Presentation on theme: "Exp. 13: CALCULATION, CHROMATOGRAPHIC, AND SPECTRAL APPLICATIONS."— Presentation transcript:
Exp. 13: CALCULATION, CHROMATOGRAPHIC, AND SPECTRAL APPLICATIONS
Objectives: To review common laboratory calculations. To learn green chemistry calculations. To review how to use the calculated values to reach conclusions.
LIMITING REAGENT & THEORETICAL YIELD Mass RCT Moles RCT (using MW rct ) Moles RCT Moles PROD (using stoichiometry) Moles PROD Mass PROD (using MW prod ) Determine limiting reagent. Theoretical yield is always in the units of GRAMS of PRODUCT!
PERCENT YIELD Percent yield = ACTUAL PRODUCT MASS (g) X 100 THEORETICAL YIELD (g)
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 ”.
ATOM ECONOMY Atom economy is based on the efficiency of reactant atoms converted to product atoms. Q: Were ALL of the 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. 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.
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!
EXPERIMENTAL ATOM ECONOMY Experimental atom economy = theoretical yield of product (g) * 100 mass reactants Q: Did we use only the amount necessary to generate the product? 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.
“E” PRODUCT “E product ” = (% yield X % experimental atom economy) 100 “E product ” is the ultimate measure of efficiency, since both the conditions 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!
IMPROVING EFFICIENCY… An efficient reaction would have 100% Atom Economy and 100% Experimental Atom Economy. One could improve the efficiency of a reaction by adjusting the conditions of a reaction in an effort to improve either of these values, such as: Use different reactants to form the product (AE) Use different amounts of reactants to form the product (EAE).
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.
HPLC and TLC Chromatography Introduced in Experiments 4 and 5. Difference between ANALYTE POLARITY and SOLVENT POLARITY. UV detector is used in both. In order to be detected, compounds must be UV active. Most solvents used in TLC and HPLC are not UV active, therefore do not appear on the TLC plate or in the HPLC chromatogram!
IR SPECTROSCOPY Introduced in Experiment 10. Base values are given in correlation tables. Actual values are reported from actual spectrum Don’t ever mention sp 3 CH when using IR spectroscopy to differentiate between reactants and products! They are too common!
MELTING POINT ANALYSIS Introduced in Experiment 7. Detects all impurities! Recorded as T i -T f range. Pure = matches literature mp EXACTLY! Impure = lower T i, higher T!