Calculate the RME of any chemical reaction from the actual masses of reactants and the isolated product. A single number that captures atom economy, yield, and stoichiometric efficiency together — results update live as you type.
Reaction Mass Efficiency (RME) is a practical green chemistry metric that measures what fraction of the total mass of reactants is actually converted into the desired product. Unlike atom economy, which is calculated from the balanced equation alone, RME uses the actual masses weighed out in the lab — so it automatically captures the combined effect of atom economy, reaction yield, and any stoichiometric excess in a single number.
| Symbol | Term | Units |
|---|---|---|
| $\text{RME}$ | Reaction Mass Efficiency | % (0–100); ideal value = 100% |
| $m_{\text{product}}$ | Mass of desired product actually isolated | g (or kg) |
| $\sum m_{\text{reactants}}$ | Total mass of all reactants used (excluding solvents, catalysts, and workup materials) | g (or kg) |
Solvents, catalysts, and workup reagents are not included in the RME denominator — they are captured by E-factor and PMI. RME is a reactant-only metric. A higher RME is always better.
| Reaction type / scenario | Typical RME | Key driver |
|---|---|---|
| Addition / Cycloaddition with high yield | 75–95% | High atom economy and good yield combine favourably |
| Condensation (e.g. esterification, amide bond) | 55–75% | Small molecule lost as by-product lowers atom economy |
| Substitution with stoichiometric leaving-group reagent | 30–60% | Heavy leaving group wasted; excess reagent common |
| Reduction (LiAlH₄ or NaBH₄, stoichiometric) | 20–50% | Heavy reductant contributes to denominator |
| Oxidation with stoichiometric oxidant | <30% | Heavy metal oxidants dominate reactant mass |
| Catalytic hydrogenation (H₂, metal catalyst) | 80–98% | H₂ is light; catalyst not consumed and not counted |
| Metric | What it measures | Stage |
|---|---|---|
| Atom Economy (AE) | Theoretical fraction of reactant MW in desired product (balanced equation only; no yield or excess) | Design |
| % Yield | Fraction of the theoretical product actually isolated, based on the limiting reagent | Experimental |
| RME (Reaction Mass Efficiency) | Fraction of total reactant mass converted to desired product — captures AE + yield + stoichiometry together | Experimental |
| E-factor | Mass of all waste (including solvents) per mass of product — full process scope | Experimental |
| PMI (Process Mass Intensity) | Total mass of all inputs per mass of product; PMI = E-factor + 1 | Experimental |
Enter each reactant with its actual mass used. Do not include catalysts or solvents — catalysts are not consumed, and solvents are not incorporated into the product. Use E-factor or PMI for a full process mass assessment.
| Reactant name | Formula (optional) | Mass used (g) | % of total |
|---|
Enter the actual mass isolated for the desired product. Add any characterised by-products for a complete mass-balance check — only the desired product mass contributes to the RME numerator.
| Compound name | Formula (optional) | Mass (g) | Role | % of reactants |
|---|
| Compound | Role | Formula | Mass (g) | % of Σ reactants | Visual |
|---|---|---|---|---|---|
| Enter reactants and at least one desired product above to see breakdown. | |||||
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