Synthesis of Esters

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Esters are a class of organic compounds with the general formula RCOOR’. Ester also contributes the flavor and aromas in fruits and flowers. The esterification reactions will use in the procedure, which are the interaction of a carboxylic acid with an alcohol, aided by an inorganic acid catalyst (H2SO4). Moreover, the green method will not use any catalyst but using heating source instead (microwave). Based on the comparison of two methods, green chemistry is the effective method because reduce the consumption energy and less time consuming than the non-green chemistry preparation. Introduction

 Esters are among the most widespread of all naturally occurring compounds. Many simple esters are pleasant-smelling liquids that are responsible for the fragrant odors of fruits and flowers. Examples are benzyl acetate, which is finding in orange oil, and isopentyl acetate, which is the part of banana oil. The ester linkage is also present in animal fats and in many biologically important molecules.       Esters can be formed from both organic and inorganic acids and the process of producing an ester is called an Esterification. Esters of organic acids are usually colorless, neutral liquids, pleasant-smelling and generally insoluble in water but readily soluble in organic solvents. Esters are prepared synthetically in large quantities for commercial use as artificial fruit essences and other flavorings and as components of perfumes. Esterification is used to derivatize carboxylic acids and other acidic functional groups. In a typical reaction, Esterification involves the condensation of the carboxyl group of an acid and the hydroxyl group of an alcohol, with the elimination of water (Konwar, 2008). Many Esterification reactions are slow and elevated temperatures are frequently used. Since the Esterification reaction is an equilibrium reaction, it may be necessary to remove the water generated during the reaction.       The chemical industry uses esters for a variety of purposes. Ethyl acetate, for example, is a common solvent found in nail-polish remover, and dialkyl phthalates are used as plasticizers to keep polymers from becoming brittle (Wilkes, 2005). They also have important medical uses. Ethyl nitrite is a diuretic and an antipyretic. The aim of this experiment is to compare the effectiveness between green and non-green chemistry of esterification by using the infrared spectroscopy and each percentage yield. Non-green chemistry will use acid catalyst in the reaction, but green chemistry will use microwave radiation instead of the acid-catalyst. The preparation of banana oil will perform in this experiment to determine the effectiveness of green and non-green chemistry. Below is the general mechanism of esterification:


Experiment Details
A. Non Green method of preparation of Banana Oil
 Isopentyl alcohol was used to synthesize the banana oil. 15-mL of isopentyl alcohol was placed in a 100-mL round-bottom flask and 20 mL of glacial acetic acid was added. Then, swirl the flask and 4 mL of conc. H2SO4 was added carefully to the flask. A reflux condenser was set up to reflux the mixture for one hour, and then cool down the mixture to room temperature. After the mixture was cooled down, the reaction mixture was placed in a separatory funnel followed by 55 mL of cold water to separate the lower aqueous layer. Then, extract the organic layer (upper layer) with 25 mL of 5% sodium bicarbonate solution twice and also extract the organic layer with 25 mL of water. Finally, add 5 mL of saturated aqueous sodium chloride to aid in layer separation which removes traces of water from the organic layer. Then, Draw off the lower aqueous layer and Pour the top organic layer into an Erlenmeyer flask and dry with 2 g of anhydrous magnesium sulfate.(UOregon) The distillation was performed after the substance dried.  Collect all distilled material but collect the...
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