Chloroform [Mann & Saunders, Practical Organic Chemistry, 3rd Ed]

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.

