Butyl - Tert-butyl Effect

Tert-butyl Effect

The tert-butyl substituent is very bulky and used in chemistry for kinetic stabilisation together with other bulky groups such as the related trimethylsilyl group. The effect that the t-butyl group exerts on the progress of a chemical reaction is called the tert-butyl effect.

This effect is illustrated in the Diels-Alder reaction below, where the tert-butyl substituent causes a reaction rate acceleration by a factor of 240 compared to hydrogen as the substituent.