Table 2.

Examples of green chemistry metrics applied to organic synthesis.

Parameter	Formula	Short Characteristics	Comments	Ref.
Carbon Efficiency (CE)	$\begin{array}{l}A+B\to D\\ \%CE=\left(\frac{\text{amount of carbon in prouct D}}{\text{total carbon presented in reactants}}\right)\times 100\end{array}$	It is used to estimate the percentage of carbon in the reagents used in organic synthesis that remain in the final desired product	This parameter is dedicated to evaluation of the greenness of organic synthesis based solely on carbon accounting	[26,39]
	$\begin{array}{l}A+B\to D+F\\ \%CE=\left(\frac{\text{no. of moles of D}\times \text{no. of carbon in D}\times \text{100}}{\text{moles in A}\times \text{carbon in A}+\text{moles in B}\times \text{carbon in B}}\right)\end{array}$
Effective Mass Yield (EMY)	$\%EMY=\frac{\text{mass of final product}}{\text{mass of hazardous and toxic reagents}}$	This parameter quantifies a percentage of the final product in all reagents and materials used in organic synthesis	Reagents having low or very low environmental impact (e.g., sodium chloride or acetic acid) are excluded from calculation of EMY	[40,41]
Mass Intensity (MI)	$\begin{array}{l}\left[\frac{kg}{kg}\right]MI=\frac{\text{total mass used in a process}}{\text{mass of final product}}\\ \text{Mass productivity}=\frac{\text{1}}{MI}\times \text{100}\end{array}$	The MI takes into account reaction efficiency, stoichiometry, amount of solvents, all reagents and auxiliary substances used in synthesis.	This parameter has a value of 1 for an ideal synthesis, in which the total mass of input is equal to the mass of product	[26,39]
Reaction Mass Efficiency (RME)	$RME=\frac{1}{1+E_m}$ where Em is a value of E-factor based on mass	The RME factor is inversely related to the overall E-factor described by Sheldon. The RME offers a better and easy way of identification of the best or the worst reactions that have influence on whole industrial process or synthesis.	This parameter was described very precisely by Andraos and Sayed (2007). The final version of RME equation depends on conditions of reaction or process (recovery of reaction solvents or post-reaction materials). This parameter is most effective in efforts to reduce waste at the intrinsic and global level	[39,42,43,44,45,46]
	$RME=(\epsilon )AE\frac{1}{SF}\left[\frac{1}{1+\frac{\epsilon AE(c+s+w)}{SF{m}_{cp}}}\right]$ where: —reaction yield; AE—atom economy; SF—stoichiometric factor; c—the mass of reaction catalyst; s—the mass of reaction solvent; w—the masses of all other post-reaction materials; mcp—the mass of the collected target product
Atom Utilization (AU)	$\%AU=\frac{\text{mass of the final product}}{\text{total mass of all the substances produced}}$	This parameter defines percentage ratio of the mass of final product to the mass of all products (final product and byproducts) obtained in synthesis. The solvents are excluded from calculations	It provides fast and simple evaluation of the greenness of a process or individual reaction in terms of produced waste. Nowadays it is seldom used	[39,47]
Solvent and catalyst environmental impact parameter (f)	$\text{f}=\left(\frac{{\displaystyle \sum \begin{array}{l}\text{mass of reaction and postreaction solvents}\\ \text{and materials}+\text{mass of catalysts used}\end{array}}}{\text{mass of final product}}\right)$	Evaluation of this parameter takes into account actual masses of materials used in the process	This parameter has a value of 0 only if all materials (solvents, catalysts etc.) used in the process or in individual step of synthesis are recycled, recovered or eliminated. In every other case, f > 0	[42,43,44,48]
Stoichiometric Factor (SF)	$SF=\text{1}+\left(\frac{\left(AE\right){\displaystyle \sum \text{mass of excees reagents/chemicals}}}{\text{expected product mass at 100\% yield}}\right)$	This parameter is calculated in case of syntheses in which one or more reagents are used in excessive amount	The SF has a value of 1 for stoichiometric reactions. If the reaction is nonstoichiometric the SF > 1