A study of the tendency of organic bases towards cationic heteroconjugation in polar non-aqueous solvents

Kaczmarczyk, Ewa; Augustin-Nowacka, Danuta; Makowski, Mariusz; Kozák, Anna; Chmurzyński, Lech

doi:10.1039/b100211m

Cited by 8 publications

(6 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In DMF and similar solvents the dissociation process of neutral acids is superimposed by the homoconjugation and heteroconjugation reactions [39,40,49], but in some cases these conjugation reactions may occur also in hydrogen bond donor solvents (see, e.g., [39,51] ). It is of interest that with the suitable selection of the experimental conditions, heteroconjugation can be used as a separation mechanism in CE; this has been demonstrated by Okada [52][53][54] and subsequently by others [55][56][57][58].…”

Section: Introductionmentioning

confidence: 99%

Capillary electrophoresis in N,N‐dimethylformamide

Porras

Kenndler

2005

Electrophoresis

View full text Add to dashboard Cite

N,N-Dimethylformamide (DMF) is a dipolar protophilic solvent with physicochemical properties that makes it suitable as solvent for capillary electrophoresis (CE). It is prerequisite for the proper application of CE to adjust and to change the pH of the background electrolyte (BGE) in a defined manner. This was done in the present work using benzoic acid-benzoate by selecting different concentration ratios of acid and salt, and calculating the theoretical pH from the activity-corrected Henderson-Hasselbalch equation. The mobilities of the analytes (chloro- and nitro-substituted phenolates) were found to follow reasonably well the typical sigmoid mobility versus pH curve as predicted by theory. The actual mobilities and pK(a) values (at 25 degrees C) of the analytes were derived from these curves. pK(a) values were in the range of 11.1-11.7, being thus 3-4.4 units higher than in water. This pK(a) shift is caused by the destabilization of the analyte anion and the better stability (solubility) of the molecular analyte acid in DMF, which overcome the higher basicity of DMF compared to water. Absolute mobilities were calculated from the actual mobilities; they were between 32x10(-9) and 42x10(-9) m(2)/Vxs. Slight deviations of the measured mobilities from the theoretical mobility versus pH curve were discussed on the bases of ion pairing and heteroconjugation and homoconjugation of either buffer components or buffer components and analytes. Heteroconjugation was used as a mechanism for the electrically driven separation of neutral analyte molecules in a BGE where salicylate acted as complex forming ion. Rough estimation of the complexation constants for the phenolic analytes gave values in the range of 100-200 L/mol. Addition of water to the solvent decreased the effect of heteroconjugation, but it was still present up to the surprisingly high concentration of 20% water. Electrophoretically relevant parameters like ionic mobilities and pK(a) values, and conjugation and ion pairing are dependent on the water content of the solvent. The water uptake of DMF was measured when exposed to humidity of ambient air. The resulted behavior of the water uptake was found rather similar to that for acetonitrile and methanol.

show abstract

Section: Introductionmentioning

confidence: 99%

Capillary electrophoresis in N,N‐dimethylformamide

Porras

Kenndler

2005

Electrophoresis

View full text Add to dashboard Cite

show abstract

“…Auxiliary materials: picric acid, tetra-n-butyl-ammonium picrate, 2,6-dinitrophenol, tetra-n-butyl-ammonium 2,6-dinitrophenolate and tetraethyl-ammonium chloride were purified as reported elsewhere [7].…”

Section: Methodsmentioning

confidence: 99%

Investigations of (acid+base) equilibria in systems modelling interactions occurring in biomolecules

Kozák

Czaja

Chmurzyński

2006

The Journal of Chemical Thermodynamics

Self Cite

View full text Add to dashboard Cite

“…Picric acid, tetra-n-butylammonium picrate, chloride and perchlorate were all purified as described elsewhere [8]. n-Butylamine was repeatedly distilled over KOH using Widmer column.…”

Section: Methodsmentioning

confidence: 99%