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.

Biosorption of Lignin Compounds Using Biomass Derived from Eichhornia crassipes: Batch Studies

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Renganathan Sahadevan ◽  
Ajit Balaji Kannavadi Devaraj ◽  
Dharmendira Kumar Mahendradas ◽  
Baskar Gurunathan ◽  
Manickam Velan
Keyword(s):  
Rate Equation ◽  
Eichhornia Crassipes ◽  
Second Order ◽  
Isotherm Model ◽  
Batch Studies ◽  
First Order ◽  
Order Rate ◽  
Pseudo Second Order ◽  
Pseudo First Order ◽  
Order Rate Equation

Biosorption of lignin compounds by the Eichhornia crassipes was investigated in batch studies. Batch experiments were conducted to study the effect of initial sorbent dosage, solution pH and lignin compounds concentration. Langmuir and Freundlich adsorption isotherm models were used to represent the equilibrium data. The Freundlich isotherm model was found to be fitted very well with the experimental data when compared to Langmuir isotherm model. The results showed that the equilibrium uptake capacity was found to be increased with decrease in biomass dosage. The lignin compound removal was influenced by the initial lignin compounds concentration. The sorption results were analysed for pseudo first order and pseudo second order kinetic model. It was observed that the kinetic data fitted very well with the pseudo second order rate equation when compared to the pseudo first order rate equation. Sorption results were analyzed for the intra particle diffusion model.

cis-Activation by Oxyanions Coordinated to Chromium(III): Aquation and Base Hydrolysis of Nitratopentaamminechromium(III) Ion

1974 ◽  
Vol 52 (4) ◽  
pp. 527-535 ◽  
Author(s):  
Giovanni Guastalla ◽  
Thomas Wilson Swaddle
Keyword(s):  
Reaction Rate ◽  
Base Hydrolysis ◽  
Alkaline Solutions ◽  
Acidic Solutions ◽  
First Order ◽  
Order Rate ◽  
Rate Of Hydrolysis ◽  
Pseudo First Order ◽  
Hydrolysis Of

The aquation of Cr(NH3)5NO32+ in acidic solutions yields not only Cr(NH3)5OH23+ (33%) but also more highly aquated species including cis-Cr(NH3)4(OH2)23+ and Cr(NH3)3(OH2)33+. In 0.1 M HClO4, several successive reactions of comparable rates are involved, but at pH 6 only the two competing initial reactions producing Cr(NH3)5OH2+ and cis-Cr(NH3)4(OH)NO3+ are rate-controlling, so that the overall reaction rate is first-order in substrate with the apparent parameters kA = 2.4 × 10−3 s−1(25°), ΔHA* = 20.4 kcal mol−1, and ΔSA* = −2.1 cal deg−1 mol−1. In alkaline solutions, the pseudo-first-order rate of hydrolysis at a given [OH−] is governed by kobs = kA + kOH [OH−], with kOH = 1.1 × 10−2 M−1 s−1 (25°), ΔHOH* = 25.2 kcal mol−1, and ΔSOH* = 17.0 cal deg−1 mol−1. The path characterized by kOH leads exclusively to Cr(NH3)5OH2+. In both aquation and base hydrolysis, it is the Cr—ONO2 bond that is broken. The production of more highly aquated species in the aquation reactions is attributed to transient chelation of NO3− at the expense of a ligand cis to it. The evidence for this mechanism, and for its operation when oxyanions other than nitrate are coordinated to Cr(III), is reviewed.

scholarly journals Studies on Metal Hydroxy Compounds. XIV. Thermal Analyses, Calorimetry, and Decomposition Kinetics of Heterocationic Hydroxy Chloride Compounds

1973 ◽  
Vol 51 (23) ◽  
pp. 3882-3888 ◽  
Author(s):  
Ah-Dong Leu ◽  
Palepu Ramamurthy ◽  
Etalo A. Secco
Keyword(s):  
Thermal Decomposition ◽  
Rate Equation ◽  
Thermal Analyses ◽  
General Pattern ◽  
Type Equation ◽  
First Order ◽  
Order Rate ◽  
Kinetics Of ◽  
Order Rate Equation ◽  
Initial Mode

Studies were carried out on two series of mixed metal hydroxy chloride compounds of the type xMe(OH)2•yMCl2 where Me = Cd, Cu and M = Mn, Co, Ni, Cu, Zn, Cd, Mg, or Ca.Thermal analyses for the Cd–M series reveal that the initial mode of decomposition involves a dehydroxylation step with a concomitant metathetical reaction between MCl2 and CdO. The compound CdCl2•2CdO is formed and decomposes at higher temperature leading to the eventual volatilization of CdCl2. The kinetics of thermal decomposition follow a simple first-order rate equation. The sole exception to this general pattern of behavior is the Cd–Zn compound.The initial mode of thermal decomposition of the Cu–M series compounds follows a parallel pattern described for the Cd–M series. The kinetic data for the Cu–M series are fitted into three groups: (i) phase boundary control embracing the contracting sphere and contracting plate model equations, (ii) A-E type equation with n = 2, and (iii) first-order rate equation.

Kinetics and mechanism of the base hydrolysis of some trans-dihalogeno(cyclam)rhodium(III) complexes

1978 ◽  
Vol 56 (5) ◽  
pp. 709-713 ◽  
Author(s):  
H. L. Chung ◽  
E. J. Bounsall
Keyword(s):  
Rate Constants ◽  
Activation Parameters ◽  
The Other ◽  
Base Hydrolysis ◽  
Trans Effect ◽  
First Order ◽  
Class B ◽  
Pseudo First Order ◽  
Hydrolysis Of ◽  
Kinetic Class

The base hydrolysis of trans-[Rh(cyclam)XY]+ (cyclam = 1,4,8,11-tetraazacyclotetradecane; X− and Y− = Cl−, Br−, and I−) are studied in aqueous solution over a range of OH− concentration and at various temperatures. The kinetics are done at a constant ionic strength with excess of [OH−] (smallest ratio = 200:1) so that pseudo first order rate constants are obtained for all the determinations. All of the reactions proceed with complete retention of configuration, and no trans-to-cis isomerization is found. The kinetic trans effect of these complexes is I− > Br− > Cl− on a rate basis, but based on ΔH≠, I− > Br− = Cl−. These Rh(III) complexes exhibit kinetic class (b) character on the ΔH≠ basis. The results of the rate constants and the activation parameters are interpreted in ternis of an SN1CB mechanism. The behavior of these complexes is compared to that of the other analogous complexes.

Kinetics of hydrolysis of aromatic bicycling disulfonyl dichlorides

1988 ◽  
Vol 66 (12) ◽  
pp. 3056-3059 ◽  
Author(s):  
Przemysław Sanecki ◽  
Edward Rokaszewski
Keyword(s):  
Rate Constants ◽  
Polarographic Method ◽  
First Order ◽  
Order Rate ◽  
Kinetics Of Hydrolysis ◽  
Consecutive Reactions ◽  
Pseudo First Order ◽  
Kinetics Of ◽  
Hydrolysis Of

Hydrolysis of 16 compounds ClO2S—Ar—B—Ar—SO2Cl (B, bridge) in 20% H2O, 80% v/v CH3CO2H, 0.5 mol dm−3 CH3CO2Na at 298.15 K has been investigated by a polarographic method. From plots of the hydrolysis, pseudo-first-order rate constants for two consecutive reactions [Formula: see text] have been computed and the influence of -SO2Cl groups, bridges B, and SO3− groups on the reactivity of -SO2Cl groups has been discussed. The ratio of rate constants k2/k1 ranges from 0.45 to 30, depending on the structure. Log (k1/(2kH)) correlated linearly with [Formula: see text] and log (k2/k1) correlated linearly with ΔpK for the analogous diamine series H2N—Ar—B—Ar—NH2.

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).

THE REDUCTION OF CYTOCHROMEcBY HYDROQUINONE

1963 ◽  
Vol 41 (1) ◽  
pp. 231-237 ◽  
Author(s):  
G. R. Williams
Keyword(s):  
Reaction Mechanism ◽  
Ionic Strength ◽  
Rate Equation ◽  
Second Order ◽  
Order Rate ◽  
Ferricytochrome C ◽  
Kinetics Of ◽  
Kinetics Of Reduction ◽  
Order Rate Equation

The kinetics of reduction of ferricytochrome c by hydroquinone have been studied. The reaction does not conform to a simple second-order rate equation and it is demonstrated that the deviations are brought about by the presence of p-quinone, one of the products of the reaction. The accelerating effect of p-quinone is explained tentatively on the basis of an involvement of the semi-quinone. The effects on the reaction of pH, ionic strength, and temperature are reported and used to suggest features of the reaction mechanism.

Kinetics of reconstitution of apotyrosinase by copper

1990 ◽  
Vol 68 (2) ◽  
pp. 476-479
Author(s):  
Donald C. Wigfield ◽  
Douglas M. Goltz
Keyword(s):  
Rate Constant ◽  
Copper Concentration ◽  
Copper Ions ◽  
Copper Ion ◽  
Order Rate Constant ◽  
First Order ◽  
Order Rate ◽  
Pseudo First Order ◽  
Rate Limiting ◽  
Kinetics Of

The kinetics of the reconstitution reaction of apotyrosinase with copper (II) ions are reported. The reaction is pseudo first order with respect to apoenzyme and the values of these pseudo first order rate constants are reported as a function of copper (II) concentration. Two copper ions bind to apoenzyme, and if the second one is rate limiting, the kinetically relevant copper concentration is the copper originally added minus the amount used in binding the first copper ion to enzyme. This modified copper concentration is linearly related to the magnitude of the pseudo first order rate constant, up to a copper concentration of 1.25 × 10−4 M (10-fold excess), giving a second order rate constant of 7.67 × 102 ± 0.93 × 102 M−1∙s−1.Key words: apotyrosinase, copper, tyrosinase.

Evidence for the formation of lignin-hexenuronic acid-xylan complexes during modified kraft pulping processes

Holzforschung ◽  
2006 ◽  
Vol 60 (2) ◽  
pp. 137-142 ◽  
Author(s):  
Zhi-Hua Jiang ◽  
Jean Bouchard ◽  
Richard Berry
Keyword(s):  
Acid Hydrolysis ◽  
Kraft Pulp ◽  
Kraft Pulping ◽  
Order Kinetic ◽  
Kraft Pulps ◽  
First Order ◽  
Pseudo First Order ◽  
Hexenuronic Acid ◽  
Kinetics Of ◽  
Hydrolysis Of

Abstract The finding that hexenuronic acid (HexA) groups can be selectively removed from kraft pulps by acid hydrolysis has provided an opportunity to reduce bleaching chemicals. However, there is evidence that the acid hydrolysis is not uniform. In this report, we evaluate the kinetics of acid hydrolysis of HexA in a xylan sample enriched with HexA, a conventional kraft pulp, and three modified kraft pulps: anthraquinone pulp (Kraft-AQ), polysulfide pulp (PS), and polysulfide-anthraquinone pulp (PS-AQ). We found that HexA present in the xylan and conventional kraft pulp behaved similarly toward the acid hydrolysis throughout. On the other hand, HexA present in the Kraft-AQ, PS-AQ and PS pulps was heterogeneous toward acid hydrolysis and the reaction can be separated into two pseudo-first-order kinetic phases, each of which has a different rate constant. The kinetic data provide evidence for the formation of lignin-HexA-xylan complexes during modified kraft pulping processes.

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.

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