Racemization kinetics of meluadrine tartrate in aqueous solution

The kinetics of racemization of meluadrine tartrate in aqueous solution was investigated by HPLC, over the pH range of 1.2 to 12 at 40, 60 and 80 degr eesC, The racemization was followed by measuring both the residual (R)-enan tiomer and formed (S)-enantiomer of meluadrine, The pH-racemization rate profile of meluadrine showed a minimum racemizatio n rate constant between pH 4 and 6, and the rate constant increased rapidly with decreasing pH below pH 3, In the basic region, the racemization rate constant showed a maximum at around pH 9, Four pathways of racemization of meluadrine are proposed, depending on the dissociation state of the phenolic and amino groups. The calculated racemiz ation rate-pH profile agreed well with the observations. The values of acti vation energy (95-115 kJ/mol) suggest that a similar quinoid intermediate i s involved throughout the pH range examined. The objective of this study is to clarify the racemization mechanism of ben zylalcohol derivative with phenoric group. This study offers fundamental knowledge for the other benzylalcohol derivat ives, which have similar moiety structure.