1. Exp. 13: CALCULATION, CHROMATOGRAPHIC, AND SPECTRAL APPLICATIONS

2. Objectives:  To review common laboratory calculations.  To learn green chemistry calculations.  To review how to use the calculated values to reach conclusions.

3. LIMITING REAGENT  Must convert the amount of each reagent to moles first using their molecular weights.  Next, take into account the stoichiometric ratio of the reactants and products. This should leave you in the units of MOLES OF PRODUCT.  Finally compare the moles of product produced by each reagent. The reagent that produces the least moles of product is your limiting reagent.

4. THEORETICAL YIELD  Theoretical yield is always in GRAMS OF PRODUCT.  Based on the limiting reagent, convert the moles of product to grams of product using the MW of the product.

5. PERCENT YIELD  Percent yield is the actual weight of the product that you made over the theoretical amount of product that you calculated X 100.

6. GREEN CHEMISTRY CALCULATIONS  Green chemistry calculations are used to determine how “environmentally friendly” your choice of reagents, solvents, and conditions were.  This includes ATOM ECONOMY, EXPERIMENTAL ATOM ECONOMY, AND “E” PRODUCT.

7. ATOM ECONOMY  Atom economy is based on the efficiency of reactant atoms converted to product atoms.  Any atoms of the reactants that did NOT appear in the product structure were converted to side products or waste, which has to be disposed of. Sometimes the side products and waste generated is harmful to the environment.  For this reason, an experiment should be designed to minimize the generation of waste and unnecessary side products.

8. ATOM ECONOMY Atom economy = MW desired product * 100  MW reactants Atom economy is based on which reactants were selected to make the product. It assumes that the reactants were used in equivalent amounts, meaning that no excesses of any reactant were used. The closer the atom economy is to 100%, the better!

9. EXPERIMENTAL ATOM ECONOMY Experimental atom economy = theoretical yield of product (g) * 100  mass reactants Sometimes an excess of one reactant is used in order to drive the reaction to completion. For this reason, the experimental atom economy is calculated. Experimental atom economy is a more precise measure of efficiency than the atom economy, since it takes into account the mass of each reactant used.

10. “E” PRODUCT “E product” = (% chemical yield * % experimental atom economy) 100 “E” product is the ultimate measure of efficiency, since both the condition used and the amount of product that resulted under those conditions is taken into account. “E” product is a number, not a percentage! The higher “E” product is, the better!

11. COST ANALYSIS  Cost per synthesis: total the cost of all reactants, solvents, and catalysts used to perform the synthesis.  Cost per gram: divide the cost per synthesis by the actual weight of product in grams.