Sciencemadness Discussion Board

Hydrolysis and decarboxylation of nitriles with Phosphoric acid. Can't find any experimental data.

Crypto - 9-12-2014 at 06:34

I can't find any experimental data on the hydrolysis and subsequent decarboxylation of nitriles with 85% phosphoric acid. All I can find with google is that the reaction proceeds in about 150-160 C temperature range. I'm interested what is the time of the reaction, the necessary amount of acid and it's mechanism.

Aren't diluted acids usualy used for hydrolysis reactions?

forgottenpassword - 9-12-2014 at 07:03

If you are sure of the details, you have enough information to perform the reaction: Mix an excess of 85% phosphoric acid with your nitrile, and heat to 150-160C. Using an excess of phosphoric acid won't harm anything! Simply monitor its progress with TLC.

Personally I have never heard of the reaction. What is the product of decarboxylating carboxylic acids with phosphoric acid?

[Edited on 9-12-2014 by forgottenpassword]

Chemosynthesis - 9-12-2014 at 16:14

Quote: Originally posted by forgottenpassword  
Personally I have never heard of the reaction. What is the product of decarboxylating carboxylic acids with phosphoric acid?

Good question. What is your substrate?

I have seen acid catalyzed nitrile hydrolysis (usually with a stronger acid such as sulfuric, which can also decarboxylate some subtrates).

morganbw - 10-12-2014 at 04:00

Quote: Originally posted by forgottenpassword  
If you are sure of the details, you have enough information to perform the reaction: Mix an excess of 85% phosphoric acid with your nitrile, and heat to 150-160C. Using an excess of phosphoric acid won't harm anything! Simply monitor its progress with TLC.

Personally I have never heard of the reaction. What is the product of decarboxylating carboxylic acids with phosphoric acid?

[Edited on 9-12-2014 by forgottenpassword]


Look @ procedure B on this page and it may give a clue
I think their is a Russian prep that uses H3PO4 instead of H2SO4, this may not be the actual target, but I wonder?
prep=cv2p0389http://www.orgsyn.org/demo.aspx?prep=cv2p0389

[Edited on 10-12-2014 by morganbw]

forgottenpassword - 10-12-2014 at 04:45

He's talking about nitrileS in general. That would be a specific case where decarboxylation is facile, but I think that he had a general reaction of nitriles in mind.

Edit:
Actually, having looked at his previous posts, you're absolutely right! :D This guy isn't interested in nitriles, he's interested in methamphetamines! Maybe I've jumped to the wrong conclusion: he's interested in methylamine production, nitrostyrene reduction, and reductive amination reactions using Al/Hg! There, that's more accurate.

Here was I thinking he knew of some obscure general decarboxylation reaction using phosphoric acid! Well, your link ought to be helpful to him, I suppose. Sulfuric acid it is! You'll have your meth cook under way in no time at all, Crypto! Public confessional done as well. Are you a Catholic?! Many Catholics come on here to make their intentions perfectly clear to anyone who wants to know. Public confessional is VERY important!



[Edited on 10-12-2014 by forgottenpassword]

morganbw - 11-12-2014 at 07:10

Quote: Originally posted by forgottenpassword  
He's talking about nitrileS in general. That would be a specific case where decarboxylation is facile, but I think that he had a general reaction of nitriles in mind.

Edit:
Actually, having looked at his previous posts, you're absolutely right! :D This guy isn't interested in nitriles, he's interested in methamphetamines! Maybe I've jumped to the wrong conclusion: he's interested in methylamine production, nitrostyrene reduction, and reductive amination reactions using Al/Hg! There, that's more accurate.

Here was I thinking he knew of some obscure general decarboxylation reaction using phosphoric acid! Well, your link ought to be helpful to him, I suppose. Sulfuric acid it is! You'll have your meth cook under way in no time at all, Crypto! Public confessional done as well. Are you a Catholic?! Many Catholics come on here to make their intentions perfectly clear to anyone who wants to know. Public confessional is VERY important!



[Edited on 10-12-2014 by forgottenpassword]


You are a bit spicy:)

My reply was due to his previous posting history. It also wasn't meant to be mean, merely to wake him up to the reality that certain paths, if taken to their conclusion can destroy your life.
I may be wrong, but I think that even an illusion of conspiring to manufacture can eff your life up.

I did a google search using "Hydrolysis and decarboxylation of nitriles with Phosphoric acid",
and it lead to this link Bulletin on Narcotics: Science in Drug Control - the Role of Laboratory and ...

To add clarity to what this pointed out, and to show off my searching skills, I searched google again using this
" a-phenylacetoacetonitrile site:www.orgsyn.org/"

This took me to the synth.
By the way the H3PO4 purportedly offers an increased yield.

If I could see this, then it is a given that the police/DEA/some bored forensic chemist etc... did as well.

And for your pleasure I am not Catholic


Crypto - 11-12-2014 at 08:20

Well if you would read "Phosphoric Acid: Purification, Uses, Technology, and Economics" by Rodney Gilmour, you would notice the paragraph on page 198:

"The hydrolysis of nitriles to carboxylic acids with orthophosphoric acid is classic as is reductive decyanation with polyphosphoric acid..."

Now something that is suppose to be a classic should be well covered. Unfortunately I can't find much information about it.

There is a mention of it in "The Chemistry of Heterocyclic Compounds, Condensed Imidazoles, 5-5 Ring Systems" edited by P. N. Preston:

"...in 90% phosphoric acid at 160 the latter reaction occurs in addition to hydrolysis of the nitrile and ensuing decarboxylation..."

I also saw it mentioned in some polish chemical journal (translated to english) but I can't find it right now. The temperature given there was higher thou, around 200 C and anhydrous acid was used.


As for my posting history I don't really understand what is so dodgy about it? Hundreds of users from this forum, including some of the well known and respected here have procured methylamine. You can read various threads about it. For a hobbyist like me who wanted to try the Al/Hg reduction there is no better substrate than nitromethane. Can be bought cheap and easyly, plus there is a lot of posts on it, writen by other users. I just could compare results with others... The nitrostyrene I was reducing lead to phenethylamine, a legal and pharmacologically inactive compound.

I also have to point out that in many cases the first results google gives are related to clandestine chemistry, even when that is not what one is looking for.

morganbw - 11-12-2014 at 08:35

My apology Crypto.
I am glad I was mistaken.

Chemosynthesis - 11-12-2014 at 12:06

Quote: Originally posted by Crypto  
Well if you would read "Phosphoric Acid: Purification, Uses, Technology, and Economics" by Rodney Gilmour, you would notice the paragraph on page 198:

"The hydrolysis of nitriles to carboxylic acids with orthophosphoric acid is classic as is reductive decyanation with polyphosphoric acid..."

Now something that is suppose to be a classic should be well covered. Unfortunately I can't find much information about it.

Being a classic, much of the literature is ancient and not always in English (as you see with the Polish article). Pretty sure I have some examples dating back to Justus Liebigs Annalen der Chemie in a filing cabinet. I'll have to check.
Quote:
There is a mention of it in "The Chemistry of Heterocyclic Compounds, Condensed Imidazoles, 5-5 Ring Systems" edited by P. N. Preston:

"...in 90% phosphoric acid at 160 the latter reaction occurs in addition to hydrolysis of the nitrile and ensuing decarboxylation..."

What is this substrate?

Crypto - 11-12-2014 at 12:49
Quote:

My apology Crypto.



I didn't feel offended but you're welcome.
Quote:

What is this substrate?



It referred to three nitrile derivatives of 1H-PYRROLO(1,2-a)IMIDAZOLE that I don't really know how to name :)

[Edited on 11-12-2014 by Crypto]

[Edited on 11-12-2014 by Crypto]

Chemosynthesis - 11-12-2014 at 13:00

Quote: Originally posted by Crypto  


It referred to three nitrile derivatives of 1H-PYRROLO(1,2-a)IMIDAZOLE that I don't really know how to name :)

Was the nitrile hydrolyzed to a beta keto acid? These are particularly easy to decarboxylate (if you aren't yet aware), and could presumable by made from an SN2 reaction after alpha halogenation of a ketone.

kmno4 - 11-12-2014 at 14:57


Long time ago I made such an experiment with ketonitrile (mentioned earlier in OS procedure).
With H2SO4(aq) result were very bad, SO2 + brown impure product (-> WC).
With ~90% H3PO4 results were very good, with clean, light yellow product. When CO2 liberating stops, reaction is finished.
90% H3PO4 was made from 75% acid and crappy P2O5 (as much as the correct bp for ~90% acid was obtained)

Crypto - 11-12-2014 at 15:36

Quote:

Long time ago I made such an experiment with ketonitrile (mentioned earlier in OS procedure).
With H2SO4(aq) result were very bad, SO2 + brown impure product (-> WC).
With ~90% H3PO4 results were very good, with clean, light yellow product. When CO2 liberating stops, reaction is finished.
90% H3PO4 was made from 75% acid and crappy P2O5 (as much as the correct bp for ~90% acid was obtained)


Do you remember the molar ratio of acid to substrate you used?
Was the reaction held at reflux?


Apparently a mixture of glacial acetic acid with a mineral acid works well. I saw it mentioned in a patent. I think it was 1:3 for GAA to concentrated hydrochloric acid and 1:1:1 for H2SO4, GAA and water.

[Edited on 11-12-2014 by Crypto]