Green atom efficiency/economy

What is green chemistry (5) What is atom economy (6) How can atom efficiency be applied (7)... 

Atom efficiency the percentage yield (molar flow of the desired product divided by the molar flow of the limiting reactant, taking into account the stoichiometry of the reaction) multiplied by the atom economy. It could be used to replace yield and A E. Eor example, AE could be 100% and yield 5%, making this a not very green reaction. 

The atom economy is an important concept of the green chemistry philosophy proposed by Trost (3). This concept is that reactions should be designed to be atom efficient for economic and environmental reasons. Therefore, as many of the atoms in the reactants as possible should be included in the products. For evaluation of the concept of atom economy, it is necessary to consider atom efficiency. The atom efficiency of a reaction is defined as the ratio of the molecular weight of the desired product to the sum of the molecular weights of all of the materials produced in the process. For example, in the reaction that converts... 

Green chemistry has introduced several new terms and new research frontiers, including "eco-efficiency," "sustainable chemistry," "atom efficiency or economy," "process intensification and integration," "inherent safety," "product life-cycle analysis," "ionic liquids," "alternate feedstock," and "renewable energy sources."... 

As much as it is a key in achieving economic objectives, catalysis is also a powerful tool in realizing the goals of green chemistry. Innovation in the field of catalysis is driven by both profit motives and efforts to make more eco-efficient processes. Most often profits are markedly improved with the development of green processes. An important concept of green chemistry that can be addressed by the use of catalysis is atom-efficiency, also known as atom-economy. 

An important aspect of green chemistry involves atom economy. If we consider the oxidation of PhCH(OH)CHj to PhC(=0)CH3 using chromium trioxide, the atom efficiency, the proportion of the product that is actually something we want, is 42 % (Equations 25.4 and 25.5). If the oxidation could be done using molecular oxygen as the oxidant and a catalyst, then this rises to 86 % (Equations 25.6 and 25.7). In both cases, this is only a theoretical figure to get a more practical... 

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. 

Measurements of the chemistry and process efficiency are attempts to address Green Chemistry Principles 2 (atom economy) and 8 (reduce derivatives). Atom economy is one of the most widely known measures of chemistry efficiency [43-45] and is calculated from... 

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. 

The teaching was divided in basic themes i.e Atom economy. Industrial Processes, Alternative Solvents, New Feedstocks and Products, New Reactions and New Synthetic Methods. In addition topics related to current research in Green Chemistry were addressed with the aim to familiarize the students with the strategies behind the planning and designing of efficient and "greener synthetic routes. 

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,... 

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