What does atom economy indicate?

Atom economy is a measure that indicates the efficiency of a chemical reaction in terms of how well it converts reactants into useful products while minimizing waste. Specifically, it is calculated using the formula:

Atom Economy = (Molar mass of desired products / Molar mass of all reactants) x 100%

This calculation reflects the percentage of the total mass of reactants that ends up as the desired product. A high atom economy means that a greater proportion of the reactants have been converted into useful products, which results in less waste being produced. This concept is particularly important in the field of green chemistry, where reducing waste and increasing efficiency can lead to more sustainable chemical practices.

The other options do not accurately represent what atom economy measures. The total mass of reactants is a basic property of the reaction but does not reflect efficiency or waste. The amount of energy required for a reaction relates to its enthalpy or thermodynamics rather than atom economy. The ratio of moles of reactants to products, while it can provide some insight into the stoichiometry of a reaction, does not take into account the actual mass of the substances involved, which is central to the idea of atom economy.