Programs are simple in use. Process of calculation is absolutely transparent and indicative. Researcher can completely checks process of calculation, can observe contributions of various motions to reaction rate. Additional utilities allow to be integrated efficiently with Gaussian that simplifies process of joint calculation. The analysis of contributions of varios partition functions, will allow to make deduction about influence of the nature of reagents to kinetic constant of chemical reaction, will allow to explain experimental values. Gained informations will allow to understand better chemical interactions and to influence process. Account of an internal rotation of the symmetric and asymmetrical top, essentially increment quality of calculation.

Let's view chemical reaction figured on the scheme:

For accurate calculation of Arhenius factor and rate constants, it is necessary to consider internal rotation of four tops, specified on 2-methyl-2-nitrobutane . Two tops are nonsymmetric (top1, top2), two are symmetric (top3, top4), ChemRate programs suit, allow to consider the contribution of internal rotation of two types of tops.

Top1 -Potential enegry of internal rotation of group (B3LYP 6-31G(d))

Top2 - Potential energy of internal rotation of group (B3LYP 6-31G(d))

Top3 - Potential energy of internal rotation of group (B3LYP 6-31G(d))

Calculated values of preexponential factor for reaction on scheme, in view of only vibrational and external rotational partition functions: Lg(A)=12.82 1/c

Calculated values of preexponential factor for reaction on scheme, in view of only internal rotation for top2, vibrational and external rotational partition functions: Lg(A)=13.40 1/c

Calculated values of preexponential factor for reaction on scheme, in view of only internal rotation for top1, top2, top3, top4, vibrational and external rotational partition functions: Lg(A)=13.30 1/c

Experimental value: Lg(A)=13.30 1/c *

* Dubikhin, V.V.; Nazin, G.M.; Sokolov, D.N.; Manelis, G.B. Thermal decomposition of mononitroalkanes. Bull. Acad. Sci. USSR Div. Chem. Sci. (Engl. Transl.)