# Is there an example where interpreting reaction coordinate as time leads to an incorrect conclusion?

I have heard that we should not interpret the reaction coordinate in an energy diagram as time, but are there any situations in which we would arrive at an incorrect conclusion if we did so?

When I say interpreting reaction coordinate as time, I really mean as $\frac{\text{time so far}}{\text{total time for reaction}}$ (I would have written this instead of "time", but I'm not sure of a word or phrase for this).

• There's probably a monotonic mapping from reaction coordinate to time but there's no reason to believe this mapping is uniform or smooth. Also, it's not clear what you mean by "wrong conclusion." What conclusion can you draw from a reaction coordinate at all?
– Zhe
Jan 20 '18 at 13:12
• You can compute the free energy of a system as a function of a reaction coordinate. If you carry over that to time, the result is conceptually misleading. Thermodynamic calculations don't tell you about kinetics. Jan 21 '18 at 4:42
• @CurtF What does free energy plotted against time look like? Jan 21 '18 at 18:48
• A reaction coordinate is never time but a description of the distance between the reacting atoms as the reaction proceeds vs the energy. Time is not linear in this respect, i.e. the reaction moves with different speed at different points on the reaction coordinate. Jan 26 '18 at 13:56