The field of Green Chemistry has evolved over the decades. In the 1980s, the focus was on pollution control, with the publication of the 12 principles of green chemistry [1] in the late 1990s encouraging a more holistic approach, through to the 2010s, which has seen an explosion in the number of publications claiming to include green reaction processes [2]. Answering the question as to whether a reaction is genuinely ‘green’ is not straightforward and requires an objective method of measuring its environmental impact.
In order to assess the greenness of a reaction, a number of ‘green metrics’ have been developed, which allow chemists to quantify and qualify the environmental impact of their reactions and assist with the comparison of different routes/methods. Early green metrics focused largely on efficiencies in terms of mass inputs and outputs, but this has since expanded to incorporate a much more comprehensive and holistic approach.
The following references provide an excellent overview of available green chemistry metrics:
D. J. C. Constable, A. D. Curzons and V. L. Cunningham, Metrics to ‘green’ chemistry-which are the best?, Green Chem., 2002, 4, 521-527.
C. Jimenez-Gonzalez, D. J. C. Constable and C. S. Ponder, Evaluating the “Greenness” of chemical processes and products in the pharmaceutical industry-a green metrics primer, Chem. Soc. Rev., 2012, 41, 1485-1498.
R. C. McElroy, A. Constantinou, L. C. Jones, L. Summerton and J. H. Clark, Towards a holistic approach to metrics for the 21st century pharmaceutical industry, Green Chem., 2015, 17, 3111-3121.
To study this area in more depth, see Metrics
The CHEM21 project has developed a unified metrics toolkit to comprehensively evaluate the sustainability of chemical and bio-chemical reactions based on a series of key parameters (see Figure 1). Moving beyond the use of ‘mass based metrics’ alone, the toolkit uses a blend of both qualitative and quantitative criteria to assess how green a reaction is, as well as considering factors both upstream and downstream of the reaction itself. This ensures a truly holistic approach.
The rationale behind the toolkit and the methodology employed is now available in an open access publication [3]. As part of the background to this work CHEM21 performed a survey of available Green Chemistry metrics, which is accessible within the supplementary information of this paper.
To study this area in more depth, see CHEM21 metrics toolkit
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