Rate Constants of Gasphase Unimolecular Reactions
Database "Rate Constants of Gasphase Unimolecular Reactions" was programmed within Delphi2 for Windows'95 as private commercial initiative by Dr. Nataliya Kruglyak and Prof. Yuri Kruglyak. See URLs about the authors below.
It is based on open literature data search and covers unimolecular reactions only. The Database contains now over 2000 entries and is open for editing and addition of new data.
A unimolecular reaction involves only one reactant molecule which undergoes chemical transformation. Isomerization reactions AB = BA and decay reactions AB = A + B are typical examples. Such a definition of unimolecular reaction can not define a formal kinetic law (reaction order) of corresponding chemical transformation. Both limits of formal kinetics - first order and second order reactions might occur depending upon the reaction conditions.
As it follows from experiments and theory unimolecular reactions undergo the first order kinetics for high pressure limit with rate constant kinf. Kinetics becomes the second order for low pressure limit with rate constant k0. In both limiting cases a rate constant is expressed in a form of the Arrhenius Rate law k = A(T)exp(-E/RT). Theory of unimolecular reactions shows that an effective rate constant k depends upon a pressure. Under low pressure conditions, P << kinf / k0, effective constant k is proportional to pressure, k = k0P. Its maximum value k = kinf is reached under high pressure conditions, P >> kinf / k0. Pressure P1/2 corresponding to k = kinf / 2 is traditionally taken as a border between low and high pressure regions. Lindemann' theory gives 1/k = 1/kinf + 1/k0P and, thus, P1/2 = kinf / k0.
In our database unimolecular reactions are divided on three types:
- Isomerization Reactions;
- Decay to Molecules;
- Decay to (Free) Radical(s).
Rate constants parameters are given in a form of the Arrhenius rate law for all temperature and pressure intervals studied. Rare exceptions are noted in the "Comments" window. Temperature T is given in Kelvins (K), Pressure P - in torrs, Energy E - in Kcal/mol with a few exceptions.
If a unimolecular reaction follows the first order (high pressure region) it is represented in the Database as AB = BA or AB = A + B; in a case of the second order (low pressure region) as AB + (M) = A + B + (M); when a reaction order is not determined or it is known that an order is an intermediate between the first and the second ones (transition pressure region) a reaction is represented as AB => BA etc.
Rate constants of the first order (and of intermediate one) are given in /c; the second order rate constants are given in cm3/mol/c.
"References" window gives a literature reference for each set of data.
"Comments" window may contain commentaries to a given set of data and method used to elaborate the rate constant parameters. It may also contain CAS Registry Numbers of Product(s) or Cambridge Soft Corporation Registry Number used in CS ChemFinder www-server DB at http://www.camsoft.com.
Delphi2 Navigator is used for searching DB by Formula, IUPAC Name, Synonyms, CAS Registry Number of a Reactant or its Products. Extensive "Help" support is provided.
Installation copy volume is 3.8 MB. Database requires x.x MB of disk space.
The Database can be purchased for xxxUSD. Prepayment is required. DB installation copy will be e-mailed you without any delay.
You are welcome to contact us via e-mail address below or kruglyak@farlep.net or by Fax/Voice Numbers
- +380-482-63 77 85
- +380-482-60 33 14.
Copyright © November 1999 Nataliya and Yuri Kruglyak
Send E-Mail to: quantum@farlep.net
This page created using the webpage creation facilities of Webspawner.
Copyright © 2000 Yuri Kruglyak. All Rights Reserved
WebSpawner Page Machine