KINETIC ISOTOPE EFFECTS FROM REACTIONS OF MUONIUM ATOMS IN WATER WITHVARIOUS KETONES, AND ACETALDEHYDE - CONTRASTS WITH HYDROGEN-ATOMS

This paper presents data showing that in dilute aqueous solutions of b utanone, 3-pentanone, cyclohexanone, di-tert-butyl ketone, and acetald ehyde the addition reaction of muonium atoms occurs with a rate consta nt close to 1 x 10(8) M-1 s(-1). The same value was obtained previousl y for acetone. Thus the reaction rate is virtually independent of the group attached to the C=O, be it a methyl, methylene, tert-butyl, or e ven a hydrogen atom. This is in sharp contrast to the reactivity of or dinary H-1 atoms, whose rate constants are much slower and dependent o n adjacent groups. In fact muonium and H-1 react by different mechanis ms, to form different products, so their rate ratio represents a compl ex kinetic isotope effect.