Deprotonation Gibbs free energy

Activated complexes involved in lithium amide deprotonation of 2 have been determined to contain one molecule of 2. Gibbs free energy difference between the two most stable TSs at 298 K. 

DFT calculations about the reaction mechanism showed that the most favorable one is that shown in Scheme 34. The Gibbs free energy in THF solution (in parentheses) is referred to that of the deprotonated species [Re(OTf)(CO)3(N-MeIm)2] (structure I, Scheme 34) and Af-Melm. The reaction starts with loss of triflate from I to give intermediate Ila in which... 

Fig. 8 The six lowest calculated energy spectra for deprotonated [dGMP-dCMP]- compared with IRMPD experiment. The energies listed are Gibbs free energies in kcal/mol relative to the ground state structure [70]...

As above stated, the reaction steps in the anionic mechanism take place in reverse order than in the cationic mechanism (Fig. 5.8). Thus, in the anionic mechanism the deprotonation of the alkyne by the external base in complex 2 occurs first, followed by the iodide-for-phosphine substitution. The Gibbs energy profile obtained for the copper-free Sonogashira reaction with phenylacetylene (R = H) through the anionic mechanism is shown in Fig. 5.10. 

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