The Eyring equation (occasionally also known as Eyring–Polanyi equation) is an equation used in chemical kinetics to describe the variance of the rate of a chemical reaction with temperature. It was developed almost simultaneously in 1935 by Henry Eyring, Meredith Gwynne Evans and Michael Polanyi.
The Eyring Equation, developed by Henry Eyring in 1935, is based on transition state theory and is used to describe the relationship between reaction rate and temperature. It is similar to the Arrhenius Equation , which also describes the temperature dependence of reaction rates.
Arrhenius plots are often used to analyze the effect of temperature on the rates of chemical reactions. For a single rate-limited thermally activated process, an Arrhenius plot gives a straight line, from which the activation energy and the pre-exponential factor can both be determined.
An Eyring plot allows the activation parameters ∆S‡ and ∆H‡ to be determined from the temperature dependence of the rate constant; the dotted part of the line represents an extrapolation. Initial attack by the entering group at a square planar Pt(II) centre is from above or below the plane.
Convex Arrhenius plots and their interpretation Figure 4: Concave and convex Eyring Plot In the broad field of kinetics, not restricting consideration to enzyme kinetics, when nonlinear Arrhenius or Eyring plots can be observed, they are almost always concave. A concave Arrhenius or Eyring plot can be attributed to several factors.
Based on transition state theory, the Eyring equation can also be used to analyze kinetic data: ln(k h/k B T) = ΔS*/R - ΔH*/RT Plotting ln(k h/k B T) versus 1/T gives a line with slope of -ΔH*/R and intercept of ΔS*/R. As a check the difference between the activation energy and enthalpy should be equal to RT.
The Eyring relationship was formulated from quantum mechanics principles, as discussed in Glasstone et al. , and is most often used when thermal stress (temperature) is the acceleration variable.However, the Eyring relationship is also often used for stress variables other than temperature, such as humidity.
the slope of a plot of ln k vs l/T gives Ea/R and the intercept gives ln (A) We can translate between the Eyring and Arrhenius languages, but this is a bit tricky because the Arrhenius equation makes ln (k) linear in (1/T) while the Eyring equation does not. At some temperature T in the middle of the range studied we determine the
Eyring Plots: Mechanism Determination in Ligand Substitution Reactions. In the case of ligand substitution in transition metal complexes, there are really four possible mechanisms. The two we have discussed this far represent the extremes—a D (dissociative) mechanism or an A (associative) mechanism. ...