solvent molecules. Each of these considerations regarding transition-state formation would contribute to the solvent dependence exhibited by the kinetic activation parameters listed in Table II.Both mass effects and relative hydrogen-bonding versus deuterium-bonding energies (and structure)28 are likely contributors to the different rates of racemization observed for Eu(dpa)33-in H20 versus D20 solutions. ConclusionThis is the first report of time-resolved circularly polarized luminescence (TR-CPL) from a racemic mixture of enantiomeric species excited with circularly polarized light. It is also the first report of kinetic parameters for optical isomerization of a chiral

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By pulse or gamma radiolysis in the presence of Br-, 1 -methylindole (1 b) is oxidized to its radical cation (2b), which adds to (lb) to form a radical dimer (8b). Species (2b) also reacts with OHto yield the pseudo-base, proposed to be the C,-OH adduct (4b). Identical end-product yields and spectral comparison reveal that the addition of OH' radicals to (lb) also produces (2b) and ( 4b) but virtually no other OH' adducts to (lb). The selectivity of OH towards the C, position appears to apply to the other indoles as well. The neutral indolyl radicals (3) disappear both by coupling and dismutation. Discrimination between these modes is governed by the substituent. A methyl group at the C, position favours C,-C,' coupling. Molecular oxygen adds to neutral indolyl radicals at the C, position. The measured and estimated rates of 0, addition relate to the redox potentials of the indolyl radicals. The reaction between 0,-* and the indolyl radical cation (2) produces (1) and 0,. On the other hand, 02-* couples to (3) to yield C,-OOH hydroperoxides (14). The latter decompose into C,-C3 opened amides (1 3) with concomitant chemiluminescence. Early photophysical and pulse radiolysis studies '-' aimed at Paper 9/03860D

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The rates of attack of ·OH, N· 3, Br·‐ 2, CO·‐ 3, and ClO· 2 on indole (Ia) and the methylindoles (Ib)‐(Ie) are determined.