SYNTHESIS OF 2,2,2-TRICHLOROETHANOL

• Dissolve 16.5 g (0.1 mol) of chloral hydrate in 20 ml of water in a 200-ml beaker.

• Place a solution of 1 .3 g (0.03 mol) of sodium borohydride in 20 ml of cold water in a small dropping funnel.

• Cool the chloral hydrate in an ice-water bath; add the borohydride solution dropwise (while stirring with a thermometer) at such a rate that the temperature of the solution is maintained at 20-30 °C - the reaction is strongly exothermic.

• When the borohydride solution has been added, allow the reaction mixture to stand at room temperature for 10 minutes; stir occasionally.

• Then add 2 ml of 2.5 m hydrochloric acid dropwise and with stirring to destroy any residual borohydride and finally add a further 5 ml of the acid.

• Add sufficient ether to form two distinct layers, separate the ether layer, wash it with a little water and dry over magnesium sulphate.

• Remove the ether on a rotary evaporator and distil the residue from an air bath. Collect the 2,2,2-trichloroethanol at 151-153 °C.The yield is 9.8 g (65%).

Cognate preparation: m-Nitrobenzyl alcohol

• Clamp a 500-ml three-necked flask, equipped with a mechanical stirrer, a thermometer and a burette, above the bench so that an ice bath can be placed beneath it.

• Place a solution of 15.1 g (0.1 mol) of m-nitrobenzaldehyde in 100 ml of methanol in the flask and, while stirring, add a solution of sodium borohydride (1.4g, 0.037 mol NaBH 4 in 2 ml of 2 m sodium hydroxide diluted with 18 ml of water) at the rate of 0.5 ml per minute, with occasional cooling to keep the reaction at 18-25 °C.

• When about three-quarters of the solution has been added, there is no further tendency for the temperature to rise, and the addition is stopped.

• Treat a small portion of the reaction mixture with dilute sulphuric acid: hydrogen should be evolved.

• Remove most of the methanol by distillation on a steam bath, and dilute the residue with 100 ml of water.

• Extract the mixture with ether, wash the upper layer with water and dry it rapidly with a little anhydrous magnesium sulphate.

• Remove the ether by flash distillation and distil the residual pale yellow oil under diminished pressure.

• Collect the m-nitrobenzyl alcohol at 183-185 °C/1 7 mmHg; it solidifies to a pale yellow solid, m.p. 30 °C, when cooled in ice. The yield is 13 g (85%).