Extraction of Eugenol

Introduction

One of the most widely distributed class of compounds known to nature, are that of the esters. In fact the distinct flavors and aromas of many fruits and their flowers are the result of this functional group, or a combination of compounds with this functional group. Because of the distinctive aromatic properties of the esters, they make an excellent choice for the additive flavors in many commercial food and beverage products (Amirhossein et. al, 2014) The ester linkage is also present in animal fats and in many biologically important molecules (Fischer, Craig, 2001).

Esters can be synthesized in the lab through a process called esterification, which refers to the reaction of an alcohol and a carboxylic acid under reflux conditions with the addition of an acid catalyst (Fischer, Craig 2001). In the present experiment, isopentyl acetate commonly referred to as banana oil for its comparable scent to the fruit, is synthesized via this process of esterification. Fig.1 denotes the standard reaction for the production of isopentyl acetate by reacting acetic acid with isopentyl alcohol. The mechanism proceeds

Figure 1: Reaction of Acetic Acid and Isopentyl Alcohol to Produce Isopentyl Acetate. (www.dbooth.net)

by way of nucleophilic substitution at the acyl-carbon of the carboxylic acid, in the presence of a strong acid catalyst, in this case sulfuric acid. The mechanism involves a series of steps including protonation, nucleophilic attack, proton transfer, dehydration, and finally dehydrogenation. Each step of the mechanism is reversible and therefore the reaction reaches an equilibrium that leans heavily in favor of the reactants. In order to create a sufficient amount of product, an excess of acetic acid must be used, as it is more easily removed from the reaction mixture through extraction using sodium bicarbonate and water. Finally, the ester must be further purified following drying using anhydrous sodium sulfate, by simple distillation. The product can then be weighed, and percentage recovery can be determined.

Materials and Methods

Figure2: Standard Reflux Apparatus (www.chem.wisc.edu)

To begin the procedure, a standard reflux apparatus was constructed similar to that shown in Figure 2, using a 100-mL round bottom flask and a water cooled condenser. Using a pre-weighed graduated cylinder, approximately 5.0-ml of isopentyl alcohol (Fisher Scientific Lot 062331, acidity .001%) was weighed and measured, at 4.16 grams, and transferred to the reflux round bottom flask. Then, using the same unwashed graduated cylinder, approximately 7.0-mL of acetic acid (Fisher Scientific Lot 131692, assay 99.9%) was added to the reflux flask. The graduated cylinder was kept unwashed as to ensure the transfer of as much isopentyl-alcohol as possible. Finally, to complete the mixture, approximately 1-mL of concentrated sulfuric acid (Fisher Scietific Lot 114473, assay 96.7%) was added to the reflux flask using a calibrated Pasteur pipet. This was then immediately mixed by swirling as to ensure full exposure of the acid catalyst to the carboxylic acid for protontion. Lastly, a corundum boiling stone (Chemware PTFE Lot 11402) was added to the mixture and the flask was reconnected to the apparatus. A carborundum boiling stone, made of Teflon was chosen because it can withstand the acidity of the mixture, unlike other materials such as calcium carbonate which readily dissolves in the acidic liquid. Once all of the components were mixed, the mixture was brought to a boil using a heating mantle, and water was allowed to circulate through the condenser as to undergo the reflux procedure for an hour's time. The purpose of this procedure is to form products without losing the components of the reaction mixture. This accomplished by bringing the reaction mixture to its boiling point, causing a greater number of molecular interactions and thus forming products. The compounds of the reaction flask are not lost to evaporation because a cool water condenser is placed vertically above the boiling flask which cools the volatile vapors, condensing them back into the reaction flask (Pavia, et al.,2007).

After an hour of reflux, the apparatus was disassembled,