Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: wseguins on August 12, 2014, 02:53:28 PM
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Hello guys, I'm doing production chloroacetone. However, I had only 16% yield. Do you know what I can do to improve this performance using the methodology below?
250 ml acetone are placed in a flask and cooled in a waterbath to about 5°C. 3 ml H2SO4 and 3 ml HCl (30% suffices) are added.
50 g TCCA (trichloroisocyanuric acid) are crushed and dissolved in 150 g hot acetone. After all TCCA is dissolved or at least broken down to a very fine powder the mixture is cooled to about 5°C.
Some crushed ice is prepared.
The TCCA in acetone is added in portions over two hours to the acetone/HCl/H2SO4. The mixture turns greenish after every addition - chlorine. The next addition has to wait until the greenish color has disappeared and the mixture has cooled down again. Patience! Crushed ice is added to the waterbath as needed, the temperature should always stay below 10°C. Stirring or swirling with every addition is advised.
Just waiting 15 minutes after each addition of TCCA works fine.
Let sit for 4 hours and the cyanuric acid will settle. Decant the liquid, filter and add 50 g chalk, preferable in chunks, or pieces of broken marble.
The cyanuric acid is extracted twice with 100 ml hot acetone. The filtered extracts are joined with the first decanted acetone/chloroacetone mixture with the chalk.
Let settle, decant and filter and distill using a column. To the distillation flask some 10 g marble or chalk are added.
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What are the byproducts? If you aren't seeing the polychlorinated acetones, the reagents can be combined faster. Use more concentrated acids, so less water is present which quenches the reagent by formation of HClO. A alternative to sulfuric acid is phosphoric acid or boric acid(s). Why hot acetone+TCCA? Have you tried adding cosolvent such as DCM instead of heat? Was the % yield calculated before or after the distillation?
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What are the byproducts? If you aren't seeing the polychlorinated acetones, the reagents can be combined faster. Use more concentrated acids, so less water is present which quenches the reagent by formation of HClO. A alternative to sulfuric acid is phosphoric acid or boric acid(s). Why hot acetone+TCCA? Have you tried adding cosolvent such as DCM instead of heat? Was the % yield calculated before or after the distillation?
Sincerely, I do not know what are the byproducts, never made it resonance. The water can be a factor to be considered by me, but I think I'll need a stronger acid than boric acid. I use hot acetone, because the cold does not dissolve well TCCA. The yield was calculated on the distillate.
Do you produce Chloroacetone? What methodology do you use?
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Use DCM until it all dissolves, and don't heat the acetone up. Take a crude NMR after the reaction, and add a standard e.g. N(Me)4Cl to determine yield. Doing so will tell you what to change. The paper that suggested boric acid reported 100% yield under the same conditions with 1:1.01 equivalents, and I have also seen BF3 used.
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Use DCM until it all dissolves, and don't heat the acetone up. Take a crude NMR after the reaction, and add a standard e.g. N(Me)4Cl to determine yield. Doing so will tell you what to change. The paper that suggested boric acid reported 100% yield under the same conditions with 1:1.01 equivalents, and I have also seen BF3 used.
Thank you, I will try these suggestions.
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Use DCM until it all dissolves, and don't heat the acetone up. Take a crude NMR after the reaction, and add a standard e.g. N(Me)4Cl to determine yield. Doing so will tell you what to change. The paper that suggested boric acid reported 100% yield under the same conditions with 1:1.01 equivalents, and I have also seen BF3 used.
Do you have the paper that uses boric acid to produce chloroacetone?
I did not find it in the literature.
Thanks!
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It was one of the first results in SciFinder. Do you know how to use SciFinder?
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Why not ask this at sciencemadness, which is where you got this prep from and the original author still hangs out there?
I have done this prep a bunch of times and got good yields. I would be suspecting operator error.
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Distilling tear gas. Fun.
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It's a good time.