Atomic economy

Atomic Economy and Chemical Conversions

The atom economy (also atom efficiency ) is in terms of mass percentage of a chemical reaction of the starting materials in the products transferred atoms. The term was defined by Barry M. Trost in 1991 .

Importance and application

A practicable method has been described for determining the atom economy of multi-stage syntheses.

In the chemical industry, the atomic economy is playing an increasingly important role. Modern syntheses are designed in such a way that they proceed with high atom efficiency, which is almost always the most economical process. As a result, the disposal of undesired by-products, which often arise in stoichiometric amounts, is minimized or even completely superfluous.

Large chemical companies, e.g. B. BASF AG (keyword: Verbundstandort ), have been successfully practicing applied atom economy on a large scale for decades. Not only the maximum efficiency of a production process is considered, but also the efficiency of a complex location as a unit. Alleged waste materials from production process A can represent valuable starting materials for production process B.

This concept is also pursued from an energetic point of view. The (exothermic) reaction energy released during continuous processes can be used as heating energy in other areas of the plant.

Systematic approaches to a “sustainable” chemistry and the inclusion of other factors that go beyond atomic economy are described in the literature. This involves the use of renewable raw materials , the inclusion of life cycle assessments , social assessments , product life cycles , etc.

Examples

• A completely atom-efficient reaction is the [4 + 2] cycloaddition (Diels-Alder reaction), in which all atoms of the starting materials can be found in the product, as well as the related Cope and Claisen rearrangements .
• The Fries shift takes place in an atom-efficient manner, there are no low-molecular waste materials.
• The Passerini reaction is an atom-efficient multicomponent reaction without any generation of low molecular weight waste.
• The addition of bromine to an alkene to form a dibromoalkane is an atom-efficient reaction; on the other hand, the catalytic bromination of benzene is less atom-efficient, since one equivalent of hydrogen bromide is formed in addition to bromobenzene , not to mention the whereabouts of the catalyst.
• The Ugi reaction is an atom-efficient multicomponent reaction in which only one equivalent of water is split off.
• The hydroformylation is an atom efficient reaction when the regioselectivity is high.
• In the industrial phenol synthesis using the cumene hydroperoxide process , acetone is obtained as a by-product in a stoichiometric amount; the atomic efficiency is mediocre.
• The Grignard reaction is a reaction that is not very atom-efficient and produces considerable salt waste.
• The production of thioamides from amides with Lawesson's reagent or phosphorus pentasulfide is not very atom- efficient, and the amounts of waste are usually considerable.
• The Gabriel synthesis is an example of a synthesis with markedly poor atom economy; even with high yields, much larger amounts of waste arise than from the desired product (primary amine ).
• In the case of a racemate resolution , an atom economy of 50% can at best be achieved, unless the undesired enantiomer racemizes continuously or it can be racemized externally and recycled.
• At best, the Cannizzaro reaction delivers the desired reduction product - an alcohol - with 50% atom economy - the remaining aldehyde is oxidized to the carboxylic acid.

The search for new light-induced multi - component reactions is the subject of current research. This shows new methods of organic synthetic chemistry , the need for sustainable and atom- and energy-efficient reactions is becoming more and more urgent.

literature

• Barry Trost : The atom economy - a search for synthetic efficiency , in: Science 1991 , 254 , pp. 1471-1477, doi : 10.1126 / science.1962206 .
• Manfred Schubert (editor): Low-waste and waste-free technology , VEB Deutscher Verlag für Grundstoffindindustrie, Leipzig, 1st edition, 1987, ISBN 3-342-00093-7 .

Individual evidence

1. ↑ Marco Eissen, Radoslaw Mazur, Heinz-Georg Quebbemann and Karl-Heinz Pennemann: Atom Economy and Yield of Synthesis Sequences , Helvetica Chimica Acta 87 ( 2004 ) 524-535. doi : 10.1002 / hlca.200490050 .
2. ↑ This is strictly forbidden for batch processes for security and quality reasons.
3. ^ (A) Marco Eissen, Jürgen O. Metzger: Environmental Performance Metrics for Daily Use in Synthetic Chemistry , Chemistry a European Journal 8 ( 2002 ), 3580-3585; (b) Marco Eissen, Jürgen O. Metzger, Eberhard Schmidt, Uwe Schneidewind : 10 Years After “Rio” - Concepts for the Contribution of Chemistry to Sustainable Development , Angewandte Chemie 114 ( 2002 ) 402–425.
4. ↑ ^{a b} Silvia Garbarino, Davide Ravelli, Stefano Protti and Andrea Basso: Photoinduced multicomponent reactions , Angewandte Chemie 128 (2016) pp. 15702–15711.