Hammett equation
E743329
linear free-energy relationship
physical organic chemistry concept
quantitative structure–reactivity relationship
The Hammett equation is a fundamental linear free-energy relationship in physical organic chemistry that quantitatively correlates reaction rates and equilibria with the electronic effects of substituents on aromatic compounds.
Statements (48)
| Predicate | Object |
|---|---|
| instanceOf |
linear free-energy relationship
ⓘ
physical organic chemistry concept ⓘ quantitative structure–reactivity relationship ⓘ |
| appliesBestTo | meta- and para-substituted benzoic acid derivatives ⓘ |
| appliesTo |
benzoic acid derivatives
ⓘ
reactions involving aromatic substituents ⓘ substituted aromatic compounds ⓘ |
| assumes |
constant reaction mechanism across substituents
ⓘ
dominant electronic effects of substituents ⓘ |
| basedOn | reference reactions of substituted benzoic acids ⓘ |
| category |
Chemical kinetics
ⓘ
Physical organic chemistry theories ⓘ |
| correlates |
electronic effects of substituents
ⓘ
equilibrium constants ⓘ reaction rates ⓘ |
| describes |
linear relationship between log(K) and sigma
ⓘ
linear relationship between log(k) and sigma ⓘ |
| developedBy | Louis Plack Hammett NERFINISHED ⓘ |
| field |
organic chemistry
ⓘ
physical organic chemistry ⓘ |
| hasKeyConcept | linear correlation between structure and free energy changes ⓘ |
| hasMathematicalForm |
log(K/K0) = ρσ
ⓘ
log(k/k0) = ρσ ⓘ |
| hasVariant |
dual-parameter Hammett relationships
ⓘ
sigma-minus (σ⁻) constants ⓘ sigma-plus (σ⁺) constants ⓘ |
| introducedIn | 1937 ⓘ |
| involvesEffect |
inductive effects
ⓘ
resonance effects ⓘ |
| involvesQuantity |
equilibrium constant K
ⓘ
rate constant k ⓘ standard free energy change ΔG° via K ⓘ |
| lessAccurateFor | strongly resonance-interacting ortho substituents ⓘ |
| namedAfter | Louis Plack Hammett NERFINISHED ⓘ |
| quantifies | sensitivity of a reaction to substituent electronic effects ⓘ |
| relatedTo |
Taft equation
NERFINISHED
ⓘ
Yukawa–Tsuno equation NERFINISHED ⓘ linear free-energy relationships ⓘ |
| relates |
reaction constant rho to sensitivity to substituent effects
ⓘ
substituent constant sigma to reactivity ⓘ |
| usedFor |
analyzing substituent effects
ⓘ
correlating equilibrium constants ⓘ predicting relative reaction rates ⓘ |
| usedIn |
design of organic molecules with tuned reactivity
ⓘ
mechanistic studies of organic reactions ⓘ structure–reactivity correlation studies ⓘ |
| usesParameter |
Hammett sigma constant
NERFINISHED
ⓘ
reaction constant rho ⓘ |
Referenced by (2)
Full triples — surface form annotated when it differs from this entity's canonical label.