Acid-Base Equilibria of Substituted Pyridine N-Oxides in N,N-Dimethylformamide and Dimethyl Sulfoxide

1993 ◽  
Vol 46 (2) ◽  
pp. 185 ◽  
Author(s):  
L Chmurzynski ◽  
Z Warnke
Keyword(s):  
Dimethyl Sulfoxide ◽  
Linear Relationship ◽  
Aprotic Solvent ◽  
Heterocyclic Amines ◽  
Aprotic Solvents ◽  
Acid Base ◽  
Acidity Constants ◽  
Pka Values ◽  
Weak Tendency

Acidity constants have been determined potentiometrically for a variety of conjugate acids of substituted pyridine N-oxides in N,N- dimethylformamide ( dmf ) and dimethyl sulfoxide ( dmso ). The pKa values in these solvents varied in the same direction and correlated with the pKa values of these species in water and in the protophobic aprotic solvent acetonitrile. Further, a linear relationship has been established between the pKa values in the two protophilic aprotic solvents under study. The most basic substituted pyridine N-oxides exhibited a weak tendency towards cationic homoconjugation in dmf , whereas in the more basic dmso the homoconjugation equilibrium was not established for any of the heterocyclic N-oxides. The phenomenon of cationic homoconjugation was also not observed with pyridine as a representative of heterocyclic amines, both in dmf and dmso. This finding complies with the results obtained in other polar aprotic solvents.

A potentiometric study of (acid+base) equilibria in substituted 4-nitropyridine N-oxide systems in methanol and dimethyl sulfoxide

2007 ◽  
Vol 39 (2) ◽  
pp. 309-315 ◽  
Author(s):  
Łukasz Gurzyński ◽  
Aniela Puszko ◽  
Mariusz Makowski ◽  
Lech Chmurzyński
Keyword(s):  
Dimethyl Sulfoxide ◽  
Acid Base ◽  
Oxide Systems ◽  
Potentiometric Study

scholarly journals The comparative study of linear solvatation energy relationship for the reactivity of pyridine carboxylic acids with diazodiphenylmethane in protic and aprotic solvents

2012 ◽  
Vol 77 (10) ◽  
pp. 1311-1338 ◽  
Author(s):  
Sasa Drmanic ◽  
Jasmina Nikolic ◽  
Aleksandar Marinkovic ◽  
Bratislav Jovanovic
Keyword(s):  
Solvent Effects ◽  
Kinetic Data ◽  
Aprotic Solvent ◽  
Isonicotinic Acid ◽  
Linear Regression Analysis ◽  
Multiple Linear Regression Analysis ◽  
Reaction Rates ◽  
Aprotic Solvents ◽  
Pyridine Carboxylic ◽  
The Comparative Study

Protic and aprotic solvent effects on the reactivity of picolinic, nicotinic and isonicotinic acid, as well as of some substituted nicotinic acids with diazodiphenylmethane (DDM) were investigated. In order to explain the kinetic results through solvent effects, the second-order rate constants for the reaction of the examined acids with DDM were correlated using the Kamlet-Taft solvatochromic equation. The correlations of the kinetic data were carried out by means of the multiple linear regression analysis and the solvent effects on the reaction rates were analyzed in terms of the contributions of the initial and the transition state. The signs of the equation coefficients support the already known reaction mechanism. The solvatation models for all the investigated acids are suggested and related to their specific structure.

Electron-transfer reactions in non-aqueous media. VII. Reduction of CoF(NH3)52+ and Co(HCOO)(NH3)52+ by copper(I) in dimethyl sulfoxide-water mixtures

1983 ◽  
Vol 36 (10) ◽  
pp. 1923 ◽  
Author(s):  
JMB Harrowfield ◽  
L Spiccia ◽  
DW Watts
Keyword(s):  
Electron Transfer ◽  
Dimethyl Sulfoxide ◽  
Aqueous Media ◽  
Mixed Solvents ◽  
Transfer Reactions ◽  
Aprotic Solvents ◽  
Aqueous Mixtures ◽  
Electron Transfer Reactions ◽  
Dipolar Aprotic Solvents ◽  
Sphere Mechanism

Previous work on the reduction of a series of cobalt(III) complexes by iron(II) in dipolar aprotic solvents and in aqueous mixtures has been extended to reduction by copper(I). The greater stability of copper(I) to disproportionation in these media has permitted the study of the reduction of CoF(NH3)52+ and Co(HCOO)(NH3)52+ in range of solvents over a number of temperatures with a precision not possible in previous studies in water. The results are consistent with an inner-sphere mechanism in which the copper(I) reductant is preferentially solvated by dimethyl sulfoxide to the exclusion of water in mixed solvents.

Surface Chemistry of Mesoporous Materials: Effect of Nanopore Confinement

2002 ◽  
Vol 751 ◽  
Author(s):  
Yifeng Wang ◽  
Charles Bryan ◽  
Huifang Xu ◽  
Huizhen Gao
Keyword(s):  
Surface Chemistry ◽  
Surface Acidity ◽  
Scale Space ◽  
Acid Base ◽  
Acidity Constants ◽  
Solution Interface ◽  
Ion Sorption ◽  
Alumina Particles ◽  
The Difference ◽  
Nanopore Confinement

AbstractAcid-base titration and metal sorption experiments were performed on both mesoporous alumina and alumina particles under various ionic strengths. It has been demonstrated that surface chemistry and ion sorption within nanopores can be significantly modified by a nano-scale space confinement. As the pore size is reduced to a few nanometers, the difference between surface acidity constants (ΔpK = pK2 – pK1) decreases, giving rise to a higher surface charge density on a nanopore surface than that on an unconfined solid-solution interface. The change in surface acidity constants results in a shift of ion sorption edges and enhances ion sorption on that nanopore surfaces.

Influence of plasma bicarbonate concentration and pH on citrate excretion

1964 ◽  
Vol 206 (4) ◽  
pp. 875-882 ◽  
Author(s):  
David P. Simpson
Keyword(s):  
Linear Relationship ◽  
Metabolic Alkalosis ◽  
High Plasma ◽  
Alkaline Ph ◽  
Acid Base Balance ◽  
Bicarbonate Concentration ◽  
Acid Base ◽  
Plasma Bicarbonate ◽  
Close Relationship ◽  
Base Balance

Citrate excretion has been studied in dogs under various conditions of acid-base balance in order to determine which factors are responsible for the increased citrate clearance present in metabolic alkalosis. A close relationship, significantly modified by systemic pH, was found between plasma bicarbonate concentration and citrate clearance. In the presence of an alkaline plasma pH, there was a linear relationship between changes in plasma bicarbonate concentration and changes in citrate clearance. Other experiments also demonstrated the influence of plasma bicarbonate concentration on citrate clearance at alkaline pH. Under acidotic conditions citrate clearances were low and changes in plasma bicarbonate concentration had little effect on citrate excretion. A change in plasma pH from an acidotic to an alkalotic state, with a constant plasma bicarbonate concentration, produced an increase in citrate clearance. Thus the coexistence in metabolic alkalosis of high plasma bicarbonate concentration and high plasma pH results in a markedly increased citrate clearance.

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