Chemistry
The Impact of Isotopic Substitution on Reaction Rates
Quick fact
Deuterium, an isotope of hydrogen, has twice the mass of ordinary hydrogen. When a C–H bond is replaced by a C–D bond, the reaction can slow down by a factor of 6 to 10 or more—a dramatic change that helps chemists map out reaction pathways.
Why this is interesting
Imagine two identical molecules, except one contains a carbon atom twice as heavy as the other—yet the heavy one reacts slower. Why would a simple mass change affect how fast a chemical bond breaks?