Ester Practical Essay, Research Paper
AIM To prepare and purify an ester.
MATERIALS
Quickfit set
2 clamps and bossheads
250mL beaker
ethanol
concentrated sulphuric acid
25mL measuring cylinder
distilled water
sample of nail polish (for smell comparison)
1retort stand
matches
marble chips
glacial acetic acid
separating funnel and stopper
1 mol L-1 sodium carbonate solution
METHOD
RESULTS
After carefully assembling the apparatus and given a safety approval by the
teacher, I carefully added the ethanol and glacial acetic acid into the pear shaped flask. A few marble chips were added to avoid the larger reactive bursts of the mixture during refluxing that were predicted. The condenser was then securely placed on top of the flask, clamped in place, and connected to the water supply. The concentrated sulfuric acid was gathered in a test tube, and eight drops were released well inside the condenser, on the walls. The teacher again committed to safety checks before lighting the Bunsen burner under the flask. After it had been lit, it was refluxed carefully, allowing the condensation ring to rise about a half of the way up the condenser, this reoccurred for half an hour. After the somewhat clear mixture had cooled for about 5 minutes, it was placed in a separating funnel with 20mL of water. Once shaken, it was left until a small organic layer was visible at the top, and most of the water was discarded. This washing procedure of the organic layer was repeated with sodium carbonate solution (about 20mL), and most of this was discarded. The 250mL beaker was filled with about 150mL of water, and a thin, glassy layer, the ester, was visible on top. There was a strong smell emulating from the solution, of nail polish remover, wafting was not necessary. This smell was compared to that of commercial nail polish remover, and a slightly stronger smell was noted.
DISCUSSIONThe relevance of esters strands from the production of such hydrocarbons nowadays imitating those esters that occur naturally, such as sweet fragrances, and fats and vegetables oils. In determining the properties of esters, and producing them, we are able to produce them with more ease.
Esters contain the functional group -COO-, and have similar structures to carboxylic acids, except the Hydrogen of the carboxyl group in the acid is replaced by an alkyl group in the ester. Basically, esters are regarded as two alkyl groups linked by an ester group.
The R?s represent the alkyl groups
R ? C = Oand the circled area is the Ester?s
O ? R?functional group.
Esters are naturally occurring in fragrances of flowers and fruits (short chain esters), and animal fats and vegetable oils (long chain triesters).
Esters have low boiling points and are less soluble in water than their corresponding carboxylic acids because of their inability to form Hydrogen bonds.
An Ester is prepared by reacting an alcohol with a carboxylic acid in the presence of concentrated sulfuric acid (catalyst), through refluxing the solution. The reaction is slow and often extended heating is required to achieve a satisfactory quantity of Ester in a reasonable time with water.
R ? C = O + R? OH R ? C = O + H2O
O conc. O ? R?
H2SO4
The carboxylic acid loses a hydroxyl group and the alcohol loses a proton. A molecule of water is eliminated between the reactants for every molecule of ester formed. When a small molecule such as water is eliminated in this fashion, the reaction is known as condensation. Therefore an ester will be produced if either excess alcohol or excess carboxylic acid is used, or water is removed as it forms.
Reflux is appropriate as water will evaporate easier than the ester, as established before, and the pure ester will be left in the flask. Any impurities will be discarded by the washing procedure, as the ester (organic layer) will be at the top of the flask, and the water and the sodium carbonate solution will be at the bottom and discarded through the funnel.
CONCLUSION The ester, by comparison to the nail polish remover, was prepared and purified
successfully. However, the ester, being only produced on smaller scale could not be isolated, only judging by the smell of the substance.
nuthing mudcrab.