Passing to the limit of an infinite reaction rate in a slow-fast system of chemical reactions provides a quasi-steady state approximation (QSSA) of these systems. In case of reactions with detailed balance condition, this approximation includes a dimension reduction to a smaller state space. We show that the limit dynamics carry an entropic gradient structure on this smaller space. where R s , R f ∈ N are the numbers of fast and slow reactions, respectively, with R := R s + R f ≤ I. In general, subscripts or superscripts s, f, c denote slow, fast or conserved quantities and parameters of the system. Here, k r > 0 and κ r k r > 0 are the (unscaled) forward and backward reaction rates, , and γ r = α r − β r are the stoichiometric vectors. We write C r (c) := c αr − κ r c βr as a shorthand and assume that γ 1 , · · · , γ R are linearly independent and that all parameters are independent of ε. In particular, system (1) satisfies detailed balance, cf. [1,2].