Quantifying Environmental Impact Efficiency, -factors, and Atom Economy

Quantifying Environmental Impact Efficiency, E-factors, and Atom Economy 

Everyone agrees that green chemistry and green manufacture are good things. The websites and pamphlets of all the major chemical companies emphasize their concern for the environment. They all say that their processes and products are efficient, green, and environmentally friendly. But how should we compare these processes How should we judge such claims  

let us define some key terms. One method for quantifying a reaction s efficiency is by examining the reactant conversion, the product selectivity, and the product yield over time. The reactant conversion is the fraction of reactant molecules that have transformed to product molecules (regardless of which product it is). The selectivity to product P is the fraction (or percentage) of the converted reactant that has turned into this specific product P. The yield of P is simply conversion x selectivity. High conversions in short time spans mean smaller and safer reactors. Similarly, high selectivity means less waste, and simpler and cheaper separation units. Thus, conversion, selectivity, and yield are all measures of the reaction efficiency. 

The concept of atom economy, introduced by Barry Trost in 1991, is similar to that of the. E-factor [12]. Here one considers how many and which atoms of the reactants are incorporated into the products. With these two concepts, we can evaluate chemical reactions to get a quantitative result. 

However, examiningthe E-factor for this reaction, we see that for every three moles of benzophenone we produce one mole of chromium sulfate and six moles of water. The molecular weight of benzophenone is 182.2 gmoH1, so every kilogram of benzophenone contains 5.48 moles of benzophenone. This means that for every kilogram of benzophenone we generate 5.48/3 = 1.83 moles (or 0.717 kg) of 

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