Proposed mechanism with

If the monomer is denoted by (M) and photoexcited chelate by (C), the proposed mechanism with ethyl acetate (15,16) involves formation of an exciplex (CM ), which may revert to (C + M) or decompose to facacCM radicals and Mn(facac)2. 

A careful investigation of the reaction kinetics and detailed trapping experiments allow the conclusion that in this case a a-bond metathesis reaction mechanism applies. The polymerization reaction of PhSiH3 by CpCp Hf(SiH2Ph)Cl has been monitored by H-NMR spectroscopy. The data k(75 °C) = 1.1(1) x 10-4 M 1 s AH = 19.5(2) kcal mol" AS = -21(l)euandkH/fcD = 2.9(2) (75 °C) are in good agreement with the proposed mechanism with a metallacycle as transition state [164],... 

In the aldol-Tishchenko reaction, a lithium enolate reacts with 2 mol of aldehyde, ultimately giving, via an intramolecular hydride transfer, a hydroxy ester (51) with up to three chiral centres (R, derived from rYhIO). The kinetics of the reaction of the lithium enolate of p-(phenylsulfonyl)isobutyrophenone with benzaldehyde have been measured in THF. ° A kinetic isotope effect of fee/ o = 2.0 was found, using benzaldehyde-fil. The results and proposed mechanism, with hydride transfer rate limiting, are supported by ab initio MO calculations. 

The purpose of this review is to consider these intriguing findings and propose mechanisms with respect to the formation and possible biological action of CLA. 

C established the rate constants for the proposed mechanisms. With the intermediate N03 in steady state, the overall rate law is... 

Responding to Wilson s proposal, Shelef and Dalla Betta agreed that the lack of an isotope effect is not proof of the proposed mechanism with CO dissociative chemisorption as the RDS. The latter authors pointed out that infrared data indicate that for the catalyst they used, Ru, the surface is covered almost entirely by adsorbed CO, and not Cg as assumed by Wilson. 

Because of the enormous number of collisions occurring at any moment in a gas-phase reaction and the rapid formation and decomposition of reactive intermediates, reaction mechanisms can never be known with certainty. However, by observing reaction rates and comparing proposed mechanisms with experimental rates and with the overall stoichiometry, we can propose a mechanism that fits... 

It is difficult to reconcile the proposed mechanism with the observed low pre-exponential factor. Moreover, the isotope effects on the rate can be accomodated very simply on the assumption that the effect of dideuteration at the exocyclic and endocyclic C atoms on rate-limiting spin-non-conservative fragmentation of MP to MCP and N2 is additive in free-energy of activation - i.e. multiplicative in 1. The results of a least-squares fit of the experimental data [41, Table 3] are as follows ... 

The proposed mechanism with isonicotinic acid (Scheme 20) yields a rate law... 

Propose mechanisms with electron pushing for the following reactions, the first of which is catalytic. 

It is obviously critical to test these proposed mechanisms with psychophysical experiments. Of immediate interest is whether the lower number of functional olfactory receptor genes in humans than in rodents and subhuman primates is paralleled by lower psychophysical performance in odor detection and discrimination. 

Ruthenium-catalyzed coupling reactions reported by Murahashi, and a composite proposed mechanism with added nucleophile. 

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