[seaton]

Dear all,

I am doing a synthesis of methacryloyl chloride with 1-amino-2-propanol, I feed 1.5 equivalent of methacryloyl chloride with 1 equivalent of 1-amino-2-propanol. After the reaction, I got almost full conversion of 1-amino-2-propanol and around 0.5 equivalent methacryloyl chloride. Then I am thinking how to remove the unreacted methacryloyl chloride. Do you guys think it is possible to purify it by passing the crude product through an aluminum oxide column as methacryloyl chloride is pretty polar? Or I can wash the crude product with NaOH and convert the unreacted methacryloyl chloride to methacrylic acid and then pass the crude product through an aluminum oxide column.

Please let me know what you think about the purification? All your ideas are appreciated.

Thanks for your time.

Regards,
John

[discodermolide]

Dear all,

I am doing a synthesis of methacryloyl chloride with 1-amino-2-propanol, I feed 1.5 equivalent of methacryloyl chloride with 1 equivalent of 1-amino-2-propanol. After the reaction, I got almost full conversion of 1-amino-2-propanol and around 0.5 equivalent methacryloyl chloride. Then I am thinking how to remove the unreacted methacryloyl chloride. Do you guys think it is possible to purify it by passing the crude product through an aluminum oxide column as methacryloyl chloride is pretty polar? Or I can wash the crude product with NaOH and convert the unreacted methacryloyl chloride to methacrylic acid and then pass the crude product through an aluminum oxide column.

Please let me know what you think about the purification? All your ideas are appreciated.

Thanks for your time.

Regards,
John

If you wash with concentrated enough NaOH solution you should obtain the sodium salt of methacrylic acid which will remain in the aqueous layer.
Do you need so much excess? This reaction must almost be like a titration, try the reaction with 1.05 equivalents, you can always add more if it does not go to completion.

[orgopete]

The amine should be the most reactive, but because the reaction is acidic, you may experience some N to O acyl migration, thus forming the ammonium salt of the ester.

I can understand the thinking an excess of acid chloride is needed because the HCl liberated will tie up the amine as an ammonium salt and retard the reaction. I suggest you use just one equivalent of your acid chloride and use an acid acceptor, like pyridine.

Methacryloyl chloride should be sufficiently reactive that it will decompose in water. Just washing extracts with acid should remove unreacted amine and excess pyridine and bicarbonate or other base will remove any acidic materials.

[seaton]

The amine should be the most reactive, but because the reaction is acidic, you may experience some N to O acyl migration, thus forming the ammonium salt of the ester.

I can understand the thinking an excess of acid chloride is needed because the HCl liberated will tie up the amine as an ammonium salt and retard the reaction. I suggest you use just one equivalent of your acid chloride and use an acid acceptor, like pyridine.

Methacryloyl chloride should be sufficiently reactive that it will decompose in water. Just washing extracts with acid should remove unreacted amine and excess pyridine and bicarbonate or other base will remove any acidic materials.

Thanks for your reply. I do have a base (triethylamine) in the reaction to bind with HCl. Do you suggest me to get rid of methacrylyol chloride by washing with a acid (why not a base?).

[nox]

I think pete's suggesting you first do an acid wash to remove any unreacted starting materials, then do a base wash to get rid of any methacryloyl chloride.

[orgopete]

… I do have a base (triethylamine) in the reaction to bind with HCl. Do you suggest me to get rid of methacrylyol chloride by washing with a acid (why not a base?).

You didn't tell us that. I think you should be able to isolate a more pure product simply by changing the stoichiometry. 1.5 equivalents of an acid chloride with a bifunctional reagent, I say mixture. I'd be surprised if you didn't get a substantial amount of ester amide.

I suggested acid to remove any amines, catalyst or starting material. Base to remove any acids from reaction of acid chloride with water.

How are you monitoring your reaction?

[discodermolide]

I think pete's suggesting you first do an acid wash to remove any unreacted starting materials, then do a base wash to get rid of any methacryloyl chloride.

You do not need to wash with water to remove methacryloyl chloride as I suggested NaOH solution will do it.

[seaton]

… I do have a base (triethylamine) in the reaction to bind with HCl. Do you suggest me to get rid of methacrylyol chloride by washing with a acid (why not a base?).

You didn't tell us that. I think you should be able to isolate a more pure product simply by changing the stoichiometry. 1.5 equivalents of an acid chloride with a bifunctional reagent, I say mixture. I'd be surprised if you didn't get a substantial amount of ester amide.

I suggested acid to remove any amines, catalyst or starting material. Base to remove any acids from reaction of acid chloride with water.

I did monitor it. The reactoin was pretty fast, after 1 h I did not see more reaction, but it was not complete as I always see a bit unreacted amine left.
How are you monitoring your reaction?

[seaton]

I think pete's suggesting you first do an acid wash to remove any unreacted starting materials, then do a base wash to get rid of any methacryloyl chloride.

You do not need to wash with water to remove methacryloyl chloride as I suggested NaOH solution will do it.

Thanks for your suggestion. The product is also water soluble, that is why I do not want to wash the crude product but use a column. Do you have any idea how to wash a water soluble product?

[discodermolide]

I think pete's suggesting you first do an acid wash to remove any unreacted starting materials, then do a base wash to get rid of any methacryloyl chloride.

You do not need to wash with water to remove methacryloyl chloride as I suggested NaOH solution will do it.

Thanks for your suggestion. The product is also water soluble, that is why I do not want to wash the crude product but use a column. Do you have any idea how to wash a water soluble product?

Well after all that you now say the product is water soluble, no comment.
Try extracting the mixture with toluene to remove the organic bits.

[seaton]

I think pete's suggesting you first do an acid wash to remove any unreacted starting materials, then do a base wash to get rid of any methacryloyl chloride.

You do not need to wash with water to remove methacryloyl chloride as I suggested NaOH solution will do it.

Thanks for your suggestion. The product is also water soluble, that is why I do not want to wash the crude product but use a column. Do you have any idea how to wash a water soluble product?

Well after all that you now say the product is water soluble, no comment.
Try extracting the mixture with toluene to remove the organic bits.

Thanks for your advice, I will try toluene. I got another idea of using saturated NaCl water solution to wash. Do you think it can work?

[discodermolide]

I think pete's suggesting you first do an acid wash to remove any unreacted starting materials, then do a base wash to get rid of any methacryloyl chloride.

You do not need to wash with water to remove methacryloyl chloride as I suggested NaOH solution will do it.

Thanks for your suggestion. The product is also water soluble, that is why I do not want to wash the crude product but use a column. Do you have any idea how to wash a water soluble product?

Well after all that you now say the product is water soluble, no comment.
Try extracting the mixture with toluene to remove the organic bits.

Thanks for your advice, I will try toluene. I got another idea of using saturated NaCl water solution to wash. Do you think it can work?

No, you will loose some of your product in the brine.