How can a selective catalyst change which products form in a chemical reaction?

A selective catalyst changes which products form in a chemical reaction by preferentially accelerating one specific reaction pathway over others that may be occurring simultaneously.1

When a substance or combination of substances can undergo multiple reactions to yield different products, the distribution of those products is determined by the relative rates of the competing reactions. By choosing an appropriate catalyst, chemists can selectively speed up one of these reactions to such an extent that it practically excludes the formation of other potential products.1

This selectivity is a cornerstone of many industrial processes, such as the use of specific transition metal catalysts to direct the transformation of organic molecules toward desired outcomes like polymerization or hydrogenation. While the catalyst significantly influences the rate at which equilibrium is reached for the chosen pathway, it does not change the position of the equilibrium itself.213