Atom-economy factor

Anthraquinone is widely use in the manufacture of a range of dyes. Two possible routes for manufacturing anthraquinone are (1) from the reaction of 1,4-naphthoquinone with butadiene and (2) reaction of benzene with phthalic anhydride. Describe mechanisms for both these reactions and identify likely reaction conditions and any other reagents required. Compare the atom economy of the two routes. Identify three factors for each route that may influence the commercial viability. 

In Chapter 1 the concept of atom economy was discussed as a design tool. Similarly in Chapter 2 the term E-factor was introduced as a measure of the amount of by-products formed per unit weight of product. Unlike atom economy the E-factor is determined from an actual process or can be extrapolated from laboratory work. As a valuable extension to the E-factor concept Sheldon has proposed an Environmental Quotient which is the product of the E-factor and a by-product unfriendliness ... 

The atom economy for this process is 86.5% (100 X 116/134), which is reasonable. To calculate the E-factor and EMY further information is needed. From published literature (Vogel s Practical Organic Chemistry ), a standard procedure is to mix butanol (37 g) with glacial acetic acid (60 g), and a small amount of sulfuric acid catalyst (ignored in all calculations). Following completion of the reaction the mixture is added to water (250 g). The crude ester is washed further with water (100 g), then saturated sodium bicarbonate solution (25 g) and finally water (25 g). After drying over 5 g of anhydrous sodium sulfate the crude ester is distilled to give product (40 g) in a yield of 69%. 

Review a recent synthetic reaction you have carried out in the laboratory. Write a balanced equation for the reaction(s) and calculate the atom economy. From your experimental results calculate the Yield, E-factor and Effective Mass Yield (ignoring any water used). Identify ways in which this reaction could be made greener. 

Histograms tracking the individual and cumulative performances of reactions maybe easily constructed according to reaction yield, atom economy, stoichiometric factor. 

Mass balancing unifies all metrics such as yield, atom economy, TON, TOF, and so on. Therefore, the application of mass indices and environmental factors presents itself as an integrating solution with moderate data demands. A fair comparison of alternative... 

There are some ways to evaluate environmental burden in chemical synthetic processes. The atom economy is the fraction of the atoms in the product to the fraction of all atoms in the reactants. The E factor is the ratio of the mass of all waste to the mass of product. For the following reaction concerning the production of propylene oxide, calculate the theoretical atom economy and E factor. 

Iu search for efficieut aud greeuer processes over the past few years various heterogeneous catalysts such as titanium incorporated mesoporous molecular sieves [45,46], Schiff-base complexes supported on zeolite [47] and Zn(II)-Al(III) layered double hydroxide (LDH) [48], oxomolybdenum(VI) complexes supported on MCM-41 and MCM-48 [49], polyoxometallate supported materials [50], Co and Mn-AlPO s [51] etc. have been developed and studied for the catalytic epoxidatiou of a-pinene. Many of these processes suffer from drawbacks and limited applicability due to the poor conversion and also the selectivities. Sacrificial aldehydes are often used as an oxygen acceptor in such processes to achieve reasonable yield and selectivities but, this procedure leads to an increase in the E-factors and decrease in the atom economy [51]. 

While the concept of atom economy is simple, unlike the E factor it does not take into account the actual yield or stoichiometry (actual masses or molar excesses)... 

The entire process is catalytic the only by-product is water. More than 80% of the process solvent (toluene) can be recovered. The efficiency of amide bond formation is thus hindered by the widespread use of reagents with poor atom economy. The development of reagents with lower mass intensity (MI) factors or catalytic methods such as the exciting application of boric acid or its derivatives to catalyze amide formation in an eco-friendly manner would certainly transform the environmental profile of many processes. 

Atom economy is strictly a theoretical number. The calculation considers only reagents from the balanced chemical reaction. The calculation does not include practical factors such as yield or excess reagents. A given reaction has the same atom economy whether its yield is 90% or 10%. Regardless, atom economy was the first accepted attempt at quantifying the greenness of a reaction. 

Shortly after Trost introduced the idea of atom economy, Roger Sheldon of Delft University of Technology in the Netherlands reported another green metric called E-factor.30 31 E-Factor is the ratio of the mass of the total waste from a process to the mass of the product generated in that same process (Equation 13.5). 

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

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. 

As an example, let us consider the stoichiometric oxidation of diphenylmethanol to benzophenone, one of the most commonly used photosensitizers in photochemistry (Figure 1.3). We will evaluate this reaction using the measures of product yield, product selectivity, E-factor, and atom economy. In this reaction, three equivalents of diphenylmethanol react with two equivalents of chromium trioxide and three equivalents of sulfuric acid, giving three equivalents of benzophenone. First, let us see how the reaction measures with respect to product yield and selectivity. Assume that this is an ideal chemical reaction which goes to completion, so one obtains 100% yield of the product, benzophenone. If no other (organic) by-product is obtained, the product selectivity is also 100%. This is all well and good, and indeed for many years this has been the way that chemical processes were evaluated, both in academia and in the (fine-) chemical industry. 

Some processes and products seem more eco-friendly than others. Often this is because we see only part of the process. An overall environmental impact analysis should take into account not only the chemical reactions, but also the hazards and consequences of acquiring and transporting the raw materials. Additionally, it should factor in the overall energy demand. A reaction can have 100% atom economy, yet still be problematic because of hazardous reagents. Adding Br2, HF, or HCN to a double bond, for example, is clean from the atom economy perspective, but storing... 

Examine the list of the 12 principles of green chemistry shown at the beginning of this chapter. Which of these principles relate to the concepts of atom economy, the E-factor, and the environmental quotient Q ... 

The environmental and economical benefits of one-pot catalytic fine chemical syntheses, in which various successive chemical steps are accomplished in the same reaction vessel, generally over a bifunctional (or multifunctional) catalyst, are obvious. The reduction in the number of synthetic and separation steps has various positive consequences environmentally more sustainable processes (higher atom economy and lower environmental factors), lower operating costs, lower production of wastes and in general an improvement in the safety conditions.[1 31 The environmental advantages are still more remarkable when the transformation of renewable raw materials, such as mixtures of natural terpenes or carbohydrates are concerned. 

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