Chemistry
How Isotope Effects Reveal Reaction Mechanisms in Kinetic Studies
Quick fact
Replacing a hydrogen atom with deuterium can slow a reaction by up to 7-fold or even more, because the heavier isotope lowers the vibrational zero-point energy and raises the activation barrier.
Why this is interesting
Imagine two identical reactions, one with a hydrogen atom and one with a deuterium atom—yet one runs slower. Why would swapping a single neutron change the reaction speed?