## Wikipedia - Free-energy relationship (en) Wikipedia - Hammett-yhtälö (fi) Wikipedia - Relación de energía libre (es) Wikipedia - 自由エネルギー関係 (ja) linear free-energy relation

Also contains definition of: linear Gibbs energy relation
https://doi.org/10.1351/goldbook.L03551
A linear correlation between the logarithm of a @O04322@ or @E02177@ for one series of reactions and the logarithm of the @O04322@ or @E02177@ for a related series of reactions. Typical examples of such relations (also known as linear Gibbs energy relations) are the @B00746@, and the @H02732@.
The name arises because the logarithm of an @E02177@ (at constant temperature and pressure) is proportional to a standard @F02515@ (Gibbs energy) change, and the logarithm of a @O04322@ is a linear function of the @F02515@ (Gibbs energy) of @A00093@.
It has been suggested that this name should be replaced by linear Gibbs energy relation, but at present there is little sign of acceptance of this change. The area of physical organic chemistry which deals with such relations is commonly referred to as 'Linear Free-Energy Relationships'.