Cis-trans isomerization of alkyl-substituted allylic ion pairs. 1. Isomerization of (neopentylallyl)lithium, -sodium, and -potassium in tetrahydrofuran

1986 ◽  
Vol 5 (8) ◽  
pp. 1529-1532 ◽  
Author(s):  
R. T. McDonald ◽  
S. Bywater
Keyword(s):  
Ion Pairs ◽  
Trans Isomerization ◽  
Sodium And Potassium

Ion pairs formed by alkali metals. Part 1.—Complexes of lithium, sodium and potassium with 4-nitropyridine

1975 ◽  
Vol 71 (0) ◽  
pp. 1829-1838 ◽  
Author(s):  
Pietro Cremaschi ◽  
Aldo Gamba ◽  
Gabriele Morosi ◽  
Cesare Oliva ◽  
Massimo Simonetta
Keyword(s):  
Alkali Metals ◽  
Ion Pairs ◽  
Sodium And Potassium

scholarly journals The Unanticipated Catalytic Activity of Lithium tert-Butoxide/THF in the Interesterification of Rapeseed Oil with Methyl Acetate

2019 ◽  
Vol 2019 ◽  
pp. 1-6 ◽  
Author(s):  
Valdis Kampars ◽  
Zane Abelniece ◽  
Sabine Blaua
Keyword(s):  
Catalytic Activity ◽  
Rapeseed Oil ◽  
Methyl Acetate ◽  
Methyl Esters ◽  
Ion Pairs ◽  
Molar Ratio ◽  
Fast Reaction ◽  
Branched Chain ◽  
Association Of Ions ◽  
Sodium And Potassium

Conventionally, the biodiesel (mixture of fatty acid methyl esters, FAME) production proceeds by transesterification of triglycerides with methanol accordingly by the formation of glycerol as a by-product, which cannot be included in biofuel composition. Biodiesel could also be produced via interesterification ensuring full conversion of oil to biofuel, consisting of FAME and triacetin. The most effective catalysts for interesterification reactions are alkali metal alkoxides. The effectivity of alkoxide catalyst depends on its solubility determined by the structure of the alkyl chain. In our previous studies, we have shown that the branched chain catalyst tert-BuOK/THF is highly suitable for the realisation of interesterification reactions. Till now, in the scientific literature, very little is known about the influence of metal ions. In order to investigate the influence of counterion on the activity of alkoxide catalysts, in this work, we have investigated the proceeding of interesterification reactions of rapeseed oil with methyl acetate in the presence of lithium, sodium, and potassium tert-butoxides in THF. Experimentally obtained relationships for catalyst-to-oil molar ratio (COMR) influence rapeseed oil interesterifications with methyl acetate at 55°C for 1 h, with methyl acetate-to-oil molar ratio (MAOMR) 18 showing that the tert-BuONa/THF and tert-BuOK/THF have high and similar activity, but the tert-BuOLi/THF is fundamentally different. The low and diverse activity of lithium tert-butoxide can be explained by the association of ions and very low catalytic activity of ion pairs. Simulation of the influence of association on the FAME formation shows that at COMR 0.1 (sufficient for fast reaction proceeding in the presence of tert-BuONa/THF and tert-BuOK/THF), the concentration of tert-butoxide ions in the presence of tert-BuOLi/THF because of associations lowers from 28 mmol/L to 13 mmol/L, whcih is not sufficient for effective proceeding of reaction. Activity of alkoxides in this reaction is solely determined by the counterion.

ELECTRON SPIN RESONANCE STUDIES OF RADICAL ANIONS AND ION PAIRS IN THE PYRAZINE SERIES

1965 ◽  
Vol 43 (1) ◽  
pp. 224-231 ◽  
Author(s):  
C. A. McDowell ◽  
K. F. G. Paulus
Keyword(s):  
Hyperfine Splitting ◽  
Reasonable Agreement ◽  
Ion Pairs ◽  
Steric Effects ◽  
Molecular Orbital Calculations ◽  
Radical Anions ◽  
Electronic Excitations ◽  
Spin Resonance ◽  
Sodium And Potassium ◽  
Spin Densities

The alkali metal hyperfine interaction in ion pairs of sodium and potassium cations with the radical anions of some methyl-substituted pyrazines and pyridines has been investigated. The electrostatic, electronic, and steric interactions which influence the metal hyperfine splitting are discussed in detail. It is proposed that the variation of the observed hyperfine splitting is due, in some cases, to steric effects, but in the series of m-xylene, 3,5-dimethylpyridine, and 2,6-dimethylpyrazine, the variation is caused by a change in the energy of electronic excitations from the anion to the cation.The results of molecular orbital calculations of the spin densities in tetramethylpyrazine and 3,5-dimethylpyridine are compared with experiment and found to give reasonable agreement.

Pulse Radiolytic Formation of Solvated Electrons, Ion-pairs, and Alkali Metal Anions in Tetrahydrofuran

1974 ◽  
Vol 52 (18) ◽  
pp. 3259-3268 ◽  
Author(s):  
G. A. Salmon ◽  
W. A. Seddon ◽  
J. W. Fletcher
Keyword(s):  
Alkali Metal ◽  
Alkali Metals ◽  
Dissociation Constants ◽  
Alkali Metal Cation ◽  
Ion Pairs ◽  
Alkali Metal Cations ◽  
Solvated Electrons ◽  
Sodium Potassium ◽  
Sodium And Potassium ◽  
Metal Anions

Pulse radiolysis of solutions of alkali metal cations in tetrahydrofuran (THF) demonstrates the formation of solvated electrons es−, alkali metal cation-ion pairs (M+, es−), and alkali metal anions M−. This paper describes the spectra, extinction coefficients, and radiolytic yields of es−, lithium, sodium, potassium, and cesium species in THF. The reaction kinetics are complex but largely involve reactions A and B[Formula: see text]with the concomitant disappearance of all three species by reaction with radiolytically produced radicals. Rate constants and ion-pair dissociation constants for es− and the sodium and potassium species are presented and compared with data established from studies of blue solutions of alkali metals dissolved in THF.

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