Synthesis of Chloroform
Synthesis of Chloroform
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With Calcium Hypochlorite and Acetone
When chlorine is passed into boiling alcohol, both chlorination of the methyl group and oxidation of the primary alcohol group to an aldehyde occur, giving trichloro-acetaldehyde or chloral: When chloral is treated with caustic alkali, fission of the C-C linkage occurs, giving chloroform and a formate. Acetaldehyde and also many ketones, such as acetone, containing the CH3CO- group behave similarly when treated with calcium or sodium hypochlorite, chlorination of the CH3CO- group being immediately followed by fission of the molecule by the alkali present in the hypochlorite solution. The acetone method clearly gives a much cheaper product than the alcohol method.
Required: Calcium Hypochlorite 100g (bleaching powder), acetone 44ml
Place 100g of calcium hypochlorite in a mortar and add 250 ml of water in small quantities at a time: between each addition grind the mixture of bleaching powder and water well together and decant the cream-like suspension through a funnel into a 1-litre flat-bottomed flask. Finally, when all the water has thus been used, only a gritty residue remains in the mortar. Fit the flask with an efficient reflux water-condenser, pour 44ml (35g) of acetone in small quantities, at a time, down the condenser and mix by thorough shaking after each addition. The reaction usually starts spontaneously after a few minutes, and a bath of cold water should be available into which the flask may be dipped if necessary to moderate the reaction. Should the reaction show no signs of starting within 5 minutes of the addition of the acetone, warm the flask cautiously on a boiling water-bath until the reaction starts, and then remove it immediately. When the vigorous boiling has subsided, heat the flask on a boiling water-bath for a further 5-10 minutes (not more) to complete the reaction. Cool the flask in
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With Calcium Hypochlorite and Acetone
When chlorine is passed into boiling alcohol, both chlorination of the methyl group and oxidation of the primary alcohol group to an aldehyde occur, giving trichloro-acetaldehyde or chloral: When chloral is treated with caustic alkali, fission of the C-C linkage occurs, giving chloroform and a formate. Acetaldehyde and also many ketones, such as acetone, containing the CH3CO- group behave similarly when treated with calcium or sodium hypochlorite, chlorination of the CH3CO- group being immediately followed by fission of the molecule by the alkali present in the hypochlorite solution. The acetone method clearly gives a much cheaper product than the alcohol method.
Required: Calcium Hypochlorite 100g (bleaching powder), acetone 44ml
Place 100g of calcium hypochlorite in a mortar and add 250 ml of water in small quantities at a time: between each addition grind the mixture of bleaching powder and water well together and decant the cream-like suspension through a funnel into a 1-litre flat-bottomed flask. Finally, when all the water has thus been used, only a gritty residue remains in the mortar. Fit the flask with an efficient reflux water-condenser, pour 44ml (35g) of acetone in small quantities, at a time, down the condenser and mix by thorough shaking after each addition. The reaction usually starts spontaneously after a few minutes, and a bath of cold water should be available into which the flask may be dipped if necessary to moderate the reaction. Should the reaction show no signs of starting within 5 minutes of the addition of the acetone, warm the flask cautiously on a boiling water-bath until the reaction starts, and then remove it immediately. When the vigorous boiling has subsided, heat the flask on a boiling water-bath for a further 5-10 minutes (not more) to complete the reaction. Cool the flask in