Activation entropy as a dominant factor in the oxidative addition of some group IV hydrides to an iridium(I) complex

J. P. Fawcett; J. F. Harrod

doi:10.1139/v76-442

Activation entropy as a dominant factor in the oxidative addition of some group IV hydrides to an iridium(I) complex

Canadian Journal of Chemistry ◽

10.1139/v76-442 ◽

1976 ◽

Vol 54 (19) ◽

pp. 3102-3109 ◽

Cited By ~ 8

Author(s):

J. P. Fawcett ◽

J. F. Harrod

Keyword(s):

Relative Rate ◽

Oxidative Addition ◽

Group Iv ◽

Dominant Factor ◽

Iridium Complex ◽

Activation Entropy ◽

Acid Base ◽

Square Planar ◽

The Difference ◽

Kinetics Of

The kinetics of the reactions[Formula: see text]have been studied (M = Si, Ge, Sn). All three reactions proceed by predissociation of the iridium complex and concerted cis addition of Ph3MH to the square-planar intermediate. The relative rate of addition of Ph3MH increases in the order Si (1) < Ge (18) < Sn (70) and the difference in rate within experimental error is due entirely to change in ΔS0. It is concluded that, for this particular series of oxidative addition reactions, solvation effects related to a change in polarity on passage to the transition state are more important than bond energies, or acid–base properties, in determining relative reaction energetics. The relevance of entropy barriers to the problem of paraffin activation is discussed.

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Theoretical studies of inorganic and organometallic reaction mechanisms. 3. The origin of the difference in the barrier for the kinetic and thermodynamic products for the oxidative addition of dihydrogen to a square-planar iridium complex

Journal of the American Chemical Society ◽

10.1021/ja00028a018 ◽

1992 ◽

Vol 114 (2) ◽

pp. 517-522 ◽

Cited By ~ 35

Author(s):

Andrew L. Sargent ◽

Michael B. Hall ◽

Martyn F. Guest

Keyword(s):

Reaction Mechanisms ◽

Oxidative Addition ◽

Iridium Complex ◽

Theoretical Studies ◽

Square Planar ◽

The Difference

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Acid-Catalyzed Oxidative Addition of a C–H Bond to a Square Planar d8 Iridium Complex

Journal of the American Chemical Society ◽

10.1021/ja503953v ◽

2014 ◽

Vol 136 (25) ◽

pp. 8891-8894 ◽

Cited By ~ 14

Author(s):

Jason D. Hackenberg ◽

Sabuj Kundu ◽

Thomas J. Emge ◽

Karsten Krogh-Jespersen ◽

Alan S. Goldman

Keyword(s):

Oxidative Addition ◽

Iridium Complex ◽

Square Planar ◽

Acid Catalyzed

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Anaerobic degradation kinetics of a cholesteryl ester

Water Science & Technology ◽

10.2166/wst.2003.0379 ◽

2003 ◽

Vol 48 (6) ◽

pp. 141-147

Author(s):

S. Gutiérrez ◽

M. Viñas

Keyword(s):

Palmitic Acid ◽

Anaerobic Degradation ◽

Drop Size ◽

Degradation Kinetics ◽

Relative Rate ◽

Hydrolysis Rate ◽

Order Kinetic ◽

Order Kinetic Model ◽

The Difference ◽

Kinetics Of

The most important components of wool scouring effluent grease are esters of sterols. Cholesteryl palmitate (CP) is the main ester in this grease. In this paper, the influence of the ester concentration in the anaerobic digestion and the relative rate of the different degradation steps, are studied. The experiment was carried out to measure methane production in the anaerobic degradation of acetate, palmitic acid (PA) and CP. A first-order kinetic model was assumed for hydrolysis and Monod models were assumed for both the methanogenic and acetogenic steps. Maximum hydrolysis rate was found to be around 20 times faster than the maximum methanogenic reaction rate during the experience. The lanolin emulsion drop size effect was also evaluated employing fine and coarse stock lanolin emulsions and no adapted sludge. Concentrations of 13.7 to 4.6 gCOD.l-1 were employed. In a previous study, the effect of palmitic acid emulsion size was found important when similar sludge was tested. When esters are degraded, a significant effect of drop size on the degradation rate was not found. The difference between CP and PA emulsions behavior could be due to the fact that cholesterol produced during the ester degradation has a protective effect on the sludge.

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Kinetics of acid-catalyzed hydrolysis of fluorinated propanoates

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19832805 ◽

1983 ◽

Vol 48 (10) ◽

pp. 2805-2811 ◽

Cited By ~ 4

Author(s):

Oldřich Paleta ◽

Jaroslav Kvíčala ◽

Václav Dědek

Keyword(s):

Rate Constants ◽

Relative Rate ◽

Chloride Concentration ◽

Activation Entropy ◽

High Activation ◽

Isokinetic Relationship ◽

Relative Rate Constants ◽

Acid Catalyzed ◽

Kinetics Of ◽

Hydrolysis Of

Rates of hydrolysis, kH+, of methyl 2-chloro-2,3,3,3-tetrafluoro-(III), 2,3-dichloro-2,3,3-trifluoro-(IV), 2,2,3-trichloro-3,3-difluoro-(V), 2,3,3,3-tetrafluoro-(VI) and 3-chloro-2,3,3-trifluoropropanoate (VII) were measured in 0.5M-HCl in aqueous methanol (80% vol; 76% wt) at 40, 50 and 60 °C. The relative rate constants, krel (50 °C), (for the propanoate III, kH+ = 4.3 . 10-5 l mol-1 s-1; krel = 100) are 311, 100, 38, 9.4, 44 and 15 for the esters II, III, IV, V, VI and VII, respectively (experimental error ±9%). It was found that krel = αβ where α and β are the following factors for groups in the position 2 and 3: CClF 10, CHF 4.2, CCl2 2.8, CF3 10 and CClF2 3.6. The rate constants obey the isokinetic relationship. For the ester III the dependence of log kobs on logarithm of hydrogen chloride concentration is linear at concentrations 0.08-2.4 mol l-1 which, together with high activation entropy ΔS≠ for the esters III-VII (-167 to -217 J mol-1 K-1), shows that the hydrolysis proceeds by an AAC2 mechanism.

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The effect of composition of cobalt-molybdenum catalysts on their surface acidity and isomerisation activity

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19800697 ◽

1980 ◽

Vol 45 (3) ◽

pp. 697-702 ◽

Cited By ~ 1

Author(s):

Vlastimil Vyskočil ◽

Miroslav Zdražil

Keyword(s):

Chromatographic Method ◽

Surface Acidity ◽

Parallel Reaction ◽

Molybdenum Catalysts ◽

The Difference ◽

Kinetics Of ◽

Alumina Catalysts

Kinetics of isomerisation of cyclohexene to methylcyclopentene proceeding as parallel reaction to hydrogenation of cyclohexene to cyclohexane on cobalt-molybdenum catalysts of different composition has been measured. The surface acidity of these catalysts was estimated from the difference in the adsorption of toluene and heptane which was measured by chromatographic method. In a series of catalysts containing molybdenum the acidity parallels isomerisation activity. Cobalt on alumina catalysts and alumina itself have greater acidity but exhibit lower isomerisation activity compared to the catalysts containing molybdenum.

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Oxidation behavior of non-stoichiometric (Zr,Hf,Ti)Cx carbide solid solution powders in air

Journal of Advanced Ceramics ◽

10.1007/s40145-021-0469-y ◽

2021 ◽

Author(s):

Huilin Lun ◽

Yi Zeng ◽

Xiang Xiong ◽

Ziming Ye ◽

Zhongwei Zhang ◽

...

Keyword(s):

Solid Solution ◽

Oxidation Resistance ◽

Oxidation Behavior ◽

Group Iv ◽

Hypersonic Vehicles ◽

Metal Carbides ◽

Initial Oxidation ◽

Plasma Sintering ◽

Spark Plasma ◽

Kinetics Of

AbstractMulti-component solid solutions with non-stoichiometric compositions are characteristics of ultra-high temperature carbides as promising materials for hypersonic vehicles. However, for group IV transition-metal carbides, the oxidation behavior of multi-component non-stoichiometric (Zr,Hf,Ti)Cx carbide solid solution has not been clarified yet. The present work fabricated four kinds of (Zr,Hf,Ti)Cx carbide solid solution powders by free-pressureless spark plasma sintering to investigate the oxidation behavior of (Zr,Hf,Ti)Cx in air. The effects of metallic atom composition on oxidation resistance were examined. The results indicate that the oxidation kinetics of (Zr,Hf,Ti)Cx are composition dependent. A high Hf content in (Zr,Hf,Ti)Cx was beneficial to form an amorphous Zr-Hf-Ti-C-O oxycarbide layer as an oxygen barrier to enhance the initial oxidation resistance. Meanwhile, an equiatomic ratio of metallic atoms reduced the growth rate of (Zr,Hf,Ti)O2 oxide, increasing its phase stability at high temperatures, which improved the oxidation activation energy of (Zr, Hf, Ti)Cx.

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Model for Epitaxial growth of Cobalt on CU(100)

MRS Proceedings ◽

10.1557/proc-160-221 ◽

1989 ◽

Vol 160 ◽

Cited By ~ 1

Author(s):

Dimitri D. Vvedensky ◽

Shaun Clarke

Keyword(s):

Epitaxial Growth ◽

Growth Kinetics ◽

Solid Model ◽

Free Energies ◽

Diffusion Parameters ◽

The Difference ◽

Kinetics Of

AbstractThe epitaxial growth kinetics of Co on Cu(100) are investigated with a kinetic solid-on-solid model. Two effects are found to dominate the growth of this system reflecting the difference in surface free energies betweenthe two materials: the difference of diffusion parameters, and the inability of Co to wet Cu(100) at lower temperatures.

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Kinetics of mercury accumulation by freshwater biofilms

Environmental Chemistry ◽

10.1071/en17073 ◽

2017 ◽

Vol 14 (7) ◽

pp. 458 ◽

Cited By ~ 3

Author(s):

Perrine Dranguet ◽

Vera I. Slaveykova ◽

Séverine Le Faucheur

Keyword(s):

Food Webs ◽

Food Chain ◽

Microbial Composition ◽

Biofilm Thickness ◽

Aquatic Microorganisms ◽

Uptake Rate Constant ◽

The Difference ◽

Accumulation Kinetics ◽

Kinetics Of ◽

Hg Accumulation

Environmental contextMercury (Hg) is a major environmental contaminant due to its toxicity, accumulation and biomagnification along the food chain. We demonstrate that Hg accumulation by biofilms, one possible entry point for Hg into food webs, is rapid and depends on biofilm structure and composition. These findings have important implications for the understanding of Hg bioavailability and effects towards aquatic microorganisms. AbstractMercury contamination is of high concern due to its bioaccumulation, toxicity and biomagnification along the food chain. Biofilms can accumulate Hg and contribute to its incorporation in freshwater food webs. Nevertheless, the accumulation kinetics of Hg by biofilms is not well described and understood. The aim of the present study was thus to gain mechanistic understanding of Hg accumulation by biofilms. Kinetics of Hg uptake by biofilms of different ages (e.g. different compositions) was characterised by determining Hg contents in biofilms with and without a cysteine-washing step. Hg accumulation was rapid in both biofilms, with the uptake rate constant of the younger biofilm 10 times higher than that of the older biofilm. Moreover, accumulated Hg reached a plateau at 24h exposure in the younger biofilm, whereas it increased linearly in the older biofilm. The observed difference in Hg uptake by the studied biofilms is likely a result of the difference in biofilm thickness (and thus Hg diffusion inside the biofilm matrix) and microbial composition. These findings have important implications for the understanding of Hg bioavailability and effects towards aquatic microorganisms.

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