The Hammett equation in organic chemistry describes a linear free-energy relationship relating reaction rates and equilibrium constants for many reactions involving benzoic acid derivatives with meta- and para-substituents to each other with just two parameters: a substituent constant and a reaction constant. This equation was developed and published by Louis Plack Hammett in 1937 as a follow up to qualitative observations in a 1935 publication.
The basic idea is that for any two reactions with two aromatic reactants only differing in the type of substituent, the change in free energy of activation is proportional to the change in Gibbs free energy. This notion does not follow from elemental thermochemistry or chemical kinetics and was introduced by Hammett intuitively.
Read more about Hammett Equation: Hammett Equation, Substituent Constants, Rho Value, Dominating Inductive Effects, Nonlinearity, Hammett Modifications, Estimation of Hammett Sigma Constants
Famous quotes containing the words hammett and/or equation:
“When a man’s partner is killed he’s supposed to do something about it. It doesn’t make any difference what you thought of him. He was your partner, and you’re supposed to do something about it.”
—Dashiell Hammett (1894–1961)
“A nation fights well in proportion to the amount of men and materials it has. And the other equation is that the individual soldier in that army is a more effective soldier the poorer his standard of living has been in the past.”
—Norman Mailer (b. 1923)