The partition function ΣA = 1 + β1[H] + β2[H]2 + ... + βi[H]i + ... + βt[H]t was used to interpret the variation in the stepwise formation consts. for the equil. between base A and proton H. The cumulative protonation const. of the satd. complex HtA, βt = [HtA]/([H]t[A]), is equal to the ratio between the formation partition function ΣA and the dissocn. partition function ΣAD, the former giving the probability of finding compds. HiA of the ligand H binding to A and the latter giving the probability of finding species AiA by dissocn. of protons from HtA. The satn. function βt = ΣA/ΣAD can be factorized as a product of stepwise consts. βt = K1.K2...Ki...Kt. Comparisons between K1 and the geometric means βi1/i enable a calcn. to be made of the av. cooperativity consts. Kγ(i) which are explicit functions of i. The cooperativity functions γ(i) require that the equil. are described by means of model partition functions depending on the site affinity const. k and the coeffs. of the cooperativity function γ(i) = exp{2.302[a + b(i-1)]}. By analyzing the cumulative protonation consts. of polysite receptors, it is possible to det. if there actually are sep. classes of sites each with site const. kj and class cooperativity function γ(ij). The anal. of the equil. consts. of some polyprotic acids shows how both the site affinity consts. k and the slope b of log γ(i) depend on the charge d. of the base. The importance of the electrostatic effect in the binding of the proton to the base is clearly apparent. The anal. of the contribution of enthalpy to the cooperativity effect for the same compds. shows varying behavior.

Cooperativity functions and site binding constants in polyprotic acids / A., Braibanti; F., Dallavalle; Fisicaro, Emilia. - In: THERMOCHIMICA ACTA. - ISSN 0040-6031. - 140:(1989), pp. 203-217. [10.1016/0040-6031(89)]

Cooperativity functions and site binding constants in polyprotic acids

FISICARO, Emilia
1989-01-01

Abstract

The partition function ΣA = 1 + β1[H] + β2[H]2 + ... + βi[H]i + ... + βt[H]t was used to interpret the variation in the stepwise formation consts. for the equil. between base A and proton H. The cumulative protonation const. of the satd. complex HtA, βt = [HtA]/([H]t[A]), is equal to the ratio between the formation partition function ΣA and the dissocn. partition function ΣAD, the former giving the probability of finding compds. HiA of the ligand H binding to A and the latter giving the probability of finding species AiA by dissocn. of protons from HtA. The satn. function βt = ΣA/ΣAD can be factorized as a product of stepwise consts. βt = K1.K2...Ki...Kt. Comparisons between K1 and the geometric means βi1/i enable a calcn. to be made of the av. cooperativity consts. Kγ(i) which are explicit functions of i. The cooperativity functions γ(i) require that the equil. are described by means of model partition functions depending on the site affinity const. k and the coeffs. of the cooperativity function γ(i) = exp{2.302[a + b(i-1)]}. By analyzing the cumulative protonation consts. of polysite receptors, it is possible to det. if there actually are sep. classes of sites each with site const. kj and class cooperativity function γ(ij). The anal. of the equil. consts. of some polyprotic acids shows how both the site affinity consts. k and the slope b of log γ(i) depend on the charge d. of the base. The importance of the electrostatic effect in the binding of the proton to the base is clearly apparent. The anal. of the contribution of enthalpy to the cooperativity effect for the same compds. shows varying behavior.
1989
Cooperativity functions and site binding constants in polyprotic acids / A., Braibanti; F., Dallavalle; Fisicaro, Emilia. - In: THERMOCHIMICA ACTA. - ISSN 0040-6031. - 140:(1989), pp. 203-217. [10.1016/0040-6031(89)]
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11381/2426999
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 6
  • ???jsp.display-item.citation.isi??? 10
social impact