Bell–Evans–Polanyi principle

The linear relation between energy of activation ( $E a$ ) and enthalpy of reaction ( $Δ H r$ ) sometimes observed within a series of closely related reactions.

$E a = A + B Δ H r$

Source:

PAC, 1994, 66, 1077 (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1088