Organic Mechanisms. Xiaoping Sun

Organic Mechanisms - Xiaoping Sun


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rel="nofollow" href="#ulink_36cdd569-3ae3-561b-a1c2-b2befc3e231f">Equation 1.25, we have

      If one of the reactants (such as B) in Equation 1.5 (the bimolecular reaction: A + B ➔ P) is in large excess (typically 10–20‐folds, i.e., [B]0/[A]0 = 10–20), the change in molar concentration of reactant B in the course of the reaction can be neglected ([B] ~ [B]0) [2]. The rate law (Eq. 1.18) becomes

      Let k′ = k[B]0 (the observed rate constant). We have

      The reaction becomes pseudo first order. The integrated rate law is

      1.4.2 Reactive Intermediates and the Steady‐State Assumption

      It is tedious to obtain the accurate solutions of the above simultaneous differential equations. Appropriate approximations may be employed to ease the situation [2].

      With the help of the steady‐state approximation, the dependence of concentrations of all the substances in Reaction 1.28 on time can be obtained readily [2].

      [X]0 is the initial concentration of X.

      From Equation 1.30 (rate equation for Y) and Equation 1.32 (steady‐state assumption for Y), we have