benzylic carbocations. Kinetic analysis of the Winstein special salt effect

1993 ◽  
Vol 115 (22) ◽  
pp. 10091-10096 ◽  
Author(s):  
Annette D. Allen ◽  
Thomas T. Tidwell ◽  
Oswald S. Tee
Keyword(s):  
Kinetic Analysis ◽  
Salt Effect ◽  
Ion Pairing ◽  
Salt Effects

Kinetic salt effects in the hydrolysis of ethyl malonate, methyl glutarate and ethyl adipate semiesters

1986 ◽  
Vol 51 (12) ◽  
pp. 2781-2785 ◽  
Author(s):  
M. Martín Herrera ◽  
J. J. Maraver Puig ◽  
F. Sánchez Burgos
Keyword(s):  
Salt Effect ◽  
Alkaline Media ◽  
Salt Effects ◽  
Coulombic Interaction ◽  
Hydroxide Ion ◽  
Ethyl Malonate ◽  
Hydrolysis Of

A study is made on the kinetic salt effect on the reaction of hydrolysis of several charged esters in alkaline media. The results are interpreted on the basis of the coulombic interaction, the salting in of hydroxide ion and a third component depending on size of the substrate.

scholarly journals Kinetic analysis of salt effect on photoamination of phenanthrene via exciplex intermediate.

1989 ◽  
pp. 1292-1298 ◽  
Author(s):  
Masahide YASUDA ◽  
Yoriaki MATSUZAKI ◽  
Toshiaki YAMASHITA ◽  
Kensuke SHIMA
Keyword(s):  
Kinetic Analysis ◽  
Salt Effect

The salt effect on the yields of trioxane in reaction solution and in distillate

RSC Advances ◽  
2015 ◽  
Vol 5 (47) ◽  
pp. 37697-37702 ◽  
Author(s):  
Liuyi Yin ◽  
Yufeng Hu ◽  
Xianming Zhang ◽  
Jianguang Qi ◽  
Weiting Ma
Keyword(s):  
Sulfuric Acid ◽  
Salt Effect ◽  
Salt Effects ◽  
Reaction Solution ◽  
Acid Catalyzed

The salt effects and the mechanisms that govern such effects on the sulfuric acid catalyzed synthesis of trioxane are reported.

Abnormal salt effects on a cation/anion reaction. An interpretation based on the analysis of the components of the experimental rate constant

2009 ◽  
Vol 74 (4) ◽  
pp. 627-641
Author(s):  
Francisco Sánchez ◽  
Pilar Perez-Tejeda ◽  
Rafael Jimenez ◽  
Isaac Villa
Keyword(s):  
Electron Transfer ◽  
Salt Effect ◽  
Transfer Reactions ◽  
Forward Reaction ◽  
Salt Effects ◽  
Experimental Rate ◽  
Asymmetric Behavior ◽  
Negative Effect ◽  
Kinetics Of ◽  
Charge Sign

Salt effects (NaNO3) on the kinetics of the reactions [Fe(CN)6]3– + [Ru(NH3)5(pyz)]2+ = [Fe(CN)6]4– + [Ru(NH3)5(pyz)]3+ (pyz = pyrazine) were studied through T-jump measurements. An abnormal (positive) salt effect on the forward reaction was observed and a normal (negative) effect on the reverse one. These facts imply an asymmetric behavior of anion/cation reactions depending on the charge sign of the oxidant and reductant. The results can be rationalized by using the Marcus–Hush treatment for electron-transfer reactions after decomposition of the experimental rate constants into their components.

The ion-pair mechanism and bimolecular displacement at saturated carbon. VII. Racemization of substituted 1-phenylbromoethanes; ionic strength effects

1989 ◽  
Vol 67 (2) ◽  
pp. 297-304
Author(s):  
Allan R. Stein
Keyword(s):  
Ionic Strength ◽  
Rate Constant ◽  
Salt Effect ◽  
Ion Pairs ◽  
Tetrabutylammonium Bromide ◽  
Ion Pair ◽  
Nucleophilic Attack ◽  
Unimolecular Reaction ◽  
Salt Effects ◽  
Bromide Ion

No, or at most very small, salt effects have been detected for second-order racemizations of various 1-phenylbromoethanes, confirming that the "mixed kinetics", previously reported for 4-methyl- and 3,4-dimethylphenylbromoethanes with tetrabutylammonium bromide in acetonitrile and nitromethane, did not reflect a salt effect on a unimolecular reaction. Thus the uni- and bimolecular rate components can be evaluated using the equation:[Formula: see text]where k1 = first-order or unimolecular rate constant, the intercept, and [Formula: see text], the latter being the rate constant for the bimolecular substitution. A "special salt effect" was found for the unimolecular component; it was especially pronounced for 3,4-dimethyl substrate in acetonitrile with Bu4NClO4 as the electrolyte. In acetone, where no unimolecular reaction component was detected even with those substrates giving the most stable carbocations, the only salt effect was a common ion, Bu4N+, effect on the incomplete dissociation of Bu4NBr. From an iterative best fit for plots of observed rate versus calculated bromide ion activity for unsubstituted, 4-methyl, and 3,4-dimethyl substrates, Kassoc ~ 15 ± 1 at 40 °C. The results are interpreted as additional support for a progression of mechanism with nucleophilic attack possible at any stage of the series of equilibria: substrate [Formula: see text] contact ion pair [Formula: see text] various solvated ion pairs [Formula: see text] dissociated ions. Keywords: special salt effects, ionic strength effects, racemization of 1-phenylbromoethanes, mechanism of nucleophilic substitution, ion pair mechanism.

Nature of Salt Effects and Mechanism of Covalent Bond Heterolysis

2007 ◽  
Vol 32 (2) ◽  
pp. 73-118 ◽  
Author(s):  
Genrih F. Dvorko ◽  
Engelsine A. Ponomareva ◽  
Mykola E. Ponomarev ◽  
Mikhailo V. Stambirsky
Keyword(s):  
Transition State ◽  
Salt Effect ◽  
Ion Pairs ◽  
Covalent Bond ◽  
Organic Substrates ◽  
Reaction Products ◽  
Salt Effects ◽  
Hsab Principle ◽  
Limiting Step ◽  
Acids And Bases

Data on the influence of neutral salts on the rates of unimolecular heterolyses of organic substrates, obtained mainly by the verdazyl method, are summarized here. It is assumed that heterolysis takes place with consecutive formation of four ion pairs: contact (CIP), cavity-separated (CSIP), one solvent moleculeseparated (SIP) and solvent-separated (SSIP). [Formula: see text] In the limiting step, the CIP interacts with a solvent cavity and the CSIP is formed, which converts quickly into the SIP and subsequently to the SSIP, which also quickly gives the reaction products. In the transition state, bonds between the molecules solvating the CIP are broken. In the absence of salt, the return from external ion pairs does not have much importance. The verdazyl indicator quickly and quantitatively reacts with the SSIP. The normal salt effect takes place due to the action of salt on the covalent substrate, which catalyses CIP formation. The special salt effect is caused by the association of the salt with the CIP, which prolongs the lifetime of the intermediate and increases the probability of its contact with a solvent cavity. The negative special salt effect is caused by association of the salt with the SIP or SSIP, which prolongs the lifetime of the intermediates and increases the probability of their contact with a solvent cavity to return to the covalent substrate. When the salt reacts with the SIP, the salt effect does not depend on the concentration and nature of verdazyl, but such a dependence takes place when the salt reacts with the SSIP. The site of the action of the salt is determined by the Hard and Soft Acids and Bases (HSAB) principle.

Metallic Salt Effect on Polymer Oxidation

1952 ◽  
Vol 44 (3) ◽  
pp. 444-444
Author(s):  
N Chalapathi Rao ◽  
Hugh Winn ◽  
J Shelton
Keyword(s):  
Salt Effect ◽  
Metallic Salt ◽  
Polymer Oxidation

Kinetic Aspects of the Interaction of Blood Clotting Enzymes

1965 ◽  
Vol 13 (01) ◽  
pp. 155-175 ◽  
Author(s):  
H. C Hemker ◽  
P.W Hemker ◽  
E. A Loeliger
Keyword(s):  
Kinetic Analysis ◽  
Enzyme Kinetics ◽  
Blood Clotting ◽  
Enzyme System ◽  
Enzyme Kinetic ◽  
Clotting Time ◽  
Standard Methods

SummaryApplication of the methods of enzyme-kinetic analysis to the results of clotting tests is feasible and can yield useful results. However, the standard methods of enzyme kinetics are not applicable without modifications imposed by the peculiarities of the blood-clotting enzyme system. The influence of the following complicating circumstances is calculated :1. Substrate is not present in excess.2. Only relative measures exist for concentrations of substrate or enzymes.3. Enzymes and substrates are often added together.4. Reagents are not pure.5. Clotting-time is our only measure for clotting-velocity.Formulas are deduced, which makes it possible to recognize the effect of these complications.

Sign in / Sign up

Export Citation Format

Share Document