Green Chemistry - chemical ecology

Whole Earth, Winter, 1999 by Bradley Pine

DuPont chemists, for instance, developed a process that uses methyl isocyanate (MIC) as an intermediate for developing pesticides. Probably the most notorious chemical disaster in the 20th century involved the tragic death of thousands of people when MIC was accidently released at the Union Carbide facility in Bhopal, India. A safer production process that DuPont developed uses a catalytic approach that allows the generation of just the right amount of MIC [at just the right time] needed for conversion. As a result, MIC, which is very hazardous, does not need to be stored for the process, and potentially lethal spills or leaks are avoided. The process itself is safer and more atomically efficient, and the "in situ--just in time" approach reduced storage and liability costs for the manufacturer.

The benefits of green chemistry approaches are obvious.... The final hurdle to fully accepting that green chemistry principles will be the guidelines, indeed the impetus, for scientists engaged in the discipline of chemistry is the education of the next generation of chemists.

Twelve Principles of Green Chemistry

1. PREVENTION

It is better to prevent waste than to treat it or clean it up after it has been created.

2. ATOM ECONOMY

Synthetic chemistry should be designed to maximize the incorporation of all materials used in the process into the final product.

3. LESS HAZARDOUS CHEMICAL SYNTHESES

Wherever practicable, synthetic chemistry should use and generate substances that possess little or no toxicity to human health and the environment.

4. DESIGNING SAFER CHEMICALS

Chemical products should be designed to effect their desired function while minimizing their toxicity.

5. SAFER SOLVENTS AND AUXILIARIES

Wherever possible, auxiliary substances (e.g., solvents, separation agents, etc.) should be made unnecessary and innocuous.

6. DESIGN FOR ENERGY EFFICIENCY

Energy requirements should be minimized. If possible, synthetic chemistry should be conducted at ambient temperature and pressure.

7. USE OF RENEWABLE FEEDSTOCKS

Whenever technically and economically practicable, raw materials or feedstocks should be renewable, rather than depleting.

8. REDUCE DERIVATIVES

Unnecessary derivatization (use of blocking groups, protection/deprotection, temporary modification of physical/chemical processes) should be minimized or avoided, because such steps require additional reagents and can generate waste.

9. CATALYSIS

Catalytic reagents (molecules that help construct others but do not change themselves) should be as selective as possible. They are superior to stoichiometric chemistry, in which each molecule of reagent that is used is consumed.

10. DESIGN FOR DEGRADATION

Chemical products should be designed so that at the end of their function they break down into innocuous degradation products and do not persist in the environment.

11. REAL-TIME ANALYSIS FOR POLLUTION PREVENTION

Analytical methodologies need to be further developed to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances.