C−H Bond Activation in Aqueous Solution:  A Linear Free Energy Relationship Investigation of the Rate-Limiting Step in the H/D Exchange of Alcohols Catalyzed by a Molybdocene

2001 ◽  
Vol 20 (18) ◽  
pp. 3864-3868 ◽  
Author(s):  
Kerry L. Breno ◽  
David R. Tyler
Keyword(s):  
Aqueous Solution ◽  
Free Energy ◽  
Bond Activation ◽  
Linear Free Energy Relationship ◽  
Linear Free Energy ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

Vanadium(V) oxyanions. The dependence of vanadate alkyl ester formation on the pKa of the parent alcohols

1988 ◽  
Vol 66 (9) ◽  
pp. 2294-2298 ◽  
Author(s):  
Alan S. Tracey ◽  
Bruno Galeffi ◽  
Soroush Mahjour
Keyword(s):  
Aqueous Solution ◽  
Nuclear Magnetic Resonance ◽  
Free Energy ◽  
Resonance Spectroscopy ◽  
Linear Free Energy Relationship ◽  
Alkyl Esters ◽  
Linear Free Energy ◽  
Ester Formation ◽  
Interesting Correlation ◽  
Extra Electron

The interaction of vanadate (VO4H21−) with a variety of alkyl alcohol's (ROH) covering about seven pKa units of acidity have been studied in aqueous solution by 51V nuclear magnetic resonance spectroscopy. A linear free energy relationship between the equilibrium constant for the formation of the vanadate monoester (HOVO3R1−) and the acidity of the alcohol was established at 23 °C. The correlation was found to be [Formula: see text] where K = [HOVO3R1−]/[VO4H21−][ROH]. This correlation was shown not to extend to ligands with π-bonding capability such as phenols or phosphates, where the products are highly favoured relative to the alkyl esters. An interesting correlation between pKa values of the product esters and the pKa of the parent alcohols was also observed. It was found that below a [Formula: see text] of about 15 the pKa values of the esters were essentially constant. However, above this value of 15 the pKa of the ester was found to increase rapidly with an increase in pKa of the alcohol. This result may indicate that the electron accepting ability of the metal is exhausted with the higher pKa alcohols, and the extra electron density is transferred to the oxygens, thus causing an increase in pKa of the ester.

THEORETICAL STUDY ON CUI-CATALYZED LIGAND-FREE N-ARYLATION OF IMIDAZOLE WITH BROMOBENZENE

2012 ◽  
Vol 11 (05) ◽  
pp. 1135-1147 ◽  
Author(s):  
HAN GUO ◽  
YING XUE
Keyword(s):  
Free Energy ◽  
Energy Barrier ◽  
Density Functional ◽  
Oxidative Addition ◽  
Reductive Elimination ◽  
Free Energy Barrier ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Ligand Free ◽  
Rate Limiting

The density functional theory (DFT) is used to investigate the mechanism of ligand-free CuI -catalyzed N -arylation of imidazole with aryl halide. The oxidative addition/reductive elimination mechanism is adopted via two different pathways to form the same Cu(III) intermediate. Comparing two pathways, the path 1 in which the imidazolyl coordination occurs prior to the oxidative addition is more favorable, because the free energy barrier of the rate-limiting step of path 1 is lower than the barrier of the other. In addition, it leads to a relative stable intermediate which can promote the reaction to process via path 1. And the overall free energy barrier of oxidative addition to imidazole-ligated Cu(I) complex is not high enough when comparing with the diamine-promote process, which can further prove that the N -arylation of imidazole is feasible in the absence of additional ligands. Nucleophile coordination and reductive elimination steps are facile, while the oxidative addition is the rate-limiting step.

Kinetics of Pb(IV) Oxidation of Substituted Methyl Mandelates — A L.F. E. R. Study

1986 ◽  
Vol 41 (4) ◽  
pp. 467-472
Author(s):  
Sudheer K. Banerjee ◽  
R. Shanker ◽  
Om P. Sachdeva
Keyword(s):  
Bond Rupture ◽  
Linear Free Energy Relationship ◽  
First Order ◽  
Keto Esters ◽  
Linear Free Energy ◽  
Kinetic Isotope ◽  
Rate Limiting Step ◽  
Catalysed Reaction ◽  
Reaction Constant ◽  
Rate Limiting

Lead tetra acetate (Pb(IV) or LTA) oxidation of the esters X -C6H4-CH(OH)-COOCH3(X = H, m-NO2, p-NO2, m-Cl, p-Cl, p-Br. p-CH3 and p-C2H5) gives corresponding keto esters. The reaction is first order in [Pb(IV)] and second order in [Ester], and is catalysed by pyridine and 2,6-lutidine. The pyridine catalysed reaction is first order each in [Pb(IV)]. [Ester] and [Pyridine]. A kinetic isotope effect is observed in oxidation of methyl m andelate for both uncatalysed reaction (kH/kD = 4.2) and pyridine catalysed reaction (kH/kD = 1.8). Activation param eters for both uncatalysed and pyridine catalysed reactions are evaluated. The results are in accord with Linear Free Energy Relationship (L.F.E.R.) and the reaction constant (ϱ = +0.75) obtained supports proton transfer in the ɑ-C-H bond rupture in the rate limiting step. The role pf pyridine in catalysis, as a ligand or as a base is discussed

scholarly journals Prediction of Adsorbability of Organic Compounds from Aqueous Solution on Activated Carbon by Means of the Linear Free-energy Relationship

1983 ◽  
Vol 56 (4) ◽  
pp. 1002-1005 ◽  
Author(s):  
Ikuo Abe ◽  
Katsumi Hayashi ◽  
Mutsuo Kitagawa ◽  
Tsuneaki Hirashima
Keyword(s):  
Aqueous Solution ◽  
Free Energy ◽  
Activated Carbon ◽  
Organic Compounds ◽  
Linear Free Energy Relationship ◽  
Linear Free Energy

THEORETICAL INVESTIGATION ON THE ACTIVATION OF ETHANE VIA NICKEL ATOM CATALYSIS

2007 ◽  
Vol 06 (02) ◽  
pp. 323-330 ◽  
Author(s):  
LAI-CAI LI ◽  
JUN-LING LIU ◽  
JING SHANG ◽  
XIN WANG ◽  
NING-BEW WONG
Keyword(s):  
Density Functional ◽  
Bond Activation ◽  
Theoretical Work ◽  
Nickel Atom ◽  
Functional Theory ◽  
Activation Pathway ◽  
Rate Determining Step ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

The reaction mechanism of the activation of ethane by nickel atom has been investigated by density functional theory (DFT). The geometries and vibration frequencies of reactants, intermediates, transition states and products have been calculated at the B3LYP/6-311 + +G(d, p) level. Two main pathways, C – C bond activation and C – H bond activation, are identified. In former channel, the rate-limiting step is found to be hydrogen-transferring step with a high barrier of 227 kJ · mol-1. In the C – H bond activation pathway, the second hydrogen-transferring step is the rate-determining step of the whole reaction. The barrier of the step is 71 kJ · mol-1. Our results show that the studied reaction would undergo along C – H bond activation pathway to form the products H 2 molecule and Ni ⋯ethene complex. The present theoretical work indicates that Ni atom is more active than Ni + cation in activating ethane.

Rate-Limiting Step of the Rh-Catalyzed Carboacylation of Alkenes: C–C Bond Activation or Migratory Insertion?

2011 ◽  
Vol 134 (1) ◽  
pp. 715-722 ◽  
Author(s):  
J. Patrick Lutz ◽  
Colin M. Rathbun ◽  
Susan M. Stevenson ◽  
Breanna M. Powell ◽  
Timothy S. Boman ◽  
...  
Keyword(s):  
Bond Activation ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Migratory Insertion ◽  
Rate Limiting

Ornithine Decarboxylase Activity in Cultured Endothelial Cells Stimulated by Serum, Thrombin and Serotonin

1978 ◽  
Vol 39 (02) ◽  
pp. 496-503 ◽  
Author(s):  
P A D’Amore ◽  
H B Hechtman ◽  
D Shepro
Keyword(s):  
Endothelial Cells ◽  
Ornithine Decarboxylase ◽  
Decarboxylase Activity ◽  
Aortic Endothelial Cells ◽  
Ornithine Decarboxylase Activity ◽  
Rate Limiting Step ◽  
Bovine Aortic Endothelial Cells ◽  
Limiting Step ◽  
Rate Limiting ◽  
Serum Serotonin

SummaryOrnithine decarboxylase (ODC) activity, the rate-limiting step in the synthesis of polyamines, can be demonstrated in cultured, bovine, aortic endothelial cells (EC). Serum, serotonin and thrombin produce a rise in ODC activity. The serotonin-induced ODC activity is significantly blocked by imipramine (10-5 M) or Lilly 11 0140 (10-6M). Preincubation of EC with these blockers together almost completely depresses the 5-HT-stimulated ODC activity. These observations suggest a manner by which platelets may maintain EC structural and metabolic soundness.

Dynamics of hepatic and peripheral insulin effects suggest common rate-limiting step in vivo

Diabetes ◽  
1993 ◽  
Vol 42 (2) ◽  
pp. 296-306 ◽  
Author(s):  
D. C. Bradley ◽  
R. A. Poulin ◽  
R. N. Bergman
Keyword(s):  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting
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