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In
physical chemistry , the Evans–Polanyi principle (also referred to as the Bell–Evans–Polanyi principle , Brønsted–Evans–Polanyi principle , or Evans–Polanyi–Semenov principle ) observes that the difference in
activation energy between two reactions of the same family is proportional to the difference of their
enthalpy of reaction .
This relationship can be expressed as
E
a
=
E
0
+
α
Δ
H
,
{\displaystyle E_{\text{a}}=E_{0}+\alpha \Delta H,}
where
E
0
{\displaystyle E_{0}}
is the
activation energy of a reference reaction of the same class,
Δ
H
{\displaystyle \Delta H}
is the
enthalpy of reaction ,
α
{\displaystyle \alpha }
characterizes the position of the
transition state along the
reaction coordinate (such that
0
≤
α
≤
1
{\displaystyle 0\leq \alpha \leq 1}
).
The Evans–Polanyi model is a
linear energy relationship that serves as an efficient way to calculate
activation energy of many reactions within a distinct family. The
activation energy may be used to characterize the
kinetic rate parameter of a given reaction through application of the
Arrhenius equation .
The Evans–Polanyi model assumes that the
pre-exponential factor of the
Arrhenius equation and the position of the
transition state along the
reaction coordinate are the same for all reactions belonging to a particular reaction family.
Carey, Francis, A.; Sundberg, Richard, J. (2007). Advanced Organic Chemistry (Part A: Structure and Mechanisms) (5th ed.). New York: Springer.
ISBN
978-0-387-44897-8 .
OCLC
154040953 . {{
cite book }}
: CS1 maint: multiple names: authors list (
link )
Dill, Ken A.; Bromberg, Sarina (2011). Molecular Driving Forces: Statistical Thermodynamics in Biology, Chemistry, Physics, and Nanoscience (2nd ed.). London: Garland Science.
ISBN
978-0-8153-4430-8 .
OCLC
660161826 .
Vinu, R.;
Broadbelt, Linda J. (2012). "Unraveling Reaction Pathways and Specifying Reaction Kinetics for Complex Systems". Annual Review of Chemical and Biomolecular Engineering . 3 (1): 29–54.
doi :
10.1146/annurev-chembioeng-062011-081108 .
ISSN
1947-5438 .
PMID
22468596 .