SYNTHESIS OF CYCLOHEXYLMETHANOL (primary alcohol from for maldehyde)

• Equip a 2-litre three-necked flask with a sealed stirrer unit, a 500-m1 separat­ing funnel [which is replaced by a solids addition system in the latter part of the experiment], and an efficient double surface reflux con­denser; place calcium chloride guard-tubes on the top of the funnel and on the condenser. 

• All parts of the apparatus must be thoroughly dry. 

• Arrange the flask so that it may be heated on an oil bath. 

• Place 26.7 g (1.1 mol) of magne­sium turnings (1) and a crystal of iodine in the flask. 

• Measure out in separate vessels 118.5 g (121 ml, 1.0 mol) of cyclohexyl chloride and 450 ml of dibutyl ether. 

• Introduce about 100 ml of pure, dry, dibutyl ether and 15 ml of the chloride into the flask. 

• Warm the flask gently to initiate the reaction and if necessary add a further crystal of iodine. 

• The onset of the reaction is accompanied by the disappearance of the iodine colour, the development of cloudiness and bubbles being released from the metal surface. 

• When the reaction is progressing well, add sufficient dibutyl ether to cover the magnesium and set the stirrer in motion. 

• Add dropwise the remainder of the cyclohexyl chloride dissolved in the remainder of the dibutyl ether at such a rate that the reaction proceeds smoothly. 

• When the solution commences to cool and only a small amount of metal remains, remove the funnel and replace it with the solids addition system containing 100 g (c. 3.3 mol) of dry paraformaldehyde (2). 

• Heat the reaction mixture to 100­110 °C and add the paraformaldehyde in small portions over 2 hours to the well-stirred solution. 

• Continue the heating and stirring for a further half-an­ hour. 

• Cool the mixture, add 300 g of finely crushed ice and agitate the mixture until decomposition is complete. 

• Add twice the theoretical quantity of 30 per cent sulphuric acid to dissolve the magnesium hydroxide, and then steam dis­til the mixture until no more oil passes over (2000-2500 ml). 

• Saturate the distillate with sodium chloride and separate the upper organic layer. 

• Dry with anhydrous potassium carbonate and distil under reduced pressure using a fractionating column; collect the first fraction of dibutyl ether and then a second fraction of cyclohexylmethanol. 

• Add 5 g of freshly dehydrated calcium oxide to the alcohol fraction and heat on a water bath for 30 minutes; this will remove last traces of unreacted halogen compound. 

• Filter, redistil under reduced pressure and collect the fraction of b.p. 88-93 °C/18 mmHg; the yield is 70 g (66%). The boiling point of cyclohexylmethanol at atmospheric pres­sure is 182 °C.

Notes to keep in mind:

1. Commerical magnesium turnings for the Grignard reaction should be washed with sodium-dried ether to remove traces of surface grease which may be present, dried at 100 °C and allowed to cool in a desiccator.

2. Dry the material in a desiccator over phosphoric oxide for 2 days.

Cognate preparations: Hexan-1-ol (primary alcohol from ethylene oxide)

CAUTION: Owing to the toxicity of ethylene oxide and of benzene all opera­tions must be carried out in an efficient fume cupboard.

• Equip a 2-litre three-necked flask as above; the solids addition system is not required but the gas inlet system described below should be assembled for use in the latter stages of the experiment. 

• An appropriate water bath should be used for heating. 

• Place 37.5 g (1.54 mol) of washed and dried magnesium turnings and 300 ml of sodium dried ether in the flask and add a small crystal of iodine. 

• Prepare a solution of 205.5 g (161 ml, 1.50 mol) of pure dry butyl bromide (Expt 5.54) in 300 ml of dry ether in the separatory funnel and intro­duce about 25 ml of the solution into the flask. 

• As soon as the reaction com­mences (disappearance of the iodine colour), set the stirrer in motion and add  the remainder of the butyl bromide solution at such a rate that steady reflux­ing of the reaction mixture is maintained (if the reaction becomes too vigor­ous it should be moderated by momentarily cooling the flask in an ice bath). 

• When the addition is complete, maintain gentle reflux, with the aid of a hot-water bath if necessary, until most of the magnesium has reacted (about 15­30 minutes). 

• Cool the flask in a freezing mixture of ice and salt. 

• Remove the separatory funnel and replace it by a tube, 4 mm in diameter, the end of which is about 2 cm above the surface of the liquid. 

• Attach this delivery tube to a flask fitted with 'wash bottle' tubes, the long tube being nearer the three-necked flask and the other end being connected to a supply of dry nitrogen. 

• Cool this flask in a mixture of ice and salt and introduce rapidly 90g (2.02 mol) of ethylene oxide (1) from a 100 g sealed bulb of the reagent; the latter must, of course, be cooled in an ice and salt mixture before opening (2). 

• Gradually introduce the ethylene oxide into the reaction flask over a period of 1.5-2 hours; the temperature should not rise above 10 °C. 

• When all has been added, remove the freezing mixture sur­rounding the three-necked flask. 

• The temperature of the mixture will gradu­ally rise and the reaction mixture will boil gently. 

• When boiling ceases, reflux on a water bath for 30 minutes. 

• Allow to cool, insert a thermometer into a neck of the flask, arrange the condenser for downward distillation and collect 250 ml of ether in a measuring cylinder; do not collect a larger volume of ether as a violent reaction may set in, apparently due to a rearrangement of the initial reaction product, and considerable loss may ensue. 

• Change the receiver, and introduce 250 ml of sodium-dried benzene (CAUTION) into the reaction mixture. Continue the distillation with stirring until the temperature of the distilling vapour reaches 65 °C. 

• Then boil the mixture under reflux for 30 minutes; generally by this time the mixture has become so viscous that stir­ring is no longer very effective. 

• Allow to cool. 

• Decompose the reaction mix­ture with 500 ml of an ice—water mixture, and dissolve the precipitated magnesium hydroxide with 30 per cent sulphuric acid; add sufficient finely-crushed ice to keep the mixture cold. 

• Steam distil and collect about 2 litres of distillate. 

• Separate the oily layer (A), and distil the aqueous layer until free of hexan-1 -ol; add the oil so obtained to (A). 

• Stir the crude hexan-l-ol on a water bath with 250 ml of 20 per cent sodium hydroxide solution, and steam distil again as before. 

• Dry the oil with a little anhydrous calcium sulphate, distil through an efficient fractionating column and collect the fraction, b.p. 154-157 °C. 

• The yield of hexan-l-ol is 90 g (49%).

Notes to Keep in mind:

1. It is advisable to cool and open the ampoule of ethylene oxide behind a safety screen in a fume cupboard, and to wear plastic gloves and goggles.

2. Instead of adding the liquid ethylene oxide (b.p. 10.5 °C), the latter may be dis­solved in 100 ml of ice-cold anhydrous ether; this solution is added directly to the reac­tion mixture during 15-30 minutes. The yield however is somewhat lower.

Nonan-l-ol (primary alcohol from ethylene oxide). 

• Prepare a Grignard reagent from 24.5 g (1 mol) of magnesium turnings, 179 g (157 ml, 1 mol) of 1-bromoheptane and 300 ml of dibutyl ether as described above. 

• Cool the solution to 0 °C and, with vigorous stirring, add an excess of ethy­lene oxide. 

• Maintain the temperature to 0 °C for 1 hour after the ethylene oxide has been introduced, then allow the temperature to rise to 40 °C and maintain the mixture at this temperature for 1 hour. 

• Finally heat the mixture on a water bath for 2 hours. 

• Decompose the addition product by pouring the cooled reaction mixture into ice-water, acidify with sulphuric acid to dissolve the precipitated magnesium hydroxide and isolate the reaction products as described in the procedure for hexan-1 -ol. 

• Collect the nonan-l-ol at b.p. 95-100 °C/12 mmHg; the yield is 95 g (69%).