Dissipative reactive systems representing chain reactions have been considered. The contraction in the phase space is accounted for by means of the centre manifold asymptotic expansion. This expansion explicitly yields the equations of state for the fast-relaxing degrees of freedom with the slow variables as order parameters in the sense of Haken. It has been shown that the Gaussian width for the time-independent factor of the probability density is a measure of the degree of enslaving of the fast-state variables to the slow degree of freedom. The autonomous relations for the fast variables, as obtained from the centre manifold expansion, are in accord with previous findings which make use of the computational singular perturbation method to justify and obtain the steady-state approximated adiabatic elimination of the fast-relaxing intermediate concentrations. The term ‘adiabatic elimination’ indicates in this context that the slowly relaxing degrees of freedom are regarded as the order parameters determining the kinetics of the system and that the concentration of the intermediates is enslaved to the order parameters. The centre manifold stochastic description is in perfect agreement with the macroscopic phenomenological description of the overall kinetics.