PROTONATION EQUILIBRIA OF L-DOPA AND 1,10 PHENONTHROLINE IN PROPYLENE GLYCOL-WATER MIXTURES

Journal of The Chilean Chemical Society

SANTHEE DEVI, K V¹  PADMAJA, N¹  RAMA RAJU, B¹  NAGESWARA RAO, G¹ 

[1] Andhra University, Visakhapatnam, India

关键词: Protonation equilibria;    propylene glycol;    L-;    Dopa;    1;    10-;    Phenanthroline;   

DOI  :  10.4067/S0717-97072011000400004

学科分类：化学（综合）

来源: Sociedad Chilena de Quimica

【 摘 要 】

Protonation equilibria of L-Dopa and 1,10 phenonthroline have been studied in varying concentrations (0-60% v/v) of propylene glycol-water mixtures maintaining an ionic strength of 0.16 mol dm-3 at 303 K using pH metric method. The protonation constants have been calculated with the computer program MINIQUAD75 and the best fit models are arrived at based on statistical grounds employing crystallographic R factor, χ2 , skewness and kurtosis. Dopa has three dissociable protons and one amino group which associate with proton. It exists as LH4+ at low pH and gets deprotonated with the formation of LH3, LH2- and LH2- successively with increase in pH. Phen forms LH22+ at low pH and gets deprotonated with the formation of LH+ and L with increase in pH. Secondary formation functions confirm the existence of 3 and 2 protonation equilibria for dopa and phen, respectively. The linear increase of log values of protonation constants of Dopa with decreasing dielectric constant of PG-water mixtures indicates the dominance of electrostatic forces in the protonation-deprotonation equilibria. Phen exhibits non-linear trend indicating the dominance of non-electrostatic forces.

【 授权许可】

Unknown