Octahedral cobalt(III) complexes of the chloropentammine type. XX. The preparation, properties, and reactions of some chlorocycloalkylaminebis- (ethylenediamine)cobalt(III) salts

1970 ◽  
Vol 23 (4) ◽  
pp. 707 ◽  
Author(s):  
SC Chan ◽  
TL Cheung
Keyword(s):  
Rate Constants ◽  
Ion Pair ◽  
Base Hydrolysis ◽  
Isomeric Form ◽  
Visible Absorption ◽  
First Order ◽  
Order Rate ◽  
Hydrolysis Of ◽  
Conjugate Base ◽  
Visible Absorption Spectroscopy

Salts of one isomeric form of the chlorocycloalkylaminebis(ethylenediamine)cobalt(111) series of cations have been prepared and characterized. They are tentatively assigned a cis configuration on the basis of visible absorption spectroscopy. The first-order rate constants for the solvolytic aquation of these cations have been determined at 50.5�, and the results suggest the presence of steric acceleration. The second-order rate constants for the base hydrolysis of these cations have also been determined at 0� and ionic strength of 0.1M. These results are discussed in terms of the conjugate-base/ion-pair mechanistic spectrum postulated previously.

Octahedral cobalt(III) complexes of the chloropentammine type. XVIII. Hydrolysis of some Chloroanilinebis(ethylenediamine)cobalt(III) complexes, and a rationalization for the conjugate-base and ion-pair mechanisms

1969 ◽  
Vol 22 (9) ◽  
pp. 1851 ◽  
Author(s):  
SC Chan ◽  
OW Lau
Keyword(s):  
Chloride Ion ◽  
Ion Pair ◽  
Base Hydrolysis ◽  
Methyl Substituent ◽  
Substituted Anilines ◽  
First Order ◽  
Base Mechanism ◽  
Higher Temperature ◽  
Hydrolysis Of ◽  
Conjugate Base

The kinetics for the appearance of chloride ion from aqueous solutions of the cis-chloroanilinebis(ethylenediamine)cobalt(III) cation are determined over the pH ranges of 2-3 at 40.0� and of 8-9 at 0�. By using self-buffered mixtures, the rate constants for the reaction are also measured at 40.0� as a function of the concentration of complex or of free aniline. The results are discussed in terms of the conjugate- base mechanism. A rationalization of this mechanism and the ion-pair mechanism is proposed to incorporate the base hydrolysis of other previously investigated systems where the complexes are decidedly much less acidic. At a higher temperature (65.0�), both chloride ion and aniline are liberated at similar rates, and the process is treated as parallel first-order reactions. By using complexes with meta- and para-substituted anilines, the effect of the methyl substituent on reactivity is studied.

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).

Base hydrolysis of trans-Halogenoamminebis(dimethylglyoximato) (III). Complexes

1969 ◽  
Vol 22 (12) ◽  
pp. 2569 ◽  
Author(s):  
SC Chan ◽  
PY Leung
Keyword(s):  
Equilibrium Constants ◽  
Base Hydrolysis ◽  
Hydroxide Ion ◽  
First Order ◽  
Rate Determining Step ◽  
Rapid Formation ◽  
Pseudo First Order ◽  
Conjugate Bases ◽  
Hydrolysis Of ◽  
Conjugate Base

The disappearance of trans-[Co(LH)2(NH3)X] (LH = dimethylglyoximate ion, X = chloride or bromide) has been studied in aqueous solutions over a range of alkali concentrations at various temperatures. The kinetics were done with excess of hydroxide ion at a constant ionic strength so that pseudo first-order rate constants were obtained in all the runs. The results were interpreted in terms of the rapid formation of a pre- equilibrium species which then reacts in a rate-determining step to give products. The relatively large equilibrium constants support a conjugate-base pre-equilibrium, in which the proton is lost from oxygen, while the relatively low reactivities of the conjugate-bases are consistent with the absence of electropositive electromeric effects. The similarity in the reactivities of the chloro and the bromo conjugate-bases suggests the possibility of an SN2CB mechanism.

scholarly journals Kinetic Evidence for Near Irreversible Nonionic Micellar Entrapment ofN-(2′-Methoxyphenyl)phthalimide (1) under the Typical Alkaline Reaction Conditions

2014 ◽  
Vol 2014 ◽  
pp. 1-6
Author(s):  
M. Niyaz Khan ◽  
Yoke-Leng Sim ◽  
Azhar Ariffin
Keyword(s):  
Kinetic Analysis ◽  
Alkaline Hydrolysis ◽  
Rate Constants ◽  
Total Concentration ◽  
Reaction Conditions ◽  
First Order ◽  
Order Rate ◽  
Alkaline Reaction ◽  
Pseudo First Order ◽  
Hydrolysis Of

The values of pseudo-first-order rate constants (kobs) for alkaline hydrolysis of1, obtained at 1.0 mM NaOH and withinCmEnT(total concentration ofCmEn) range of 3.0–5.0 mM forC12E23and 10–20 mM forC18E20, fail to obey pseudophase micellar (PM) model. The values of the fraction of near irreversibleCmEnmicellar trapped1molecules (FIT1) vary in the range ~0–0.75 forC12E23and ~0–0.83 forC18E20under such conditions. The values ofFIT1become 1.0 at ≥10 mMC12E23and 50 mMC18E20. Kinetic analysis of the observed data at ≥10 mMC12E23shows near irreversible micellar entrapment of1molecules under such conditions.

The Kinetics of Isotope Effects in a Model Solvolysis System Involving One Optically Active Ion Pair Intermediate

1974 ◽  
Vol 52 (10) ◽  
pp. 1937-1941 ◽  
Author(s):  
P. Christian Vogel
Keyword(s):  
Rate Constant ◽  
Rate Constants ◽  
Isotope Effects ◽  
Kinetic Scheme ◽  
Ion Pair ◽  
Rate Equations ◽  
Differential Analysis ◽  
First Order ◽  
Order Rate ◽  
Special Cases

The derivation of the observed first-order rate constants from the "exact" integrated rate equations for the kinetic scheme of reaction 1 is presented. It is shown that the solvolytic exponential first-order rate constant is a special case of the polarimetric rate constant and that the optical activity of the product is determined by a multiplicative ratio of rate constants for the optically important reactions of the ion pair intermediate. A form of the integrated first-order polarimetric rate equation with a linearly independent parameter set is presented. The functions for the first-order rate constants derived using the steady state approximation are special cases of the functions derived from the exact equations, as are the functions for the first-order rate constants for two systems which involve pre-equilibria followed by a slow product forming step. These functions cannot all be derived one from the other. A differential analysis of observed isotope effects as functions of isotope effects on the rate constants for reactions involving the intermediates is presented.

Acyl Transfer Isomerization of Glycerol 1,2-Dibutyrate and Propane-1,2-diol 1-Butyrate

1998 ◽  
Vol 51 (6) ◽  
pp. 455 ◽  
Author(s):  
Charmian J. O'Connor ◽  
Richard H. Barton
Keyword(s):  
Rate Constants ◽  
Equilibrium Mixture ◽  
Acyl Transfer ◽  
Product Mix ◽  
First Order ◽  
Order Rate ◽  
Pregastric Lipase ◽  
Water Ph ◽  
Emulsion Systems ◽  
Hydrolysis Of

The speciation of mixed butyrylglycerols (glycerol butyrates) and propanediol butyrate esters in the product mix from lamb pregastric lipase-catalysed hydrolysis of tributyrylglycerol and propane-1,2-diol dibutyrate has been examined by 13C n.m.r. spectroscopy. Samples from the quenched reaction mixture were extracted and allowed to stand in emulsion systems made up in bis tris propane buffer or water, pH 7·0, and in the absence of enzyme. There is clear evidence of uncatalysed conversion of rac-1,2-dibutyrylglycerol into the 1,3-isomer to form an equilibrium mixture containing c. 60–67% 1,3-isomer, and of conversion of propane-1,2-diol 1-butyrate into propane-1,2-diol 2-butyrate to form an equilibrium mixture containing c. 67% 2-monoester. Conversion kinetics to reach equilibrium are first order. Rate constants for acyl transfer of the diacylglycerol are 0·48 h-1 (in water) and 0·68 h-1 (in buffer) at 50°C, while those for acyl transfer of the 1-monoester are 0·72 h-1 (50°C) and 0·35 h-1 (35°C).

The trans-Effect in Octahedral Complexes. VI. Base Hydrolysis of trans-Hydroxybromo and trans-Hydroxychlorobis(ethylenediamine)-rhodium(III) Complexes

1975 ◽  
Vol 53 (12) ◽  
pp. 1842-1848 ◽  
Author(s):  
Anthony Poë ◽  
Carol Vuik
Keyword(s):  
Rate Equation ◽  
Base Hydrolysis ◽  
Small Contribution ◽  
Trans Effect ◽  
First Order ◽  
Order Rate ◽  
Pseudo First Order ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Order Rate Equation

The kinetics of base hydrolysis of the complexes trans-[Rh(en)2(OH)X]+ (X = Br or Cl) follow the pseudo first order rate equation kobs = k1 + k2[OH−]. The small contribution of the [OH−]-dependent term is due to lower values of ΔS2≠ − ΔS1≠ than are observed for the complexes cis-[Rh(en)2(OH)Cl]+ and [Rh(NH3)5X]2+ (X = Cl, Br, or I ). The values of ΔH1≠ are used to obtain new values of the intrinsickinetictrans-effect (i.k.t.e.) of hydroxide that agree with that determined from aquation of trans.-[Rh(en)2(OH)I]+ and place hydroxide in the i.k.t.e. series [Formula: see text] The new data also allow hydroxide to be placed in a thermodynamic trans-effect (t.t.e.) series I > OH > NH3 > Br > Cl > OH2, and the different position of hydroxide in the two series is discussed.

A Kinetic Oxymoron: Concentration-Dependent First-Order Rate Constants for Hydrolysis of Ceftazidime

1998 ◽  
Vol 87 (1) ◽  
pp. 53-58 ◽  
Author(s):  
Josephine O. Fubara ◽  
Robert E. Notari
Keyword(s):  
Rate Constants ◽  
First Order ◽  
Order Rate ◽  
Hydrolysis Of

Electrochemistry of Ruthenium Ammine Complexes

1975 ◽  
Vol 53 (19) ◽  
pp. 2922-2929 ◽  
Author(s):  
C. M. Elson ◽  
I. J. Itzkovitch ◽  
J. McKenney ◽  
John A. Page
Keyword(s):  
Cyclic Voltammetry ◽  
Rate Constants ◽  
Reduction Step ◽  
Methane Sulfonate ◽  
Ammine Complexes ◽  
Chloro Complexes ◽  
First Order ◽  
Order Rate ◽  
Electron Reduction ◽  
Hydrolysis Of

The electrochemistry of ruthenium(III) penta- and tetraammine chloro complexes has been investigated. In each case, the ruthenium(III) species was found to undergo an initial one electron reduction step, followed by hydrolysis of the chloride(s) in the ruthenium(II) product. The rate constants for the substitution steps were evaluated by cyclic voltammetry. An aqueous 0.30 M methane sulfonate electrolyte of pH 2.0 was used at 25 °C.Values for the reversible "E1/2" (V υs. SCE) and first order rate constants for the (stepwise) replacement of the Cl− are: Ru(NH3)5Cl+, −0.282 V and 17 s−1; cis-Ru(NH3)4Cl2+, −0.328 V, 80 s−1, and 5 s−1; trans-Ru(NH3)4Cl2+, −0.412 V, 2 s−1, and 0.4 s−1.The electrochemistry of Ru(NH3)5SO22+was also investigated. In a 0.10 M CH3SO3H – 0.20 M CH3SO3Na electrolyte the ruthenium(II) species was found to undergo an initial one electron oxidation step with "E1/2" = +0.50 V, followed by a slow hydrolysis of the SO2 in the ruthenium(III) product with k = 2.4 × 10−2 s−1 at 25 °C.

Octahedral cobalt(III) complexes of the chloropentammine type. XIX. The preparation, properties, and reactions of some Chlorobenzylaminebis-(ethylenediamine)cobalt(III) salts and related complexes

1969 ◽  
Vol 22 (9) ◽  
pp. 1869 ◽  
Author(s):  
SC Chan ◽  
OW Lau
Keyword(s):  
Rate Constants ◽  
Open Chain ◽  
First Order ◽  
Benzyl Radical ◽  
Order Rate ◽  
Visible Spectra ◽  
Rate Of Reaction ◽  
Inductive Effects ◽  
Steric Factors ◽  
Hydrolysis Of

Salts of one isomeric series of chlorobenzylaminebis(ethylenediamine)- cobalt-(III) type of cations have been prepared using a variety of benzylamine derivatives as ligands. They are tentatively assigned a cis-configuration on the basis of their visible spectra. The first- order rate constants for their solvolytic aquation have been measured. Both resonance contributions and steric factors from the benzyl radical, as well as inductive effects of its substituents, all have negligibly small influences on the rate of reaction. The second-order rate constants for the hydrolysis of these cations by base have also been determined. The labilizing powers of the benzylamine ligands in this reaction are very similar to those of open-chain aliphatic amines, and significantly different from those of aromatic amines. To see if reactivities depend on the distance of separation between cobalt and the benzene ring, the experiments are extended to the chloro(β- phenylethylamine)bis(ethylenediamine)cobalt(III) type of complexes.

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