Both lanes run the same balanced transformation, Substrate + Coupling partner → Product + Leaving group, promoted by an activator. Atom economy is a property of that balanced equation alone — it does not care whether the activator is catalytic or stoichiometric:
Atom Economy = MW(desired product) / Σ MW(all reactants) × 100%
What catalysis changes is how much of the promoting reagent ends up as waste. A catalyst is, by definition, regenerated at the end of each cycle — it binds, converts substrate to product, and returns to its original state, so the same molecules can turn over indefinitely:
Turnover Number (TON) = mol product formed / mol catalyst
Turnover Frequency = TON / time
A stoichiometric reagent has no such regeneration step: one activator molecule is spent per product molecule and reports directly to waste. That difference shows up in the E-factor, the mass of waste produced per mass of product — the metric process chemists actually optimize against:
E-factor = mass(waste) / mass(product)
E(catalytic) ≈ [LG + (loading%) · MW(activator)] / MW(product)
E(stoichiometric) ≈ [LG + MW(activator)] / MW(product)
- Leaving-group buttons — swap the reaction's intrinsic byproduct (water, HCl, or a bulky tosylate leaving group) and watch atom economy shift in both lanes identically, since it's a stoichiometry effect, not a catalysis effect.
- Catalyst loading — how many mol% of catalyst is present relative to substrate; lower loading means each catalyst molecule must turn over more times, and lowers the amortized activator waste in the catalytic E-factor.
- Activator molar mass — the "cost" of the promoting reagent itself; a heavy metal-based activator devastates the stoichiometric E-factor far more than the catalytic one, because catalysis only needs a trace of it.
This is exactly why green-chemistry process design favors catalytic C–H activation, hydrogenation and cross-coupling over older stoichiometric routes (e.g. stoichiometric Cr(VI) oxidants, stoichiometric organometallic couplings): same product, same intrinsic atom economy, but orders of magnitude less waste mass per kilogram of product.