# Typical values of activation energies?

Where can I find typical values of the Arrhenius activation energy for arbitrary reactions? I only want to have orders of magnitude estimates, but so far I have not been able to find any good resource that lists activation energies for different types of reactions.

There are tons of papers in which people determine precise values for very specific reactions, but I am looking for a kind of database or reference that has a large collection of values. In particular, those for biochemical reactions would be useful to have.

• You can roughly estimate based on the expected half-life and the Eyring equation. See: chemistry.stackexchange.com/questions/61602/…
– Zhe
Apr 5 '17 at 21:25
• That is because there are no typical values, and this is why only individual values are quoted. Fast reactions have small activation energies, slow ones large ones, but what is fast, slow and small or large is subjective. What is true, however, is that because of the exponential dependence of rate constants (1/rate const = lifetime) relatively small differences in activation energy cause a huge difference in reaction lifetime as pointed out by @Zhe. Apr 6 '17 at 14:35

NIST has an kinetics database which might be helpful to you.

In there own words:

The NIST Chemical Kinetics Database includes essentially all reported kinetics results for thermal gas-phase chemical reactions. The database is designed to be searched for kinetics data based on the specific reactants involved, for reactions resulting in specified products, for all the reactions of a particular species, or for various combinations of these. In addition, the bibliography can be searched by author name or combination of names. The database contains in excess of 38,000 separate reaction records for over 11,700 distinct reactant pairs. These data have been abstracted from over 12,000 papers with literature coverage through early 2000.

Rate constant records for a specified reaction are found by searching the Reaction Database. All rate constant records for that reaction are returned, with a link to "Details" on that record.

Each rate constant record contains the following information (as available):

a. Reactants and, if defined, reaction products;
b. Rate parameters: $$A$$, $$n$$, $$\frac{E_a}{R}$$, where $$k = A(\frac{T}{298})^ne^{[-(\frac{E_a}{R})(\frac{1}{T})]}$$, where $$T$$ is the temperature in Kelvins;
c. Uncertainty in $$A$$, $$n$$, and $$\frac{E_a}{R}$$, if reported;
d. Temperature range of experiment or temperature range of validity of a review or theoretical paper;
e. Pressure range and bulk gas of the experiment;
f. Data type of the record (i.e., experimental, relative rate measurement, theoretical calculation, modeling result, etc.). If the result is a relative rate measurement, then the reaction to which the rate is relative is also given;
g. Experimental procedure, including separate fields for the description of the apparatus, the time resolution of the experiment, and the excitation technique. A majority of contemporary chemical kinetics methods are represented.

It has a simple reaction search feature as well as an advanced database search feature which is quite intuitive to use.