Experiment 338,2. P.338. Preparation of oil of wintergreen.

Procedure

Reason

Result

1.       add to the flask 9g of 2hobenzoic acid, 15cm methanol, 2cm conc. sulphuric acid, reflux about an hour.

hoacid+ methanol>oil of wintergreen + water, acid is catalyst in esterification

<>-CO₂CH₃

<>-OH is formed

2.       cool mixture to room temp. and pour into a separating funnel containing 30cm cold water, rinse flask with some ethylethanoate solvent, shake the funnel and allow to settle.

to wash away aqueous impurities. When rinsing open the tap occasionally to release pressure. Ethylethanoate is used to collect all product. Called solvent extraction. If the mixture contains crystals filter!

to layers form, upper is organic that we want, lower is water.

3.       run lower layer to the conical flask (don't throw away yet), wash the organic with 30cm 0.5M NaCO3

Neutralise the acid, release the pressure often! Organic acid left is now on solvent. U can let the lower layer go.

No more benzoic acid left

4.       Dry with anhydrous sodium sulphate and filter under gravity.

Get rid of all the water that remains on solid sulphate. Allow to stay overnight. Don't use Buckner as it would remove H2O from sulphate

dry oil of wintergreen

5.       distillate collecting everything above 220C

heat in water-bath to remove all organic impurities

pure product, distinctive smell.

6.       Calculate the yield

mark also the flask

useful product for next react