Atom Economy
Green Chemistry Institute Atom Economy Page 1 American Chemical Society ---------------------------------------------------------------------------------------------------------------------
CLEANING UP WITH ATOM ECONOMY
By Kathryn E. Parent, k_parent@acs.org
Introduction
Cleaning up the environment and, more importantly, preventing pollution are important issues in today’s world. The theme for the 2002 National Chemistry Week is “Chemistry Keeps Us Clean.” While the chemical industry is traditionally viewed more as a cause than a solution to pollution, chemistry does offer unique solutions in the area of waste prevention. One of the most fundamental of these solutions is the application of the green chemistry principle of atom economy to chemical reactions. Atom economy moves the practice of minimizing waste to the molecular level. Traditionally, chemists have focused on maximizing yield, minimizing the number of steps or synthesizing a completely unique chemical. Green chemistry and atom economy introduce a new goal into reaction chemistry: designing reactions so that the atoms present in the starting materials end up in the product rather than in the wastestream. This concept provides a framework for evaluating different chemistries, and an ideal to strive for in new reaction chemistry (1,2,3).
Green Chemistry Principle: Atom Economy
Atom economy means maximizing the incorporation of material from the starting materials or reagents into the final product. It is essentially pollution prevention at the molecular level. For example, a chemist practicing atom economy would choose to synthesize a needed product by putting together basic building blocks, rather than by breaking down a much larger starting material and discarding most of it as waste. Atom economy is an important development beyond the traditionally taught concept of percent yield. Barry Trost, from Stanford University, published the concept of atom economy in Science in 1991 (4). In 1998 he
CLEANING UP WITH ATOM ECONOMY
By Kathryn E. Parent, k_parent@acs.org
Introduction
Cleaning up the environment and, more importantly, preventing pollution are important issues in today’s world. The theme for the 2002 National Chemistry Week is “Chemistry Keeps Us Clean.” While the chemical industry is traditionally viewed more as a cause than a solution to pollution, chemistry does offer unique solutions in the area of waste prevention. One of the most fundamental of these solutions is the application of the green chemistry principle of atom economy to chemical reactions. Atom economy moves the practice of minimizing waste to the molecular level. Traditionally, chemists have focused on maximizing yield, minimizing the number of steps or synthesizing a completely unique chemical. Green chemistry and atom economy introduce a new goal into reaction chemistry: designing reactions so that the atoms present in the starting materials end up in the product rather than in the wastestream. This concept provides a framework for evaluating different chemistries, and an ideal to strive for in new reaction chemistry (1,2,3).
Green Chemistry Principle: Atom Economy
Atom economy means maximizing the incorporation of material from the starting materials or reagents into the final product. It is essentially pollution prevention at the molecular level. For example, a chemist practicing atom economy would choose to synthesize a needed product by putting together basic building blocks, rather than by breaking down a much larger starting material and discarding most of it as waste. Atom economy is an important development beyond the traditionally taught concept of percent yield. Barry Trost, from Stanford University, published the concept of atom economy in Science in 1991 (4). In 1998 he
References: (1) Anastas, P. T,; Warner, J. C. Green Chemistry: Theory and Practice, Oxford University Press: Oxford, UK, 1998. (2) Cann, M. C.; Connelly, M. E. Real World Cases in Green Chemistry, American Chemical Society: Washington, DC, 2000. See also the University of Scranton’s Greening Across the Curriculum Web Site, http://academic.scranton.edu/faculty/CANNM1/organicmodule.html (3) Ryan, M. A.; Tinnesand, M., Eds. Introduction to Green Chemistry, Washington, DC: American Chemical Society, 2002. (4) Trost, B. M. Science 1991, 254, 1471-1477. (5) The Presidential Green Chemistry Challenge is an award program sponsored jointly by the Environmental Protection Agency (Office of Pollution Prevention and Toxics) and the American Chemical Society—Green Chemistry Institute. Introduced in 1995, it is the only program to provide national recognition for green chemistry. The program offers five awards to academic researchers, industry, and government laboratories for innovations in the following categories: 1) academic, 2) small business, 3) alternative reaction conditions, 4) alternative synthesis, and 5) design of safer chemicals. For information about the Presidential Green Chemistry Challenge, refer to the Web Site: http://www.epa.gov/greenchemistry/presgcc.html (6) Trost, B. M. In The Presidential Green Chemistry Challenge Awards Program: Summary of the 1998 Award Entries and Recipients; EPA744-R-98-001, U.S. Environmental Protection Agency, Office of Pollution Prevention and Toxics: Washington, DC, 1998; p 2. (7) Trost, B. M. Acc. Chem. Res. 2002, 35, 695-705. (8) For a powerpoint presentation of atom efficiency, with excellent examples, see the Green Chemistry Network Web Site, http://www.chemsoc.org/pdf/gcn/atomeff.ppt (9) Witzel, J. Eric. J. Chem. Educ. 2002, 79, 352A-352B. (10) Trost, B. M. Acc. Chem. Res. 2002, 35, 695-705.