Synthesis of Chloroform

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Synthesis of Chloroform


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 cold water (to prevent loss of chloroform vapour whilst the apparatus is being rearranged) and then fit the flask with a fairly wide delivery-tube and reverse the water-condenser for distillation. Heat the flask on a water-bath until distillation of the chloroform is complete.

The chloroform thus obtained is usually acidic. Therefore shake it thoroughly with dilute sodium hydroxide solution in a separating-funnel. (If the chloroform tends to float on the alkaline solution, it still contains appreciable quantities of acetone: in this case the soda should be run out of the funnel and the chloroform shaken with water to extract the acetone. The extraction with the soda can then be performed after the water has been removed.) Carefully run off the heavy lower layer of chloroform into a small conical flask, dry it over calcium chloride for 15-20 minutes, and then filter it directly into a 75 ml. distilling-flask fitted with a clean dry water-condenser. Distill the chloroform, collecting the fraction of bp. 60-63øC. Yield, 30g. (20ml).

Chloroform is a colourless liquid, of bp 61ø and d 1.50. It has a characteristic sweetish smell, and is frequently used as a solvent in organic chemistry.

Reference: Mann & Saunders, Practical Organic Chemistry, 3rd Ed


Chloroform from Sodium Hypochlorite and Acetone
by Cheapskate


Go get a five gallon bucket. The ones used for painting work well and are available new, with a cover, in the paint department of most big homeowner stores. The cover can be used to keep bird droppings and bugs out of the reaction. Put the bucket outside in a reasonably ventilated area with good drainage away from any shrubbery that can be killed by spills. Pour two gallons of 10% sodium hypochlorite solution into the bucket. This material is available in two one-gallon containers for...
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