Effect of solvent on the kinetics of electroreduction of organic molecules in nonaqueous media

1983 ◽  
Vol 87 (15) ◽  
pp. 2972-2976 ◽  
Author(s):  
W. R. Fawcett ◽  
J. S. Jaworski
Keyword(s):  
Organic Molecules ◽  
Nonaqueous Media ◽  
Effect Of Solvent ◽  
Kinetics Of

Influence of medium on alkaline hydrolysis of succinic acid monomethyl and monopropyl esters

1980 ◽  
Vol 45 (11) ◽  
pp. 2873-2882
Author(s):  
Vladislav Holba ◽  
Ján Benko
Keyword(s):  
Succinic Acid ◽  
Kinetic Parameters ◽  
Alkaline Hydrolysis ◽  
Specific Interactions ◽  
Nonaqueous Media ◽  
The Media ◽  
Kinetics Of ◽  
Hydrolysis Of

The kinetics of alkaline hydrolysis of succinic acid monomethyl and monopropyl esters were studied in mixed aqueous-nonaqueous media at various temperatures and ionic strengths. The results of measurements are discussed in terms of electrostatic and specific interactions between the reactants and other components of the reaction mixture. The kinetic parameters in the media under study are related to the influence of the cosolvent on the solvation sphere of the reactants.

The Effect of Solvent on the Acid-Base Kinetics of the Excited State of β-Naphthol1

1965 ◽  
Vol 69 (6) ◽  
pp. 2044-2059 ◽  
Author(s):  
Norman M. Trieff ◽  
Benson R. Sundheim
Keyword(s):  
Excited State ◽  
Acid Base ◽  
Effect Of Solvent ◽  
Kinetics Of

scholarly journals Polar molecules catalyze CO insertion into metal-alkyl bonds through the displacement of an agostic C-H bond

2019 ◽  
Vol 116 (9) ◽  
pp. 3419-3424
Author(s):  
Tian Zhou ◽  
Santanu Malakar ◽  
Steven L. Webb ◽  
Karsten Krogh-Jespersen ◽  
Alan S. Goldman
Keyword(s):  
Transition Metal Complexes ◽  
Density Functional ◽  
Organic Molecules ◽  
Polar Molecules ◽  
Functional Theory ◽  
Bond Forming ◽  
Co Insertion ◽  
The Subject ◽  
Kinetics Of

The insertion of CO into metal-alkyl bonds is the key C-C bond-forming step in many of the most important organic reactions catalyzed by transition metal complexes. Polar organic molecules (e.g., tetrahydrofuran) have long been known to promote CO insertion reactions, but the mechanism of their action has been the subject of unresolved speculation for over five decades. Comprehensive computational studies [density functional theory (DFT)] on the prototypical system Mn(CO)5(arylmethyl) reveal that the polar molecules do not promote the actual alkyl migration step. Instead, CO insertion (i.e. alkyl migration) occurs rapidly and reversibly to give an acyl complex with a sigma-bound (agostic) C-H bond that is not easily displaced by typical ligands (e.g. phosphines or CO). The agostic C-H bond is displaced much more readily, however, by the polar promoter molecules, even though such species bind only weakly to the metal center and are themselves then easily displaced; the facile kinetics of this process are attributable to a hydrogen bonding-like interaction between the agostic C-H bond and the polar promoter. The role of the promoter is to thereby catalyze isomerization of the agostic product of CO insertion to give an η2-C,O-bound acyl product that is more easily trapped than the agostic species. This ability of such promoters to displace a strongly sigma-bound C-H bond and to subsequently undergo facile displacement themselves is without reported precedent, and could have implications for catalytic reactions beyond carbonylation.

Influence of water molecule bridges on sequestration of phenol in soil organic matter of sapric histosol

2019 ◽  
Vol 16 (7) ◽  
pp. 541 ◽  
Author(s):  
Pavel Ondruch ◽  
Jiri Kucerik ◽  
Daniel Tunega ◽  
Nadeesha J. Silva ◽  
Adelia J. A. Aquino ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Water Molecule ◽  
Organic Molecules ◽  
Desorption Kinetics ◽  
Modulated Differential Scanning Calorimetry ◽  
Time Constants ◽  
Oh Groups ◽  
Solvation Energies ◽  
Kinetics Of

Environmental contextImmobilisation of organic chemicals in soil organic matter can strongly influence their availability in the environment. We show that the presence of water clusters, called water molecule bridges, hampers the release of organic molecules from soil organic matter. Moreover, water molecule bridges are sensitive to changes in environmental conditions (e.g., temperature or moisture) which affect the release of organic molecules into the environment. AbstractWater molecule bridges (WaMB) can stabilise the supramolecular structure of soil organic matter (SOM) by connecting individual SOM molecular units. WaMB are hypothesised to act as a desorption barrier and thus to physically immobilise molecules in SOM. To test this hypothesis, we prepared two sets of soil samples – aged samples with WaMB developed, and vacuumed samples, in which WaMB were disrupted. The samples were spiked with phenol and then stored under controlled humidity. The degree of phenol immobilisation in SOM was assessed by desorption kinetics of phenol into a gas phase. This was compared with the thermal stability (T*) of WaMB obtained by modulated differential scanning calorimetry (MDSC) and the results were related to computer modelling, which provided the stability and solvation energies of phenol-WaMB-SOM models. The desorption kinetics of phenol was best described by a first-order model with two time constants ranging between 1 and 10h. In aged samples, the time constants correlated with T*, which showed that the desorption time increased with increasing WaMB stability. Molecular modelling proposed that phenol molecules are preferentially locked in nanovoids with polar OH groups pointed to WaMB in the most stable configurations. Both findings support the hypothesis that WaMB can act as a desorption barrier for phenol.

Sign in / Sign up

Export Citation Format

Share Document