SYNTHESIS OF HEPTAN-2-OL

STEP 1: Place a mixture of 114 g (140 ml, 1.0 mol) of heptan-2-one (1), 300 ml of recti­fied spirit (95% ethanol) and 100 ml of water in a 1.5-litre three-necked flask fitted with an efficient double surface condenser and a thermometer dipping into the reaction mixture. 

STEP 2: Through the third neck add 65 g (2.8 mol) of clean sodium, preferably in the form of wire although small pieces may be used with somewhat inferior results, gradually and at such a rate that the reaction is under control; cool the flask in running water or in ice during the addition. 

STEP 3: The temperature should not rise above 30 °C. When the sodium has completely reacted, add 1 litre of water and cool the mixture to about 15 °C. 

STEP 4: Separate the upper layer, wash it with 25 ml of dilute hydro­chloric acid (1:1), then with 25 ml of water, and dry with anhydrous potas­sium carbonate or anhydrous calcium sulphate. 

STEP 5: Distil through an efficient fractionating column and collect the heptan-2-ol at 156-158 °C. The yield is 75 g (65%).

Notes to keep in mind:

1. The ketone may be synthesised; it is also available commer­cially. The latter should first be dried, redistilled, and the fraction, b.p. 150-152 °C, col­lected.

Cognate preparations. Hexan-2-ol. 

• Dissolve 100 g (123 ml, 1 mol) of hexan-2- one in 750 ml of ether, add 150 ml of water and stir the mixture vigorously. 
• Introduce 69 g (3 mol) of clean sodium in the form of wire (or small pieces) as rapidly as possible; the reaction must be kept under control and, if necessary, the flask must be cooled in ice or in running water. 
• When all the sodium has reacted, separate the ethereal layer, wash it with 25 ml of di­lute hydrochloric acid (1:1), then with water, dry with anhydrous potassium carbonate or with anhydrous calcium sulphate and distil through a fraction­ating column. 
• Collect the fraction of b.p. 136-138 °C. The yield of hexan-2-ol is 97 g (95%).

Cyclopentanol. Use cyclopentanone and proceed as for hexan-2-ol. Collect the cyclopentanol as a fraction of b.p. 139-142 °C.