Benzyl Alcohol and Benzoic Acid from Benzaldehyde and Strong Potash (Cannizzaro, Gattermann 1914)

Strong potash splits benzaldehyde in two: half is reduced to benzyl alcohol, half oxidised to benzoic acid (as potassium benzoate). 20 g of benzaldehyde gives about 8 g of benzyl alcohol, boiling at 206 °C; the benzoic acid is thrown down with hydrochloric acid. Not given: the volumes of water and ether, the amount of hydrochloric acid and the benzoic acid yield. Source: L. Gattermann, Practical Methods of Organic Chemistry (1914 ed.), Reaction 25, pp. 303-304. Picture: our drawing.

中级

1 night plus a few hours

说明

Shake with strong potash

Dissolve 18 g of potassium hydroxide in 12 g of water and let it cool. Put 20 g of benzaldehyde in a stoppered cylinder or other thick-walled vessel, add the cold potash and shake until a lasting emulsion forms.

此步骤所需材料：

苯甲醛1 20 g

氢氧化钾1 18 g

水1 12 g

所需工具：

称重秤

量筒

软木塞

Stand overnight

Close the vessel with a cork, not a glass stopper (a glass stopper can stick fast), and let it stand overnight. A crystalline paste of potassium benzoate separates.

所需工具：

量筒

软木塞

Extract with ether

Add water until the paste dissolves to a clear solution. Shake it out several times with ether to take up the benzyl alcohol, keeping the watery alkaline layer for the benzoic acid.

此步骤所需材料：

水1 amount not given