SYNTHESIS OF HEXAN-2-OL

• Place 31.9 g (0.1 mol) of mercury(n) acetate and 100 ml of water in a 1 -litre three-necked flask fitted with an efficient mechanical stirrer, a dropping funnel and a thermometer.

• Stir until the acetate has dissolved and then run in rapidly 100 ml of tetrahydrofuran; an orange-yellow suspension forms almost immediately.

• After stirring for a further 15 minutes, add 8.4 g (12.5 ml,0.1 mol) of hex-1-ene, whereupon the colour is rapidly discharged.

• Stir the mixture at room temperature for 1 hour to ensure completion of the oxy-mercuration step.

• Next add with vigorous stirring 100 ml of 3 m sodium hydroxide solution, followed by a solution of 1 .9 g (0.05 mol) of sodium boro-hydride in 100 ml of 3 m sodium hydroxide.

• Control the rate of addition of both solutions so that the temperature of the reaction mixture remains at about 25 °C, cooling the flask in cold water from time to time if necessary.

• Reduction occurs readily with the separation of elemental mercury.

• Finally stir vigorously at ambient temperature for 3 hours and then allow the reac-tion mixture to remain overnight in a separating funnel supported over a large empty conical flask.

• Separate the mercury layer (19.25 g, 96%) and then the aqueous alkaline phase, retaining the organic layer.

• Saturate the aqueous phase with sodium chloride, remove the additional organic layer which separates and extract the aqueous phase with two 30 ml portions of ether.

• Combine both of the organic layers with the ether extracts and remove most of the organic solvent carefully under reduced pressure using a rotary evaporator; stop the evaporation when two phases begin to separate.

• Add 50 ml of ether and 20 ml of water, separate the ether layer and wash it with four 25 ml portions of water, and dry it over anhydrous calcium sulphate.

• Remove the ether by flash distillation and distil the residue, collecting the hexan-2-ol at 136-140 °C; the yield is 6.9 g (68%).

• Check the purity by g.l.c. on a 10 per cent Silicone oil column at 100 °C, nitrogen flow rate 40 ml per minute.

• The retention time is 1.42 minutes (cf. hexan-1-ol, 1.96 minutes).

Cognate preparation: 1-Phenylethanol

• Use 10.4g (11.5ml, 0.1 mol) of styrene, and carry out the oxymercuration and reduction as described above.

• The yield of recovered mercury is 17.5 g (87%), and traces continue to separ-ate during the work-up procedure.

• Distil the final crude product under reduced pressure and collect the 1-phenylethanol at 110-1 15 °C/25mmHg.

• Towards the end of the distillation the decomposition of residual organo-mercurial compounds ensues, and co-distillation of mercury contaminates the product; collect the contaminated fraction separately.

• The first fraction, yield 6.2 g (51%), is 92 per cent pure by g.l.c. (retention time 5.33 minutes); the impurity is mainly styrene (t R 2.16 minutes).

• The mercury-contaminated fraction (3.0 g, 25%) is 85 per cent pure by g.l.c.