Kinetic control of product

Thermodynamic Versus Kinetic Control of Product Distributions. 228... 

The crux of an editing mechanism is the formation of a high-energy intermediate that is unstable with respect to hydrolysis (equation 13.14). This allows an element of kinetic control of product formation to be introduced the intermediate is at a branch point in the reaction pathway so that it may be channeled either to further synthesis or to hydrolytic products. 

Wicke and Elgert studied the mode of a-methylstyrene placement in chains polymerized with butyllithium in tetrahydrofuran. They called attention to the possibility of various addition and depropagation rates for isotactic and syndiotactic monomer placement. Isotactic attachment is harder to form, and easier to decompose. For reversible processes this circumstance must be manifested at higher temperatures by thermodynamic, and at lower temperatures by kinetic, control of product stereoregularity [363],... 

Sulphonyl chlorides may be obtained by the reaction of some aliphatic compounds with a mixture of sulphur dioxide and chlorine, under conditions which permit the formation of radicals (equation 139)299,530-533. Usually a mixture of products is formed with amounts of each product being determined by the stabilities of the intermediate alkyl radicals. Thermodynamic or kinetic control of products may be exercized by control of the reaction temperature. 

In general, the preferential formation of one product because the free energy of activation leading to its formation is lower than that for another product, and therefore the rate of its formation faster, is called kinetic control of product formation. (See also Section 13.10A.)... 

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