The Smoluchowski approach to the kinetics of fluorescence quenching reaction in liquids is tested by comparing the results of molecular dynamics simulations for spherical molecules with the Smoluchowski--Collins--Kimball model and the Step Function Nonradiative Lifetime model. The reaction cross-sections used in the simulations are exactly the same as assumed in the models and the quencher concentration is very low. The discrepancies between the simulations and the models give a general indication on the scale of errors of the Smoluchowski approach. A large number of particles used (typically N = 681472) allow us to obtain quantitative results. The simulations show a decisive influence of the distribution function of the reagents, g_AB(r), on the accuracy of results. If the liquid structure is ignored (g_AB(r)\equiv 1) the discrepancies between the model and the simulations are large especially for a very short times for which the models fail to match simulations even qualitatively. An inclusion of the distribution function significantly improves the description of the quenching process. For short time stages of the quenching the model excellently agrees with the simulations, if the characteristic reaction time is long. If it is very short (the SCK model), significant discrepancies appear due to ballistic motion of the reactants but the quantitative agreement is still good. For a long time the model that takes into account the liquid structure is typically burdened with a few times smaller errors than the model that assumes g_AB(r)\equiv 1.

PACS numbers: 02.20.--w, 02.50.Ey, 02.70.Ns