Double dagger symbol

Here Z represents the reaction products. M is the transition state the double dagger symbol will always signify a quantity or structure relating to the transition state. Scheme I incorporates the equilibrium assumption by writing the conversion of the initial state into the transition state as an equilibrium. This assumption then allows us to apply statistical mechanics to the rate problem making use of Eq. (5-32), we have... 

Transition state theory treats a reacting system thermodynamically. Let us again take a bimolecular reaction between A and B. Transition state theory assumes that as A and B collide and start to react, they form a species called the activated complex, which corresponds to the A-B adduct at the peak of the energy hill lying between reactants and products. This activated complex is thus in a transition state and can either fall back to reactants or go on to form products. The activated complex is normally indicated with a double dagger symbol, AB. The reaction can thus be given as... 

In stepwise reactions, the double dagger symbol,, is used to indicate the rate-limiting step when it is known. 

Finally, in a number of cases, the double dagger symbol (tt) is used in Tables A.l and A.2 to refer the reader to the full versions of these tables [9,10]. 

Unlike the reactants or products, a transition state is unstable and cannot be isolated. It is not an intermediate, because an intermediate is a species that exists for some finite length of time, even if it is very short. An intermediate has at least some stability, but the transition state is a transient on the path from one intermediate to another. The transition state is often symbolized by a superscript double dagger ( ), and the changes in variables such as free energy, enthalpy, and entropy involved in achieving the transition state are symbolized AG, A//, and AS. AG is similar to Ea, and the symbol AG is often used in speaking of the activation energy. 

Nevertheless, one may write a statement resembling an equilibrium-constant expression, relating the activities or, approximately, the concentrations of the reactants and the activated complex (represented by the double-dagger or Cross of Lorraine symbol t) ... 

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