Question

1. Mineral oil is a non polar solvent. Why would this solvent be a poor choice to replace ethyl acetate in an extraction? (From a mixture of benzil and benzoic acid)

2. During an extraction and recrystallization experiment why is some compound lost each time it is washed with fresh cold solvent while in the Büchner funnel

Answer 1

Mineral oil is an unsaturated fat with multiple double and triple bond in its hydrocarbon chain (,which is basically an ester of log chain fatty acid and glycerol). It is highly non polar in nature.

As benzil is non polar it will be soluble mineral oil,and benzoic acid will be less soluble in oil due to polar nature.Benzoic acid is separated from the mineral oil using aqueous NaOH(base) ,it goes into the aqueous layer.

Benzil needs to be extracted from oil by evaporating the solvent ,which is not possible with mineral oil due to its considerably high boiling point.Thus, ethyl acetate with low b.pt is suitable for the purpose