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

The mechanism of luminol chemiluminescence is a special case of nucleophilic addition to carbonyl compounds. The breakdown of the key intermediate, an alpha hydroxy hydroperoxide, produces a peracid ortho to an acyl diazene group. After intramolecular addition of the peracid, the energy from nitrogen expulsion is utilized in the formation of an anti-aromatic endoperoxide. Rupture along the O,O bond leaves a substantial part of the ensuing phthalate in its excited state. The emitter is shown to be a mono-protonated phthalate unaccessible by photoexcitation. The dark reaction is a concerted decomposition of the alpha hydroxy hydroperoxidixe to yield ground-state phthalate.

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The reduction of TcO 4to TcO 2 ‚nH 2 O by Fe(II) in slightly acid to basic solution has been investigated in an all-glass reaction vessel with a hydrophobic inner surface. The three-electron reduction process, although thermodynamically feasible, was found to proceed very slowly if at all. Fe(II) sorbed on the wall of untreated reaction vessels or precipitated as Fe(OH) 2 (s) or FeCO 3 (s) was found to reduce TcO 4 -, the observed rates being proportional to the amount of sorbed or precipitated Fe(II). The experimental results are discussed in light of the standard redox potentials and possible reaction paths leading from TcO 4to TcO 2 ‚nH 2 O.