The kinetics and products of the chlorination of caffeine in aqueous solution

Abstract

The kinetics and products of the reaction between aqueous hypochlorous acid and caffeine have been evaluated. The reaction was found to be dependent on pH only to the extent that it influences the fraction of FAC which is in the form of HOCl. The kinetics were found to be well represented by the expression: d[Caff.] dt = −k [Caff.][HOCl] 2 The rate constant had a value of 162 ± 32 M −2 s −1. For each mol of caffeine consumed, 6.3 mol of FAC were consumed. The chlorination reaction proceeded primarily by ring cleavage and rearrangement forming nonoaromatic nitrogen heterocycles. 8-Chlorocaffeine was unequivocally identified as an aqueous chlorination product but was found to be formed only to a small extent and under rather limited conditions. No stable organic chloramines were formed.