Kinetic factors single pathway

Reaction coordinate diagrams, so often written as a single pathway between reactants and products on a two-dimensional canvas, are in fact much more complex and multidimensional. In order to truly understand how a chemical reaction occurs, all of the available kinetic and thermodynamic data should be known (i) What is the driving force for the reaction (ii) What are the elementary steps that lead from reactant to product (iii) What factors govern the heights of the activation barriers (iv) What are the structures of the intermediates (v) How and where are the bonds broken or made (vi) What is the stereochemistry of the reaction In order to answer these questions, a variety of experimental techniques must be used. The dependence of the rate and product distribution on pH, temperature, pressure, and solvent must also be examined. 

Selectivity in the oxidation of ammonia seems to be determined by the competition of NH3 and oxygen for a single type of active site, but the factors governing selectivity in the co-oxidation of ammonia and methane are obscure. The kinetics of HCN formation and of by-product formation should be examined under molecular beam conditions and over a wide temperature range so as to identify the important kinetic pathways. 

Because of the factors that reduce the amplitude in a presteady-state burst experiment and the difficulty in resolution of the product (or intermediates) from excess substrate, it is often desirable to use single-turnover methods. These experiments are performed with enzyme in excess over substrate to allow the direct observation of the conversion of substrates to intermediates and products in a single pass of the reactants through the enzymatic pathway. Unlike the presteady-state burst experiments, the kinetics are free of complications resulting from the steady-state formation of products, which limits the resolution of the burst kinetics and the detection of any intermediates above the background of excess substrates and products. 

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