Inclusion of Environmental Impact Parameters in Radial Pentagon Material Efficiency Metrics Analysis: Using Benign Indices as a Step Towards a Complete Assessment of “Greenness” for Chemical Reactions and Synthesis Plans

A new benign index (BI) parameter is developed and applied to assess the overall “greenness” of chemical reactions and synthesis plans. Previously described radial pentagon green metrics based solely on material efficiency are extended to include BI which takes into account the following potentials for environmental harm: acidification–basification (ABP), ozone depletion (ODP), global warming (GWP), smog formation (SFP), inhalation toxicity (INHTP), ingestion toxicity (INGTP), inhalation carcinogenicity (INHCP), ingestion carcinogenicity (INGCP), bioconcentration (BCP), abiotic resource depletion (ARDP), cancer potency (CPP), persistence (PER), and endocrine disruption (EDP). As with other material efficiency metrics, the benign index is defined as a fraction between 0 and 1 so that it may be added as another radial axis to produce an overall radial hexagon diagram that can be used to evaluate the “green” merits of any given chemical reaction. The utility of the method is demonstrated for industrial chemical reactions producing diphenyl carbonate (DPC) and phenyl isocyanate (PI) using both phosgene-based and nonphosgene-based chemistries, and for synthesis plans for the industrial production of aniline, phenol, and aspirin. A critical discussion is presented on the limitations of the method with respect to proper decision making in route selection, particularly the availability and reliability of key parameters, and the importance of obtaining experimental data for key parameters rather than relying solely on computational methods.