Reversible adiabatic change chemical reactions

A spontaneous change occurs naturally (by itself) under specified conditions, without an ongoing input of energy from outside the system. In particular, a chemical reaction proceeding toward equilibrium is an example of a spontaneous change. For a thermodynamically reversible adiabatic process a quantitative statement of the second law can be formulated as [9] ... 

In adiabatic reactions, the chemical change occurs on the same energy hypersurface (see Sect. 1.2). Most adiabatic photoreactions are proton transfer reactions. All reactions of that sort are reversible insofar as, following deactivation, very fast reverse reactions drive the system back to its original composition so that no permanent change occurs [26b]. 

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