Green reaction mass efficiency

A Microsoft Excel (Version 5.0 or higher) spreadsheet template form has been developed which allows the calculation of the complete reaction mass efficiency (RME) according to equation (4.1) and raw material cost (RMC) for any chemical transformation. Lines are numbered and line instructions are embedded in the same manner as a personal income tax form. Green metrics are evaluated to determine the greermess of the experiment in a rigorous quantitative way and to determine the bottom line cost of carrying out the experiment. Formula entries are inserted in appropriate cells to facilitate computation. Any... 

Yield and other mass-related metrics such as atom economy, reaction mass efficiency and mass intensity have been examined by Constable et al with regard to their significance concerning greenness and costs. The importance of using a (product) concentration term, which can be mass intensity or mass index, is additionally emphasized by Laird et al This is in compliance with Winterton, who in his twelve more green chemistry principles demands the establishment of full mass balances. 

Quantitative evaluation of chemical processes in terms of environmental impact and eco-friendliness has gradually become a topic of great interest since the original introduction of the atom economy (AE) by Trost [1], and the E-factor by Sheldon [2]. Since then, other indexes have been proposed for the green metrics of chemical processes, such as effective mass yield (EMY) [3], reaction mass efficiency (RME) [4] and mass intensity (MI) [5], along with unification efforts [6, 7] and comparisons among these indexes [8]. 

Because reaction mass efficiency includes all the mass used for a given reaction (whether or not it includes or excludes water), and includes yield, stoichiometry, and atom economy, we believe that this metric is the most helpful metric for chemists to focus their attention on how far from green a given reaction or reaction scheme may be. 

However, the true greenness of this reaction remained far from being ideal, as the necessity to prepare initially the arylboronic acids (or their derivatives) as nucleophilic starting material and to recycle (or to eliminate) the associated waste thereafter violate several of the TPGC. Hence this not only contradicts the concept of atom economy [35], but also increased Sheldon s environmental impact factor E (E = kgwaste/kgproduct) [36]. As a consequence, this resulted in a decrease in the value of the reaction mass efficiency (RME) forthe Suzuki-Miyaura reaction. The value RME = 1 characterizes an absolutely green reaction, but all reactions with RME >0.618,... 

The number of green metrics subsequently proliferated [20-23]. They can be divided into two types (i) metrics that are a refinement of the AE concept and (ii) metrics that are variations of the E factor (see Figure 1.2). Examples of the former are reaction mass efficiency (RME) and carbon efficiency (CE) introduced by Constable and coworkers [24] at GlaxoSmithKline (GSK). The RME is defined as the mass of... 

Andraos, J. (2007) On the Use of Green Metrics in the Undergraduate Organic Chemistry Lecture and Laboratory to Assess the Mass Efficiency of Organic Reactions. Journal of Chemical Education, 84, 1004-1010. 

Solvents are not included in the calculation. Like effective mass yield, carbon efficiency strives to make a value judgment on the relative importance of various wastes. Elimination of water from a molecule would not count against the carbon efficiency of a reaction, but it would give a decreased atom economy. By not including all wastes, carbon efficiency is not as strict as most green metrics. Of course, all metrics have their shortcomings and carry their own assumptions. 

---