THE PREPARATION AND PURIFICATION OF REAGENTS

These are readily prepared by the interaction at 0 °C of the alcohol with sodium nitrite in the presence of excess of concentrated sulphuric acid. 

(1) Care must be exercised in handling pentyl and the other alkyl nitrites inhalation of the vapour may cause severe headache and heart excitation. The preparation must therefore be conducted in an efficient fume cupboard. 

Hexyl nitrite may be prepared similarly by using 95 g (1.38 mol) of AnalaR sodium nitrite in 375 ml of water a mixture of 25 ml of water, 62.5 g (34 ml) of concentrated sulphuric acid and 127.5g (156ml, 1.25 mol) of hexan-l-ol. The yield of crude product is 124g (76%). B.p. 129-130.5 °C or 52°C/44mmHg. 

For butyl nitrite use the same quantities as for hexyl nitrite, but with 92.5 g (114 ml, 1.25 mol) of butan-l-ol replacing the hexan-l-ol. The yield of crude product is 110 g (85%). Butyl nitrite boils at 76.5-77.5 °C at atmospheric pressure with slight decomposition, but distils unchanged at 27 °C/43 mmHg. 

Ethyl nitrite may be prepared by dissolving 38 g (0.55 mol) of sodium nitrite in 120 ml of water in a 500-ml flask equipped as above. Dilute 23 g (29 ml, 0.5 mol) of ethanol with an equal volume of water, carefully add 25 g (13.5 ml) of concentrated sulphuric acid and dilute to 120 ml with water. Cool both solutions to -10°C in an ice-salt bath and add the acid-alcohol mixture to the nitrite solution slowly with constant stirring during about 30 minutes. Transfer the reaction mixture to a cooled separating funnel, run off the lower aqueous phase, wash the ethyl nitrite layer rapidly with ice-cold 2 per cent sodium hydrogen carbonate solution and dry over anhydrous sodium sulphate. The product may be kept at 0°C as a 50 per cent solution in absolute ethanol if required but should be used as soon as possible. The b.p. of pure ethyl nitrite is 17°C. 

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