Synthesis and Kinetics of Isomerization of mer and fac[CoCO3(en)(Amino Acidato)] Isomers

1995 ◽  
Vol 60 (6) ◽  
pp. 983-989
Author(s):  
Pavel Tyle ◽  
František Jursík
Keyword(s):  
Aqueous Solution ◽  
Rate Constants ◽  
Chelate Ring ◽  
Equilibrium Constants ◽  
Total Rate ◽  
Temperature Dependent ◽  
Kinetics Of

Reaction of [CoXY(en)(AB)]n+ (AB = glycinato or (S)-α-alaninato anion, X = H2O, Y = Cl; AB = (S)-valinato anion, X = Y = Cl) with HCO-3) or Ag(2CO)3 gives mixture of mer- and fac-[CoCO(3(en)(AB)] isomers, ratio of which is temperature dependent. Both isomers undergo in aqueous solution to spontaneous isomerization which does not occur when carbonato group is replaced by oxalato or malonato one. This suggests that the source of stereolability in these complexes is a strain imposed by the four-membered carbonato chelate ring. The equilibrium constants (K = fac/mer) increase in the order KGly < KVal < KAla. The total rate constants obtained at 45 °C and 55 °C increase in the order kAla < kVal < kGly. λ-mer-[CoCO3(en)(S)-Val)] isomer undergoes at 22 °C racemization at the octahedral centre yielding the mixture of 59% δ and 41% λ isomers.

Kinetics and mechanism of gold(III) incorporation into tetrakis(1-methylpyridium-4-yl)porphyrin in aqueous solution

2004 ◽  
Vol 08 (11) ◽  
pp. 1269-1275 ◽  
Author(s):  
Ahsan Habib ◽  
Masaaki Tabata ◽  
Ying Guang Wu
Keyword(s):  
Aqueous Solution ◽  
Rate Constants ◽  
Kinetic Data ◽  
Ph Dependence ◽  
Equilibrium Constants ◽  
Hydroxyl Group ◽  
Net Charge ◽  
First Order ◽  
Kinetics Of ◽  
Hydrolysis Of

The kinetics of the reaction of the tetrakis(1-methylpyridium-4-yl)porphyrin tetracation, [ H 2( TMPyP )]4+, with gold(III) ions were studied along with equilibria of gold(III) species in aqueous medium at 25°C, I = 0.10 M ( NaNO 3). The equilibrium constants for the formation of [ AuCl 4-n( OH ) n ]- ( n = 0,…,4), defined as β n = [ AuCl 4- n ( OH ) n ]- [ Cl -] n / [ AuCl 4-][ OH -] n were found to be that log β1 = 7.94 ± 0.03, log β2 = 15.14 ± 0.03, log β3 = 21.30 ± 0.05 and log β4 = 26.88 ± 0.05. The overall reaction was first order with respect to each of the total [ Au (III)] and [ H 2 TMPyP 4+]. On the basis of pH dependence on rate constants and the hydrolysis of gold(III), the rate expression can be written as d [ Au ( TMPyP )5+]/ dt = ( k 1[ AuCl 4-] + k2[ AuCl 3( OH )-] + k3[ AuCl 2( OH )2-] + k4[ AuCl ( OH )3-])[ H 2 TMPyP 4+], where k1, k2, k3 and k4 were found to be (2.16 ± 0.31) × 10-1, (6.56 ± 0.19) × 10-1, (1.07 ± 0.24) × 10-1, and (0.29 ± 0.21) × 10-1 M -1. s -1, respectively. The kinetic data revealed that the trichloromonohydroxogold(III) species, [ AuCl 3( OH )]-, is the most reactive. The higher reactivity of [ AuCl 3( OH )]- is explained by hydrogen bonding formation between the hydroxyl group of [ AuCl 3( OH )]- and the pyrrole hydrogen atom of [ H 2( TMPyP )]4+. Furthermore, applying the Fuoss equation to the observed rate constants at different ionic strengths, the apparent net charge of [ H 2( TMPyP )]4+ was calculated to be +3.5.

Ferricyanide Oxidation of Butanol Homogeneously Catalysed by Chlororuthenium Complexes

1979 ◽  
Vol 32 (9) ◽  
pp. 1905 ◽  
Author(s):  
AF Godfrey ◽  
JK Beattie
Keyword(s):  
Aqueous Solution ◽  
Complex Formation ◽  
Linear Dependence ◽  
Rate Constants ◽  
Homogeneous Catalyst ◽  
Basic Solution ◽  
Rate Law ◽  
Kinetics Of ◽  
Solution Estimates ◽  
Butanol Concentration

The oxidation of butan-1-ol by ferricyanide ion in alkaline aqueous solution is catalysed by solutions of ruthenium trichloride hydrate. The kinetics of the reaction has been reinvestigated and the data are consistent with the rate law -d[FeIII]/dt = [Ru](2k1k2 [BuOH] [FeIII])/(2k1 [BuOH]+k2 [FeIII]) This rate law is interpreted by a mechanism involving oxidation of butanol by the catalyst (k1) followed by reoxidation of the catalyst by ferricyanide (k2). The non-linear dependence of the rate on the butanol concentration is ascribed to the rate-determining, butanol-independent reoxidation of the catalyst, rather than to the saturation of complex formation between butanol and the catalyst as previously claimed. Absolute values of the rate constants could not be determined, because some of the ruthenium precipitates from basic solution. With K3RuCl6 as the source of a homogeneous catalyst solution, estimates were obtained at 30�0�C of k1 = 191. mol-1 s-1 and k2 = 1�4 × 103 l. mol-1 s-1.

scholarly journals Rates and equilibrium constants for the covalent hydration of 5-bromo-2(1H)-pyrimidinone in aqueous solution

1986 ◽  
Vol 64 (6) ◽  
pp. 1267-1272 ◽  
Author(s):  
Oswald S. Tee ◽  
Jana Pika ◽  
M. Judith Kornblatt ◽  
Michael Trani
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Title Compound ◽  
Equilibrium Constants ◽  
Kinetic Studies ◽  
Kinetics Of

The kinetics of bromination of the title compound (1) have been measured in aqueous solutions of pH 0–6. The change in the order of reaction which occurs around pH 2.5 is explained by 1 reacting via its covalent hydrate, 3. Furthermore, there is sufficient 3 present at equilibrium that the kinetics of its equilibration with 1 were also measured. From these two studies the extent of covalent hydration of 1 is estimated to be 5%.Kinetic studies of the bromination of the dimethyl cation 5 and of its equilibration with the pseudobase 6 were also carried out for the purposes of comparison.The present results for 1, 3, 5, and 6 are compared to earlier results for 2-pyrimidinone and analogous derivatives.

Stability of the Nerve Gas Antidote BIS (4-Hydroxyiminomethyl-1-Pyridinomethyl) Ether Dichloride (Toxogonin®)

1968 ◽  
Vol 2 (9) ◽  
pp. 234-243 ◽  
Author(s):  
Inga Christenson
Keyword(s):  
Aqueous Solution ◽  
Hydrochloric Acid ◽  
Sodium Hydroxide ◽  
Rate Constants ◽  
Kinetics Of Hydrolysis ◽  
Dilute Aqueous Solution ◽  
Nerve Gas ◽  
Ph Range ◽  
Kinetics Of ◽  
Hydrolysis Of

The products and kinetics of hydrolysis of the nerve gas antidote bis(4-hydroxyiminomethyl - 1 - pyridinemethyl) ether dichloride (Toxogonin ®) have been investigated. A survey of these studies is given: The hydrolytic reactions were studied in the pH range 1 M hydrochloric acid to 1 M sodium hydroxide at 25, 45, 75 and 85° C. Rate constants were determined in dilute aqueous solution, generally with an initial Toxogonin concentration of 0.01 mg per ml. In addition, a report is given concerning two-year storage of 25 percent (w/v) Toxogonin solutions at pH 2.5, 3.0 and 3.5. The solutions were stored in glass or polypropylene ampuls at 5, 15, 25 and 45°C. At 5 and 15C° decomposition was negligible, at 25 and 45 °C average decomposition was 1.5 percent and 3.3 percent, respectively.

The retroaldol reaction of 3-methyl-2-butenal

1983 ◽  
Vol 61 (1) ◽  
pp. 171-178 ◽  
Author(s):  
J. Peter Guthrie ◽  
Brian A. Dawson
Keyword(s):  
Sodium Hydroxide ◽  
Equilibrium Constant ◽  
Rate Constants ◽  
Equilibrium Constants ◽  
Aqueous Sodium Hydroxide ◽  
Initial Increase ◽  
Aqueous Sodium ◽  
Rate Determining Step ◽  
Kinetics Of

In aqueous sodium hydroxide solutions at 25 °C, 3-methyl-2-butenal, 1c, undergoes retroaldol cleavage to acetone and acetaldehyde. The kinetics of the retroaldol reaction were followed spectrophotometrically at 242 nm and showed simple first order behavior. When 3-methyl-3-hydroxybutanal, 2c, was added to aqueous sodium hydroxide solutions at 25 °C, there was an initial increase in absorbance at 242 nm, attributed to formation of 1c, followed by a 20-fold slower decrease; the rate of the slow decrease matches the rate of disappearance of 1c under the same conditions. Analysis of the kinetics allows determination of the three rate constants needed to describe the system: khyd = 0.00342; kdehyd = 0.00832; kretro = 0.0564; all M−1 s−1. The equilibrium constant for enone hydration is 0.41. Rate constants for the analogous reactions for acrolein and crotonaldehyde could be obtained from the literature. There is a reasonable rate–equilibrium correlation for the retroaldol step. For the enone hydration step, rate and equilibrium constants respond differently to replacement of hydrogen by methyl. It is proposed that this results from release of strain after the rate-determining step by rotation about a single bond; this decrease in strain is reflected in the equilibrium constant but not in the rate constant.

scholarly journals ACETONE HYDRATION KINETICS AND EVALUATION OF INPUT OF 2-PROPANOL DEHYDRATION REACTION ON RANEY NICKEL UNDER HYDROGENATION CONDITIONS

2018 ◽  
Vol 59 (1) ◽  
pp. 14
Author(s):  
Yu.E. Romanenko ◽  
A.A. Merkin ◽  
O.V. Lefedova
Keyword(s):  
Aqueous Solution ◽  
Kinetic Model ◽  
Raney Nickel ◽  
Rate Constants ◽  
Dehydration Reaction ◽  
Hydrogenation Rate ◽  
Hydration Kinetics ◽  
Skeletal Nickel ◽  
Kinetics Of ◽  
Acetone Hydrogenation

The problem of kinetics of skeletal nickel samples saturation with hydrogen in an aqueous solution of 2-propanol of azeotropic composition was discussed. 2-propanol dehydrogenation and acetone hydrogenation rate constants were calculated. Kinetic model of processes under study was offered.

Kinetics of the photochemical reactions of the croconate dianion in aqueous solution

1992 ◽  
Vol 70 (1) ◽  
pp. 135-143 ◽  
Author(s):  
B Zhao ◽  
M. H. Back
Keyword(s):  
Aqueous Solution ◽  
Electron Transfer ◽  
Quantum Yield ◽  
Rate Constants ◽  
Photochemical Reactions ◽  
Electron Acceptors ◽  
Basic Solution ◽  
Hydroxyl Ion ◽  
Kinetics Of

The kinetics of the photochemical reactions of the dianion of croconic acid (1,2-dihydroxycyclopentenetrione) have been studied in aqueous solution in the presence of electron acceptors. In neutral solutions the quantum yield for disappearance of croconate dianion was small (< 10−3) but was substantially increased in basic solution and in the presence of electron acceptors. At pH 12 in the presence of 4-nitrobenzylbromide and biacetyl a quantum yield of 1 was obtained. The kinetics of the rate of disappearance of croconate dianion as a function of pH and concentration of acceptor showed that the excited dianion is oxidized by acceptors and reacts with hydroxyl ion. A mechanism is proposed that, by assuming reasonable values for the rate constants involved, is shown to be consistent with the results. Keywords: photolysis, kinetics, croconate dianion, electron transfer.

scholarly journals The Kinetics of the Reaction C2H5• + HI → C2H6 + I• over an Extended Temperature Range (213–623 K): Experiment and Modeling

2015 ◽  
Vol 229 (10-12) ◽  
Author(s):  
Nicholas Leplat ◽  
Jozef Federič ◽  
Katarína Šulková ◽  
Mária Sudolská ◽  
Florent Louis ◽  
...  
Keyword(s):  
Rate Constants ◽  
Temperature Dependent ◽  
Temperature Range ◽  
Dependent Rate ◽  
Highly Correlated ◽  
Kinetics Of

AbstractThe present study reports temperature dependent rate constantsHighly correlated

scholarly journals Complex formation between 3;3´-diethylthiacarbocyanine iodide and DNA and its investigation in aqueous solution

1999 ◽  
Vol 1 (1) ◽  
pp. 35-39 ◽  
Author(s):  
M. Y. Anikovsky ◽  
A. S. Tatikolov ◽  
V. A. Kuzmin
Keyword(s):  
Aqueous Solution ◽  
Quantum Yield ◽  
Absorption Spectra ◽  
Flash Photolysis ◽  
Equilibrium Constants ◽  
Intersystem Crossing ◽  
Differential Absorption ◽  
Dna Concentration ◽  
Kinetics Of ◽  
Formation Of Complexes

The binding of 3;3′-diethylthiacarbocyanine iodide (DTCC) with molecules of DNA was investigated by different photochemical methods. Absorption spectra were investigated under various concentration of DNA. Isosbestic points observed in these spectra are attributable to existence of two different complexes DTCC with DNA. Equilibrium constants of the formation of complexes I and II were determined (K1≈106M−1,K2≈5×104M−1accordingly). Differential absorption spectra of two photoisomers of DTCC were obtained by flash photolysis method; it was found that the quantum yield of the short-lived photoisomer decreases and the quantum yield of the second long-lived photoisomer builds up with the increase in the DNA concentration. Kinetics of interaction between the triplet state of the dye and oxygen were investigated under various concentration of DNA. The growth of the quantum yield of fluorescence and intersystem crossing was observed with the increase in the DNA concentration.

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