Green Chemistry Labs: Taking a Microscale Approach

As the pressure to "go green" has many modern companies changing their manufacturing processes to greener methods, college universities are also jumping on the green train. More specifically, many university chemistry programs are recognizing the errors in the old way of performing chemistry laboratory experiments; professors have realized that there is no reason to teach their pupils the merits of green chemistry without employing such practices in their laboratories as well. With practices such as "safer solvents and auxiliaries," "catalysis," "atom economy," and "prevention (of excess or hazardous waste)," among the twelve universally recognized principles of green chemistry (as recorded by the Environmental Protection Agency), universities are trying to shift their chemistry lab practices to reflect such principles.

Among the most popular ways to take a greener approach to chemistry labs is that of the "micro scale" approach. Publishing companies have produced micro scale approach chemistry lab textbooks/manuals; perhaps among the most popular of these are some of the organic chemistry micro scale lab manuals, as implementing a more micro scale approach to organic chemistry experiments is considerably more easy to do than with some other chemistry courses (such as Quantitative Analysis for Chemistry, which often deals with large scale titrations). This micro scale approach allows its users to perform all of the basic organic chemistry experiments, just on a much smaller scale (i.e. with far less reactants used). Because of this, students must take extra precautions to avoid any and all contamination of reactants before use; the smaller amounts of reactants used (often mere milligrams of a chemical compound) mean that even a very small amount of a contaminating substance can greatly affect the entire reaction. Additionally, students should learn to expect very small weights of final products for most reactions. Since almost no chemical reaction proceeds 100% to completion, a small amount of reactants will mean an even smaller amount of products. It then becomes absolutely crucial for students to take extra care in ensuring that all of the products of a reaction are completely transferred to the next piece of glassware needed in the experiment. Any loss of product (or reactants) will lead to an even more incredibly minute amount of final products in a micro scale laboratory experiment.

Additionally, some organic chemistry labs are attempting to utilize the principle of "safer solvents and auxiliaries" which simply means using non-hazardous solvents when appropriate and eliminating the use of unnecessary solvents altogether in other reactions. While many chemistry experiments use solvents to aid with the relative speed of a reaction, green chemistry labs often instruct students to forego the solvents altogether and instead physically grind the reactants together with a mortar and pestle in order to initiate the reaction of the reactant chemicals. This process obviously takes much more time that a traditional solvent-based reaction might. One such experiment that is being used in organic chemistry labs today to teach the possibilities of such solvent-free green chemistry is that of the solvent-free Wittig Reaction between reactants such as benzyltriphenylphosphonium chloride, 4-bromobenzaldehyde and potassium phosphate.

Sources Consulted:

Environmental Protection Agency (EPA, http://www.epa.gov/greenchemistry/)

Introduction to Organic Laboratory Techniques: A Microscale Approach (by: Pavia, Lampman, Kriz)