Paracetamol Hydrolysis question (4-aminophenol)

Athiril · Feb 9, 2010

Not after a parodinal formula.

I was wondering, how many mol to how many mol it takes for paracetamol to convert to 4-aminophenol, using potassium hydroxide.

edit: and the resulting amount of 4-aminophenol.

gainer · Feb 9, 2010

It takes 151.17 grams of paracetamol (Tylenol) to make 109.13 grams of 4-aminophenol.

Athiril · Feb 9, 2010

The important part is how much potassium hydroxide does that take? Is it 1 mol to 1 mol?

If you get less 4-aminophenol than the weight of paracetamol and hydroxide together.. what are the byproducts?

Alan Johnson · Feb 9, 2010

If you use paracetamol (insoluble) to make p-aminophenol (insoluble) how do you know the reaction has gone to completion and the result is not a mixture of the two?To get round this I make the aminophenolate which is soluble.I use sodium not potassium but the equation can be converted by replacing Na=23 by K=39.The by-products are sodium acetate and water.

C8H9NO2......+.....2NaOH...........->...C6H6NaNO....+C2H3NaO2.....+H2O
Paracetamol..Sodium Hydroxide....->.Sodium Aminophenolate...+...+..
151.17..................80...............->....131.12.......

Kirk Keyes · Feb 9, 2010

You probably want an excess of NaOH there too to drive the reaction and keep the pH up for the hydrolysis...

Athiril · Nov 15, 2010

I wanted to come back to this.. what about hydrolysis with HCl?

I want to prepare the dry chemical form.

Gerald C Koch · Nov 16, 2010

Athiril said:
I wanted to come back to this.. what about hydrolysis with HCl?

I want to prepare the dry chemical form.

Do you wish to prepare p-aminophenol or to just prepare a pure form of acetaminophen without the binder?

If it is the former then sulfuric acid would be a better choice since the mixture must be refluxed for about an hour and HCl will produce acid fumes while sulfuric acid will not.

Athiril · Nov 16, 2010

I find it hard to get H2SO4 here, but now I live a suburb of a capital city I'll give it another go.

I want to prepare dry aminophenol.

Paracetamol without the binder I can do... filter with methylated spirits and dry that methylated spirits of, real pain in the arse to then mortal and pestle it into powder, but it works, but it degrades with reasonably logn exposure to air, the powder itself will discolor over time.

Although I did keep it out on a piece of paper rather than a jar or container.

Wouldn't hyrdolysis with HCl make the aminophenol-hydrochloride form?

Athiril · Nov 16, 2010

I was just thinking I should be able to do the hydrolysis of paracetamol with NaOH, then precipitate it with HCl, filter and wash with water.. but then what form do I end up with?

Gerald C Koch · Nov 16, 2010

The hydrolysis works better in acid solution. The mixture must be kept close to the boiling point for about an hour and hydrochloric acid generates some very nasty fumes under these conditions. When the hydrolysis is completed the acid is neutralized with sodium carbonate and pap free base precipitates. This can be converted to the HCl if desired. Add a small amount of sodium sulfite to the carbonate solution to prevent oxidation. I would suggest using a 1M solution of sulfuric acid.

For sulfuric acid can you obtain battery acid as this is dilute sulfuric acid? Should be available in auto parts stores.

Athiril · Nov 16, 2010

I'm familiar with working with HCl, so thats not a bother.

As far as Sulphuric Acid goes from Auto Shops.. doubt it, most of them (we tend to only have chains around for auto markets too) sell it for 5 cents for a litre, but store policy only sells it to you with the purchase of a motorcycle battery, and 1 per customer.

I might be able to find it other places, I'll have to look. But HCl is really easy to get in any quantity, and cheap.

So the "It takes 151.17 grams of paracetamol (Tylenol) to make 109.13 grams of 4-aminophenol" applies to the free-base.. but the free-base, is it unstable for storage?

Was just looking over
http://msds.chem.ox.ac.uk/AM/4-aminophenol.html
and
http://msds.chem.ox.ac.uk/AM/4-aminophenol_hydrochloride.html

Aminophenol "Stable, though may discolour in air. Incompatible with acids, chloroformates, strong oxidizing agents. "

Aminophenol HCl "Stable, but hygroscopic, air and light sensitive. Incompatible with strong oxidizing agents. "

Either case Iw ould prefer to store the HCl salt.

john_s · Nov 17, 2010

4-aminophenol is a common chemical. You could buy some. I get mine from Merck in Melbourne.

Athiril · Nov 17, 2010

How much is it?

Eg:

I already had a registered login with merck ages ago, but once I login, requests for pricing cart disappears, as does the link to make a request for pricing in all chems.

So I cant even get a quote from merck, let alone order, I presume it will be expensive.

I'd still prefer to prepare my own dry HCl salt of aminophenol.

Alan Johnson · Nov 18, 2010

Adding dilute HCl to a solution of aminophenolate produces a precipitate at around neutral pH which is probably p-aminophenol.This is probably the easiest way to make it.IMO the whole process is hazardous and non-chemists should not try it.

john_s · Nov 18, 2010

Athiril said:
How much is it?

Eg:

I already had a registered login with merck ages ago, but once I login, requests for pricing cart disappears, as does the link to make a request for pricing in all chems.

So I cant even get a quote from merck, let alone order, I presume it will be expensive.

I'd still prefer to prepare my own dry HCl salt of aminophenol.

I just telephoned them. I don't remember the price. Whether or not it's expensive depends on quantities you can buy, quantities you need etc. I remember it being not very expensive. But I haven't used a lot of it, and it might not keep as well as some other dev agents.

Athiril · Nov 18, 2010

Alan Johnson said:
Adding dilute HCl to a solution of aminophenolate produces a precipitate at around neutral pH which is probably p-aminophenol.This is probably the easiest way to make it.IMO the whole process is hazardous and non-chemists should not try it.

Well I have fine enough pippettes, but a probably is kind of... well.. hmm.

I found this which may be useful to some others as well
http://books.google.com.au/books?id...ol hydrochloride&pg=PA377#v=onepage&q&f=false

Paracetamol Hydrolysis question (4-aminophenol)

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