Ambivalent Lewis structures the transition-state limit

1 AMBIVALENT LEWIS STRUCTURES THE TRANSITION-STATE LIMIT 

The NTS criterion (10.5) may serve as a useful alternative to the ETS saddle-point criterion for the case of barrierless reactions, and the two criteria will be compared in what follows. 

As simple prototype examples, let us first consider two elementary gas-phase reactions that were previously encountered in Problem 4.1, both leading to production of formaldehyde (H2CO, product species Pj). The first involves bimolecular reaction of dihydrogen and carbon monoxide (H2- CO, reactant species Rn), namely. 

The second involves unimolecular isomerization (hydride transfer) of hydroxymethy-lene (HCOH, reactant species Rni), namely, 

A sample Gaussian input file is shown in I/O-lO.l illustrating use of the QST3 method to find the optimized TSi ni for hydroxymethylene decomposition (10.8), with input specification of optimized structures for Rm, Pi and an initial guess 

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Ambivalent Lewis Structures The Transition-State Limit 233... 

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