[Archer]

Hydronium. So are you saying that by adding water the reaction finishes?

Not just water, you need to make the solution acidic to convert R-O-Mg-Br to R-OH.

Generally it is not wise to add too strong an acid as this can cause a violent reaction. Common Practice is to add saturation Ammonium Chloride carefully (dropwise) untill the evolution of H₂ ceases.

Next you add water to solubilise the resultant inorganic salts, followed by ether.

Now you can separate the two layers, keeping the organic layer. Which layer do you think this will be? Top or bottom?

[ih]

Well ether will be on top so I think it will be the top.

[Archer]

Ok, so you separate the ether and put it to one side, then you wash the aqueous phase with ether a couple more times to ensure that you have as much of your alcohol extracted as possible.

Now you will need to combine the ether washing and wash them to remove any inorganics which may be in suspension.

How would you do that? What is the best way to make Mg²⁺ water soluble?

[ih]

So I've separated the water and ether, the alcohol is in the ether. Heating water increases solubility, would that be how?

[Archer]

So I've separated the water and ether, the alcohol is in the ether. Heating water increases solubility, would that be how?

No, hot water and ether is not a good combination, look up the boiling point of ether.

You wash at least twice with dilute acid, 1M HCl should be strong enough to make MgCl₂ which is soluble in water and it is not so strong that you risk dehydrating your product.

Now you need to remove the excess acid from the ether, how is this achieved?

[ih]

Add water and then do another extraction?

[Archer]

Add water and then do another extraction?

During the washing stages you don't extract the aquous phases with more ether, you just put them to one side until you are satisfied that the product is in your organic phase (I lost count of the number of students who washed their product down the sink by mistake)

Ideally water would be the last wash, you need to neutralise the acid with something mild. What could you use?

[ih]

sodium bicarbonate?

[Archer]

sodium bicarbonate?

Yes, good.

Now a water wash or two to clear out the residual bicarb solution and you are ready to dry over Magnesium sulphate and filter.

Removal of the solvent should yield your product. Wether or not you need to purify by preparative chromatography will be evident from TLC and GLC analysis. With luck your product should be sufficiently pure for the Williamson Ether Synthesis.

[ih]

Thanks so much!
Any clues how I would remove iodide from the solution after the Williamson ether synthesis?

[Archer]

It is important to remember to make sure your glassware is oven dried (and cooled) and under an inert atmosphere before you do a Grignard reaction, otherwise your yields will suffer and Grignard Reagents can cause a fire when they are added to water.

[Archer]

Thanks so much!
Any clues how I would remove iodide from the solution after the Williamson ether synthesis?

draw the mechanism for the reaction and, taking into account what we have just discussed, give us your thoughts.

[ih]

What do you mean by this?

dry over Magnesium sulphate and filter.

I could create a salt with the iodide. Because it is negatively charged I wont add an acid would I? Would a base work?

[Archer]

What are the reactants of Williamson Ether Synthesis? Write a balanced equation to see what products are formed.

[ih]

3-pentanol + methyl iodide ==> 3-methoxypentane + H+ + I-
will the H+ and I- form a salt?