A contribution to the kinetic study of peptides chlorination, pH influence, and peptic bond unity interaction with HOCl

This work is aimed to constitute a contribution to the kinetic study of chl orine consumption by the peptides (Val-Gly), (Gly-Leu), Glutation (Glu-Cys- Gly), and their constitutive amino acids. The study of amino acids has only been carried out to understand the chlorination process of the correspondi ng peptides. As most studies were achieved using only free amino acids under extreme con ditions of pH, we have examined the pH influence on the peptides,chlorinati on reaction rate. Various peptides and amino acids were used, and the chose n pH range was close the treated water's pH (6 < pH < 10). The reactivity o f the peptic bond unity with respect to chlorine has also been studied. The obtained results have made it possible to show that the degradation rat e of chlorine can be expressed by a second-order kinetic law, order 1 per c ontribution with chlorine and order 1 per contribution with the reactive si tes. The acidity of the reactive medium has a strong influence on the react ion rate. The apparent rate constant, k, increases with pH up to pH 8, decr easing for higher pH values, which can be attributed to various facts. On the other hand,many studies concerning the interaction existing between chlorine and the peptic bond unity have been performed. The majority of tho se studies were based on calculation approach, giving contradictory results . We have carried out a series of chlorination experiments on products wher e the primary amine function is protected. Our results make possible to aff irm by a calculation approach, and by the chlorination of the protected pep tides, that the peptic bond unity does not react directly with chlorine.