Esters

Esters have many uses, especially in nature. Polyesters (long chains of esters) can be made synthetically to make fabrics, but also occur naturally in DNA. They are also present in fats and oils.

Hydroiodic Acid (Zeisels Alkoxyl Method)

Place about 0.1ml of the ester into a test tube. Carefully add 1 ml of glacial acetic acid and 1ml of hydroiodic acid, using a pipette. Add a boiling chip and insert a gauze plug into the test tube, about 4cm from the mouth, making sure that it is a good fit. Then place non-absorbant cotton on top, and gently push down with a galss rod to make a disk a couple of mm thick. Fold a piece of filter paper, moisten with mucuric nitrate, and place on the cotton disk.

This reaction must be done in a hood

Immerse the test tube into an oil bath, set at 120-130°C. As the mixture boils, vopours rise through the porous plug, (it doesn't matter if it turns grey). The resulting vapour, (an alky halide) reacts with the mercuric nitrate to form a light orange colour. This is because mecuric iodide is formed

Acid Hydrolysis

Heat the ester under reflux with dilute acid i.e. dilute hydrochloric acid. The ester will react with the water present to form a carboxylic acid and an alcohol. Use an excess of water to get a larger yield of organic acid and alcohol. You will then be able to test for the alcohol using acidified potassium dichromate (VI), and a green colour indicates a carboxlyic acid is present

Aldehydes

Ketones

Carboxylic Acids

Phenols

Alcohols

Esters

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