Gibbs energy diagram

Gibbs energy diagram:

 A diagram showing the relative standard Gibbs energies of reactants, TRANSITION STATEs, reaction INTERMEDIATEs, and products in the same sequence as they occur in a CHEMICAL REACTION. These points are often connected by a smooth curve (a “Gibbs energy profile,” still commonly referred to as a
“free energy profile”), but experimental observation can provide information on relative standard Gibbs energies only at the maxima and minima and not at the configurations between them. The abscissa expresses the sequence of reactants, products, reaction intermediates, and transition states and is usually undefined or
only vaguely defined by the REACTION COORDINATE
(extent of bond breaking or bond making). In some adaptations, however, the abscissas are explicitly defined as BOND ORDERs, Bronsted exponents, etc. Contrary to statements in many textbooks, the highest point on a Gibbs energy diagram does not necessarily
correspond to the transition state of the RATE-LIMITING
STEP. For example, in a STEPWISE REACTION consisting
of two reaction steps
1. A + B C
2. C + D → E