Multiple transition state coupling

Many amorphous homopolymers and random copolymers show thermorheologically simple behavior within the usual experimental accuracy. Plazek (23,24), however, found that the steady-state viscosity and steady-state compliance of polystyrene cannot be described by the same WLF equation. The effect of temperature on entanglement couplings can also result in thermorheologically complex behavior. This has been shown on certain polymethacrylate polymers and their solutions (22, 23, 26, 31). The time-temperature superposition of thermorheologically simple materials is clearly not applicable to polymers with multiple transitions. The classical study in this area is that by Ferry and co-workers (5, 8) on polymethacrylates with relatively long side chains. In these the complex compliance is the sum of two contributions with different sets of relaxation mechanisms the compliance of the chain backbone and that of the side chains, respectively. 

Trigonal e-type modes (derived, for example, from the t2g or eg octahedral modes) can effect the following "inter-state" couplings of trigonal electronic components (Ea + Eh) e, (Ea + Ai) e, and (A2 + Eh) e. This has the consequence that vibronic components of the Ai(Aig) - Ai(T2g) transition can exhibit a nonvanishing CD which has been "borrowed" from the Ai (Aig)- -Ea(Tig) transition. Furthermore, vibronic components of the Ai(Aig) - Eh (T2g) transition may exhibit CD "borrowed" from both the A - Ea and Ai A2 trigonal components of the Aig - Tig transition. Heretofore, the appearance of multiple components in the Aig - ... 

Experience with model calculations for equilibrium isotope effects and kinetic isotope effects, when using conventional TST, shows that the RGM is valid in the common circumstance in which the effects of coupled vibrational motions cancel between reactant and product states, or between reactant and transition states. The natural coupling expected between the various bends and stretches of the bonds in a methyl group is largely the same in the reactant state and transition state in the acetyl transfer example, so the free-energy effects of multiple isotopic substitutions are strictly additive. In the case of the glutamate dehydrogenase reaction of Fig. 

Equation 3.1 through Equation 3.3 demonstrate the effects of metals that possess multiple oxidation states (transition metals) on the formation of these radicals. In Fenton-type reactions (Equation 3.1), metal oxidation is coupled to H2O2... 

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