A potentiometric study of acid–base equilibria of substituted pyridines in acetonitrile

Augustin-Nowacka, Danuta; Chmurzyński, Lech

doi:10.1016/s0003-2670(98)00771-5

Cited by 62 publications

(64 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Cationic standard heteroconjugation constants in systems involving substituted pyridines in DMSO are shown in table 3, together with those previously determined in other non-aqueous solvents, amphiprotic methanol, (11) and the aprotic protophobic acetone, (11) acetonitrile, (8) and nitromethane. (5) Values of lgK f of the cationic standard heteroconjugation constants (table 3) range between 1.5 and 3.20.…”

Section: Resultsmentioning

confidence: 87%

“…(8) The procedures for preparation and purification of 2,6-dinitrophenol, tetran-butylammonium 2,6-dinitrophenolate, tetra-n-butylammonium perchlorate, and tetra-nbutylammonium chloride were also described previously. (8,11) A cell for the e.m.f. measurements was assembled as follows: glass electrode | the system studied || modified calomel electrode.…”

Section: Methodsmentioning

confidence: 99%

“…The heteroconjugation reactions between protonated base BH + and free base B 1 were studied in o-dichlorobenzene, (1,2) chlorobenzene, (1,2) nitrobenzene, (3,4) nitromethane, (4,5) acetonitrile, (6)(7)(8) acetone, (9)(10)(11) propylene carbonate (12) and methanol (11) on the basis of conductometric, (1)(2)(3) solubility, (4,9) potentiometric, (6-8, 10, 11) and calorimetric (12) methods. The asymmetric hydrogen bond in (NHN) + bridges was also investigated by i.r.…”

Section: Introductionmentioning

confidence: 99%

“…It can be concluded that the tendency towards cationic heteroconjugation in systems of protonated pyridine derivatives and conjugate free bases in polar aprotic solvents like nitromethane, acetonitrile, and acetone is rather poor. (5,8,11) In most of the systems, the equilibrium is either completely absent or the equilibrium constants are so small that they cannot be measured potentiometrically. It is quite striking that, in the amphiprotic methanol, a solvent regarded as rather unfavourable for conjugation equilibria, the cationic standard heteroconjugation constants could be measured for most of the substituted pyridine systems.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Potentiometric studies of cationic heteroconjugation equilibria in systems involving free and protonated pyridine derivatives in dimethyl sulfoxide

Augustin-Nowacka

Makowski

Chmurzyński

2002

The Journal of Chemical Thermodynamics

View full text Add to dashboard Cite

Section: Resultsmentioning

confidence: 87%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Potentiometric studies of cationic heteroconjugation equilibria in systems involving free and protonated pyridine derivatives in dimethyl sulfoxide

Augustin-Nowacka

Makowski

Chmurzyński

2002

The Journal of Chemical Thermodynamics

View full text Add to dashboard Cite

“…(11) resulting to the mobilities of fully complexed BA 2 and AHBA 2 and the formation constants of BA…”

Section: Multiple Complexationmentioning

confidence: 99%

Electromigration of a heteroconjugated imidazole–acetate complex in ACN

Porras

Jussila

2007

Electrophoresis

View full text Add to dashboard Cite

ACN is an extremely poor hydrogen bond donor and therefore the anions dissolved in it are solvated mainly by other hydrogen bond donors (e.g. uncharged acids) possibly present in the solution. Under properly selected experimental conditions stabilization via hydrogen bonding can be used for separation in CE as has been demonstrated for uncharged acids by several authors. Electromigration based on heteroconjugation can be of importance, e.g. when aqueous separation medium cannot be used due to stability reasons. It also allows CE to be used as a tool for solution chemistry measurements, if the required physicochemical properties of the studied system are known or they can be predicted with sufficient accuracy by existing theories. In the present work we showed that also an uncharged base can stabilize an anion via hydrogen bonding in ACN. In the setup imidazole was chosen as a model base and acetate ion as complexing anion in equimolar acetic acid-acetate buffer. The resulted hydrogen-bonded imidazole-acetate complex (i.e. heteroconjugate) possesses a charge and can thus migrate in CE. It was shown that the studied complexation in ACN is sensitive to competition by other hydrogen bond donors such as water and methanol. On the other hand, acetone, which is a poor hydrogen bond donor, did not have much effect on the complexation. To take the effect of ionic strength on mobility into account, mobilities of the imidazole-acetate complex measured at various ionic strengths were corrected to zero ionic strength by the aid of conductivity equation. A fit of the 1:1 binding isotherm to the ionic strength corrected mobility versus acetate concentration data led to rather good correlation. However, x-reciprocal linear transformation of the binding isotherm showed nonlinearity, which could be partly explained by homoconjugation of acetic acid and acetate ion. Since the homoconjugation constant for acetic acid under present experimental conditions was not available, theoretical simulations were used to demonstrate the effects of homoconjugation. The possibility of multiple complexation of imidazole was discussed as well.

show abstract