The Hive > Methods Discourse

mono-Chloroacetic acid synthesis

(1/2) > >>

While reading some organic chemistry books searching the Hive I came up with an idea of performing this synth. Hope it hasn't been posted before.


Prepare a mixture of 13g red phosphorus and 143mL of glacial acetic acid in a 250mL RB flask. Connect a Claisen adapter to the flask; attach a reflux condenser to the side arm, and a thermometer adapter to the straight arm. Then place a gas inlet tube into the thermometer adapter.

Place the apparatus on direct sunlight if possible. The sunlight is very important as the light provides the  energy necessary for this reaction to complete. Ordinary  light bulb will not work, so this reaction should be performed during summer. With adequate sunlight the reaction will require ~12 hours and in winter it will require two or more days. The longer it takes, the more chlorine will be wasted.

When you have your setup placed on a sunlight start heating the flask on a boiling water bath and pass the current of dry chlorine into the acetic acid. [Note: Chlorine gas prepared from potassium permanganate and HCl can be dried by passing it through conc. H2SO4]. After ~12 hours of bubbling the chlorine gas take a small sample into a test tube and cool it in an ice water bath. It should solidify after rubbing the walls of a test tube with a glass stirring rod. If that happens the reaction is complete and you can set up your flask for a simple distillation. Collect the portion distilling between 160 and 190° C. Cool the distillate in a salt-ice bath and rub the walls with a glass stirring rod. The cristals that form are filtered with suction. The filtrate is then redistilled, this time collecting the portion between 175 and 190° C. The crystals are obtained and filtered as before. The combined portions of crystals are distilled to obtain pure chloroacetic acid. Yield ~100g.

You can also use sulfur as an alternative for red phosphorus as discussed several times here on the Hive.

Life without chemistry would be a mistake.

Is it a synthesis taken directly from that book (if so, which one?), or did you extrapolate from a general outline for the preparation of alpha-halocarboxylic acids (Hell-Vollhard-Zelinsky reaction, right?). I believe the general reaction has been discussed before, as a lot of people wanted to prepare alpha-bromopropionic acid a few moths ago (as that was a very simple step from nitroethane), but I don't think an actual chloroacetic acid synthesis has been posted.

I know chloroacetic acid is a solid at room temperature, but I have forgotten its melting point. Perhaps it is a good idea to not keep the water in the distillation condenser too cold, or it will all crystallize and clog the condenser.

mp. of acetic acid: 16.7 deg celcius
mp. of chloroacetic acid: 59 deg celcius.

The synthesis isn't taken directly from any book. It's true, I read some threads about the preparation of alpha-halocarboxylic acids here on the Hive and that is how I came up with idea for this synth. The only book that was used is J.B.Hendrickson, D.J.Cram, G.S.Hammond, Organic Chemistry, 3rd edition, McGraw-Hill, New York, 1970.
Life without chemistry would be a mistake.

You mean that the synthesis hasn't been tested, it is just an adaption from other texts by you?


[0] Message Index

[#] Next page

Go to full version