Volume of Association of Charge-Transfer Interaction of 1-Methyl-3-(carbomethoxy)pyridinium Iodide and Sodium 8-Chlorotheophyllinate in Aqueous Solution

Article abstract of DOI:10.1021/j150645a022

Values have been obtained for the association constant for the interaction of sodium 8-chlorotheophyllinate with 1-methyl-3-(carbomethoxy)pyridinium iodide in aqueous solution at pH 7.0, I = 0.20, at various temperatures and pressures.From these data the apparent volume change on association is estimated to be Δ<*> = -6.5 (+/-0.5) cm³mol^-1 at 25 deg C.Values for the compressibility increment were obtained within the range of Δ_K = (1.6-2.0) x 1E-9 Pa^-1.Values were also obtained for the association constant of sodium 8-chlorotheophyllinate with the methyl ester of trans-cinnamic acid in a methanol and water mixture at 1-atm pressure.The results are interpreted in terms of the volume change to be expected on association due to ion pairing, and the approach of aromatic rings in water.