The reactions of 9-substituted anthracene cation radicals (XA +.s) with water and methanol in acetonitrile were analyzed using an electron transfer stopped-flow (ETSF) method. By adopting the tris(2,4-dibromophenyl)amine cation radical (TDBPA+.) as a reaction initiator, five XA+.s, i.e. phenyl, bromo, acetyl, benzyl, and methyl derivatives, could be generated quantitatively by mixing XA with TDBPA+., and the chemical reaction processes of XA+.s with water or methanol (ROH) could then be followed by observing dynamic transformation processes of the absorption spectra. Consequently, the reaction orders of XA+. and ROH as well as the reaction rates could be determined. The order of the reactivity was anthracene+. &gt
9-methylanthracene+. &gt
9-benzylanthracene+. &gt
9-acetylanthracene+., 9-bromoanthracene+. &gt
9-phenylanthracene+., and diverse changes in the reaction orders of both XA+. and ROH were observed indicating some mechanistic changes. The order of the reactivity was difficult to explain only on the basis of the character of XAs or XA+.s. However, as a hypothesis, it can be assumed that when the electron transfer between XA+. and XA(ROH) +. is favorable to formation of XA(ROH)2+, the reaction order of [XA+.] is second, and the reaction rates become faster. © 2003 Elsevier B.V. All rights reserved.