[iScience]

"if the reaction is more downhill then we will have an earlier transition state and if we have a less downhill reaction/or a uphill reaction, then we will get a later transition state"


what is meant by "earlier" and "later" transition states?

[Dan]

This explains it well:

http://en.wikipedia.org/wiki/Hammond's_postulate#Interpreting_the_postulate

[spirochete]

"Early" means it looks like the reactants. "Late" means it looks like the products.

For transition states leading to reactive intermediates this generally means that relatively endergonic reactions are more selective. Technically a late transition state is not synonymous with selectivity, however.