Atom Economy Calculator
Calculate the atom economy of a chemical reaction.
Enter the molecular weight of the desired product and all byproducts to see how efficiently atoms are used.
Atom economy, introduced by Barry Trost in 1991, measures what fraction of the atoms in the reactants end up in the desired product rather than in waste byproducts. It is one of the twelve principles of green chemistry and a key metric for sustainable chemical process design.
Atom Economy = (MW of desired product / sum of MW of all products) x 100%
A reaction that produces only the desired product and no byproducts has 100% atom economy. An addition reaction (A + B → AB) always achieves 100% atom economy because all atoms go into one product.
A substitution reaction is typically worse. For example, a Grignard reaction that produces the target alcohol plus magnesium halide byproduct might show 60-70% atom economy, since a significant portion of the atomic mass ends up in the salt that gets washed away.
Common atom economy ranges by reaction type:
- Addition reactions: 100% (no byproducts by definition)
- Rearrangement reactions: 100%
- Substitution reactions: 10-80%, depending on byproduct mass
- Elimination reactions: often low — a small molecule is lost as waste
- Condensation reactions: variable, often 85-95%
Atom economy is not the same as yield. A reaction with 100% atom economy but 50% yield still wastes half the material. Industrial chemists optimize both together.
Barry Trost won the Presidential Green Chemistry Challenge Award partly for developing palladium-catalyzed reactions with high atom economy that replaced older, wasteful syntheses of pharmaceutical intermediates.