Atom economy

Good atom economy means most of the atoms of the reactants are incorporated in the desired products and only small amounts of unwanted byproducts are formed, reducing the economic and environmental impact of waste disposal.

Atom economy is a different concern than chemical yield, because a high-yielding process can still result in substantial byproducts.

Examples include the Cannizzaro reaction, in which approximately 50% of the reactant aldehyde becomes the other oxidation state of the target; the Wittig and Suzuki reactions which use high-mass reagents that ultimately become waste; and the Gabriel synthesis, which produces a stoichiometric quantity of phthalic acid salts.

Catalytic hydrogenation comes the closest to being an ideal reaction that is extensively practiced both industrially and academically.

Atom economy can be improved upon by careful selection of starting materials and a catalyst system.

Poor atom economy is common in fine chemicals or pharmaceuticals synthesis, and especially in research, where the aim to readily and reliably produce a wide range of complex compounds leads to the use of versatile and dependable, but poorly atom-economical reactions.

For example, synthesis of an alcohol is readily accomplished by reduction of an ester with lithium aluminium hydride, but the reaction necessarily produces a voluminous floc of aluminum salts, which have to be separated from the product alcohol and disposed of.

As it is a significant goal of green chemistry to maximize the efficiency of the reactants and minimize the production of waste, D must either be found to have use, be eliminated or be as insignificant and innocuous as possible.