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 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. 60-63шC. Yield, 30g. (20ml).

Chloroform is a colourless liquid, of bp 61ш 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

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Chloroform from Sodium Hypochlorite and Acetone

by Cheapskate

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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 around $4.00 from the local homeowner store in the swimming pool section labeled, "Liquid Pool Chlorine." Make sure you get the Sodium Hypochlorite, not the Hydrochloric Acid that's in the same section, HCl is useful, but not for this reaction.

Add 5 pounds of ice to the Hypochlorite. Be careful pouring this stuff, it's bleach, but twice as strong as the stuff Mom uses to do your laundry. Each splash on your clothing will eat a nice white hole. Stir with a plastic or wooden spoon, avoid metal. Metal spoons won't spoil the reaction, but it may spoil the spoon.

While the solution cools, measure out 340 grams of acetone into a container. Add about half of the measured acetone into the ice solution and stir it up. Wait about 10 minutes and feel the side of the bucket. It should feel warmer near the bottom and colder as you raise your hand to the ice. Stir the ice mix around and equalize the temperature. Add the rest of the acetone and stir again. Let it set for about 10 minutes.

If you didn't listen and used less than five pounds of ice in the solution, it will get hot enough to boil off the Chloroform and leave you with nothing but a bad smell, splatters where it boiled over and probably holes in your shoes and clothes. As a matter of fact it would be good to have an extra five pounds of ice around in case you're doing this in the middle of the day in Panama where the temperature is hovering around 104F. At this temperature, or if you're doing this in the Peruvian Mountains at 6500 feet it may take more ice to keep it cool enough not to boil off the Chloroform as it forms. This is a very exothermic reaction, but it can be controlled easily by the addition of ice as needed.

You should have a cool mixture of ice and something that is starting to look cloudy. It will be colder on the top than the bottom and most of the ice has melted. Let this mixture set until the ice completely melts. Grab the bucket and carefully pour off the water and fine white powder leaving behind the Chloroform that has settled to the bottom of the bucket. When you're pouring off the water, it may be hard to see the Chloroform, but trust me, it's in there. The Chloroform is heavier than water and falls to the bottom in a bubble looking blob. The blob will have a white powder clinging to it. Just pour off the water until you can clearly see the blob and then pour blob, water and powder into a smaller, easier to handle