posted by CMM on .
We did an experiment on the synthesis of n-butyl bromide using n-butyl alcohol and H2SO4. Why does the alkyl halide layer switch from the top layer to the bottom layer at the point where water is used to extract the organic layer? Please Help.
What is the density of butyl alcohol? What is the density of butyl bromide?
The alcohol is on top in the halide OR water. The halide is on the bottom with either.
bromobutane 1.2686 g/cm3
sulfuric acid 1.8g g/cm3
water 1.0 g/cm3
So at start the bromobutane is less dense than the sulfuric acid so forms a layer above the sulfuric acid. On a small scale the reaction is poured into a large volume of ice water and transferred to a separating funnel. The density of the aqueous phase is now close to 1.0 g/cm3 so the bromobutane is more dense and forms the lower layer. The aqueous phase is usually extracted several times with a solvent and the mixture separated by distillation.