PREPARATION OF GRIGNARD REAGENT

During the preparation of a Grignard reagent, it is important to exclude moisture.
So the apparatus consisting of a tapered flask, Magnetic Stirrer bar and a Liebig condenser should be assembled while it is still warm after drying in an oven at about 1200C.
The top of the condenser is sealed with a septum cap and fitted with a hypodermic needle attached to a drying tube.

The condenser is connected to the cold water supply.
Before the apparatus assembled, weigh out about 30mg of magnesium turnings and put them into the tapered flask.
Then add a small crystal of iodine.a
Transfer 100micro lit of Bromo Benzene at a 156mg to a small specimen tube and dissolve it in 1 cubic cm of diethyl ether that has been dried over sodium wire.
Cap the tube.
Take out about 0.3 cubic cm of the Bromo Benzene solution in hypodermic syringe fitted with a 15cm needle.
Insert the needle through the septum cap as far as it will go.
Inject the solution onto the magnesium.
Then start the stirrer.
As the reaction begins, the initially brown solution becomes colorless and the ether begins to boil.
If it is slow to start, it can be heated with a hot air blower.
Once the reaction starts, add the rest of the Bromo-Benzene solution drop-wise.

When the addition is complete, remove the syringe, raise the apparatus, then put a  sand  bath  unto the hot plate, lower the flask into the sand and begin heating the bath up to about 600C.
Stir and heat the reaction mixture on the reflux for 30mins.
Measure out 100 microlit of propyol phenol, add to it 0.5 cubic cm of dry di-ethyl ether
Haven taken away the sand bath, and allow the reaction mixture to cool,
Insert the hypodermic syringe containing the propyol phenol solution to the septum cap and add it clockwise.
There is an exothermic reaction.

When all pro solution has been added, replace the sand bath and heat the stirred reaction mixture under reflux for a further 10mins.
Then remove the apparatus from the sand bath to allow the reaction mixture to cool.
When it has cooled, remove the flask from the condenser.
Transfer the reaction mixture into a small specimen tube containing cold dilute sulphuric acid.

 Rinse the reaction vessel with a further 0.5 cubic cm of Di-ethyl ether and add the rinsing to the tube.
Mix the two layers repeatedly until both are clear.
Allow the layers to separate.
Then pipette out the water layer (the bottom layer) into another container.

Dry the remaining Di-ethyl ether solution of the product with anhydrous magnesium sulphate.
Filter the Di-ethyl ether solution through a cotton wool plug into a clean dry tube.
Rinse the drying agent and the filter with a little more ether.
Expel the last traces of ether from the filter by pressure from a rubber teeth.
Add an anti-bumping granule and carefully boil off the Di-ethyl ether.
Remove the last traces of solvent and pushing the tube down into the sand.
The Residue should solidify on cooling and can be purified by re-crystallization.