Introduction
Esterification reactions refer to those processes between carboxylic acids and alcohols reacting together to produce esters (Smith, 2011). Ethyl ethanoate also referred to as ethyl acetate is one of the esters and is prepared through a reversible reaction between an alcohol and an acid. The process results in the production of an ester and water. The catalyst used in the reaction is sulfuric acid, which also works to remove water that is produced and thus to increase the yield of ester produced. The preparation of esters through this method is a good introduction of how equilibrium manipulation may help in increasing yield from a given reaction (Renshaw & Lister, 2004). The procedure uses techniques such as distillation, heating, cooling and drying (Tindale, 1998).
The reaction process may be summarized using the following equation:
This experiment, therefore, aimed to synthesize ethyl ethanoate from ethanol as the alcohol and ethanoic acid as the carboxylic acid.
Experimental
Reflux apparatus was set up accordingly, and water turned on to a moderate flow before adding any of the reagents. First, 15 mL of ethanol was slowly poured down the top of the reflux condenser followed by 15 mL of glacial acetic acid, and finally mL of concentrated sulfuric acid. Heating was done under reflux for 20 minutes and the reaction content allowed to cool down by turning the heater off. The reaction content was added into a separating funnel. A round bottom flask was rinsed with a small amount of acetone and allowed to dry on a rack for the distillation.
In the fume hood, 10 mL of concentrated solution of bench reagent sodium carbonate was added. The separating funnel was separated releasing the pressure. Washing was done, and the reaction shaken until no more pressure could be released. The separating funnel was clamped at the bench allowing the layers to separate. The lower aqueous layer was run off carefully and discarded immediately in the sink with plenty of cold water. To the ethyl acetate in the funnel, 10 mL of water was added and shook vigorously in the fume hood. The content was allowed to separate, and the aqueous layer allowed to run off. Similarly, washing was done with 10 mL of saturated calcium chloride solution, and the separation of the mixture allowed. The lower aqueous layer was run off as completely as possible.
Ethyl ethanoate was run into a small conical flask and a few lumps of anhydrous sodium sulfate added. The flask was closed using a stopper and shaken vigorously. The content was given one minute to dry and decanted into a round-bottomed flask. The distillation apparatus was assembled on a dry round-bottomed flask, and an empty sample vial with lid weighed. Collection of distillate was done in the boiling range of 74-79OC to give pure ethyl ethanoate. The vial was capped and weighed to determine the weight of ethyl ethanoate.
Results
The experimental results obtained were as shown in Table 1 below. The initial temperature of the distillate was 74OC and increased up to 110OC. The maximum temperature was higher than the one in the literature. This difference may have resulted from impurities in the solvents, which may have increased the boiling point of the distillate.
The recorded initial temperature of the distillate was close to the temperature cited in the literature, 77.11°C (Louisiana State University, 2013).
Theoretical mass of the product may be calculated using the following procedure:
Mass of the reactants can be calculated using the formula;
Volume x densityMolecular mass = moles
Moles of Ethanol=15mL×0.789g/ml46.07g/mol
=0.257 moles
Moles of Ethanoic acid=15mL×1.05g/ml60.05g/mol
=0.262 moles
Mass=Moles×Molecular mass
=0.257 moles×88.11 gmol-1
=22.64 g
The percentage yield for ethyl acetate was calculated as follows:
% Yield=Practical YieldTheoretical Yield ×100
=8.2822.64×100
=36.57%
The produced ethyl acetate had a percentage yield of 36.57%. The yield obtained was very far from attained the 100% mark. This reduction in percent yield may have resulted from the evaporation of the working reagent in the process of doing an experiment, loss of reagent during washing or other experimental errors. To increase the percent yield, care should be taken to avoid solvent evaporation or loss of solvent when running off the washing solvents. The appearance of the product was a clear liquid just as expected (Louisiana State University, 2013).
In conclusion, the experiment successfully facilitated the synthesis of ethyl acetate and the determination of the percentage yield.
Reference List
Louisiana State University. (2013). Ethyl Acetate Solvent Properties. Retrieved October 5, 2014, from http://macro.lsu.edu/HowTo/solvents/ethylacetate.htm
Renshaw, J., & Lister, T. (2004). Essential A2 Chemistry for OCR. Oxford: Nelson Thornes.
Smith, M. B. (2011). Organic Chemistry: An Acid—Base Approach. London: CRC Press.
Tindale, A. (1998). Chemistry: a concise revision course for Cxc. Oxford: Nelson Thornes.
