The presence of a hydroxyl group in an unknown organic compound may be detected with the help of following tests. If the compound is a slid it is dissolved in an inert solvent, e.g., dry ether or benzene.
i) Alcohols are neutral substances towards litmus:- the colour of blu or red litmus does not change when alcohol is added to it.
ii) Ceric ammonium nitrate test:- the freshly prepared solution of ceric ammonium nitrate has yellow color. When few drops of this reagent are added to the given compound or its solution if color changes from yellow to red the compound contains a hydroxyl group.
iii) Sodium metal test: - A small piece of sodium metal is added to the compound or its solution. Evolution of hydrogen gas indicates the presence of –OH group in the organic compound.
iv) Phosphorus pentachloride test:- phosphorus pentachloride is added to the given compound or its solution, if it becomes warm with volution of hydrogen chloride, the organic compound contains a hydroxyl group.
v) Acylation test:- acetyl chloride or benzoyl chloride is added to the given compound or its solution, if hydrogen chloride is evolved, it shows that the organic compound is an alcohol.