EXPERIMENT 7 ORGANIC SYNTHESIS: MICRowAVE-ASSISTED FISCHER ESTERIFICATION Materi

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EXPERIMENT 7 ORGANIC SYNTHESIS: MICRowAVE-ASSISTED FISCHER ESTERIFICATION Materials Needed isopentyl 1.0-2.0 mL of an alcohol to be chosen from the 3-methyl-1-butanol (isoamyl alcohol, following: alcohol), 1-octan (n-octyl alcohol), phenyimethanol (benzyl alcohol) 2.0 mL acetic acid 10 drops concentrated sulfuric acid 0.2 g silica beads saturated aqueous sodium chloride (sat NaCl(aq) 10% aqueous sodium bicarbonate (NaHcos(aq)) anhydrous sodium sulfate pellets (Nazso4(s) 10 mL diethyl ether 1 Glass Chem" pressure vessel and torque tool for tightening cap 1 very large test tube, several small test tubes, 1 screw-cap vial, Pasteur Pipettes Textbook Reading Assignment Smith, Chapter 13.6 INTRODUCTION A carboxylic acid and an alcohol react in the presence of a acid catalyst to form an ester and water as shown in equation 1. This reaction, termed Fischer esterification in honor of its discover can be used to prepare a variety of esters H (cat) R-C -OR' H20 HOR' R-C-OH water side product alcohol ester carboxylic acid The esterification reaction is reversible with an equilibrium constant that favors the products only slightly Therefore, in order to get a decent yield of the ester product, an excess of one of the reactants is usually used to drive the equilibrium to the right (Le Chatelier's Principle). In addition, a drying agent, such as silica beads can be used to absorb the water side product as it is formed and again drive the equilibrium toward the products rather slow (even at elevated temperatures with the acid catalyst added): too slow to However, this reaction i lab period using standard heating methods. Luckily, wsU recently purchased a allow us to carry it out in a 2-hou Microwave Assisted Reaction System (MARS) which wi allow us to use microwave heating to speed the process n this experiment you will choose one of the following three esters sopentyl acetate, benzyl acetate, n-octyl acetate and synthesize it by reacting acetic acid with the appropriate alcohol (3-methyl-1-butanol, benzy radiation at 130 eC for 15 minutes. Concentrated Haso will be used as a under microwave alcohol, or 1 octanol catalyst and silica beads added to absorb the water side product and drive the equilibrium need to carry out a several step procedure designed to isolate the este once the reaction period is over you wi product as a pure substance (free from any leftover starting materials. This is a typical, though relatively simple organic synthesis procedure. The weight of the product obtained (i.e. the yield) will be measured and the percent eld determined. The synthesized esters will also be assessed for their fragrance

Explanation / Answer

1) Acetic acid is a limiting reagent while alcohol can be used in different volumes as an excess reagent for reaction by increasing the volume of alcohol the conversion of reaction increases as it converts acetic acid to ester faster.

4) 100% yield is never achieved in any reaction as there are always unreacted reagents left in the reactants as well as you can not achieve 100% conversion in any reaction as some of the reactants remain unreacted

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