Illustrated Glossary of Organic Chemistry

Microscopic reversibility: The mechanism of a reversible reaction is exactly the same (but reversed) for both the forward and backward version of the reaction. The transition states for each mechanism step are identical regardless of reaction direction.

Mechanism for Electrophilic Addition of HBr to 2-Methylpropene

Mechanism for E1 Dehydrohalogenation of 2-Bromo-2-methylpropane

The electrophilic addition of HBr to 2-methylpropene and E1 dehydrohalogenation of 2-bromo-2-methylpropane are reversible. These mechanisms demonstrate microscopic reversibility.