YT2095
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an Amine / Iodine concern
when wanting to make an Amine say on a Phenol or benzene ring, it`s usual to use a Halogen 1`st and then the Ammonia soln to displace that.
or at least so I understand it from books.
the problem is that Not everyone want`s to mess with Chlorine or Bromine (I certainly don`t) but I DO have elemental Iodine, which is much nicer to
handle.
however the problem comes with the addition of Ammoium ion to this, I don`t want NI3 forming!
is there a way around this, or have I writen myself into a corner? so to speak.
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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Nicodem
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| Quote: | | when wanting to make an Amine say on a Phenol or benzene ring, it`s usual to use a Halogen 1`st and then the Ammonia soln to displace that.
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No, it is not usual to use such a route. Aromatic nucleophilic substitutions are anything but easy (except for a few exceptions). I would even say it
is highly unusual to use nucleophilic aromatic substitution or the Cu catalyzed analogous but mechanisticaly different reaction, the Ullman reaction to prepare anilines. It is also quite difficult to prepare an aniline with ammonia by either of the two reactions since the
aniline can react as a nucleophile as well. I heard that it is (or was) used industrially to prepare aniline from chlorobenzene with a large excess of
ammonia in an autoclave (but can you heat an autoclave to 350°C at home ).
| Quote: | | however the problem comes with the addition of Ammoium ion to this, I don`t want NI3 forming! |
Ammonium ions are not nucleophilic, you need ammonia.
And I don't understand what you mean. Before you were talking about halogenating benzene or phenol and trying to do a nucleophilic aromatic
substitution. So, for example, you would have to prepare iodobenzene first (I2 by itself is not enough for that anyway). Then you would,
hypotheticaly, react iodobenzene with ammonia. Of course there would be no reaction, but even if there would be, there is no way to form NI3*NH3.
And the leaving group tendency in normal nucleophilic aromatic substitutions is F>>Br>Cl>>I (the inverse of the SN2 substitutions). So
iodobenzene of iodophenols are not apropriate (unless for the Ullman reaction conditions where the bromo- and iodo- arenes are best).
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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YT2095
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so you`re trying to tell me that Phenol + 3Br2 in water will not make 2,4,6 tribromophenol?
or any other Halogen for that matter won`t make the coresponding 2,4,6 halophenol?
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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Nicodem
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Huh, what that has to do with your original question and my reply?
Yes, the phenol can be brominated to 2,4,6-tribromophenol with Br2.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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YT2095
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read my 1`st post again then *sigh*
you will see I clearly stated that Halogenation is first, and then went on to say that I used I2 instead.
I then follow on to say that Ammonia is used to Displave the Halogen to leave the Amine blah blah blah...
can you Not understand my question I asked, or are you SO hung up on nitpicking all the time that you can`t get past it long enough to actualy Read?
This is a Bloody good website and a great place to learn and ask things, why must you try and spoil this?
You can Dim someones elses Bulb, but it will Never make Yours any brighter!
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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Nicodem
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Sorry if you felt like I was trying to put your ideas down. Sincerely, that was not my intention. I just wanted to explain you where you are wrong and
why. I now see why you feel offended. I should have not told that your ideas would not work. You are too sure about them and don’t have any doubts
that only an experiment can show you how things work in the real world. You are right, I’m s very inclined in nitpicking and I can’t help my self
about it – it’s a professional deformation since I’m a scientist. I understand how annoying that can be if this helps you. So sorry again.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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unionised
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Well, I read it.
It's not very common to use the reaction of an aryl halide with ammonia to form an amine because, generally it doesn't work and/ or is very slow.
You can certainly iodinate some aromatics with iodine, but it doesn't work for all of them. For example, it doesn't work with benzene.
Conversion of the aryl halide to an amine might work (on a good day with a following wind), but not if you add an ammonium salt- you would need to
add ammonia.
The fact that iodine reacts with ammonia is a total red herring. The iodine isn't there anymore because it reacted with the aromatic ring in the first
place. (except of course, in most cases it won't have because iodine isn't very active.
In short, if you take (for example) benzene and react it with iodine nothing will happen. If you do somehow get iodobenzene (IIRC the iodination can
be done in the presence of nitric acid) and react it with ammonia, nothing will happen. Since iodobezene isn't iodine it doesn't give NI3 with
ammonia.
It's poor practice to leave excess of the previous reagent in with the product when you conduct the next stage of a synthetic sequence for exaclty the
sort of reason you are giving.
It's hardly nitpicking to point out that
1 your first assertion simply isn't true.
2 You can generalise halogenation to include iodination (it only works for very active aromatics).
3 You usually ought to purify the product from the first stage of a synthesis before going on to the second.
And I, for one, hope that the process of teaching people about their mistakes doesn't dim anyones bulb.
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YT2095
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I`m aware that Special conditions are needed for Benzene alone, that indeed was a mistake on my part to enter in the 1`st post, I appologise.
when I said the Ammonium Ion, I meant as the Ammoi as stated in the 1`st post since that`s the part that makes the change-over sustitution with the
halogen.
I am using Very willing/reactive compounds with the I2 namely Hydoquinone and also Pyrocatechol, both show signs of reaction in a very pleasing way (I
don`t have "Black stuff" as a product this time).
and yes, I plan on purifying before ammonia reaction, however...
this book recommends adding the ammonia in Excess, and since that`s the case, where will the I2 go when it leaves the ring?
right back into the Ammonia in excess I would think, and then form compounds I have no wish to be around!
the last thing I want is to be looking at my Catecholamine and have the ba$tard blow up in my face!
EDIT: and yes, I`m here to Learn and to share, but there are Ways and Ways to do this! 
[Edited on 10-7-2006 by YT2095]
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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garage chemist
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Substitution of an aryl halide with ammonia does not work as you'd want it to.
The resulting aniline reacts with more aryl halide far easier than ammonia, and your main products will be the diphenylamine and the triphenylamine.
Don't follow this route, as it will be a waste of time.
Also, if you react an aryl halide with ammonia, there's no way on earth it could ever form NI3. Look at the oxidation number of the iodine before and
after the reaction. NI3 only forms with elemental iodine, which has oxidation number zero.
You have to nitrate your hydroquinone or pyrocatechol and then reduce the nitro compound with iron/HCl. THIS is the standard way to aromatic amines.
You just have to find a working procedure for nitration.
Throwing the stuff into a H2SO4/nitrate mix is clearly the wrong way, as you've already seen.
If you throw ordinary phenol into H2SO4/nitrate mix you get black stuff as well! Phenols, and even more diphenols like your hydroquinone/catechol are
very sensitive to oxidation, leading to black stuff.
However, mononitrophenol can be produced by nitration of phenol directly. It's a matter of the reaction conditions.
The exactly same applies to your diphenols.
For phenol, 40% aqueous nitric acid is used for nitration, and your diphenols will need roughly same conditions.
Go get the Organikum (go to your university library if you don't want to buy the book), it has the complete description of the process.
You always need a synthesis procedure if you want to make something.
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unionised
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OK, the reaction doesn't work with aryl halides (usually) but for alkyl halides the reaction is RI + 2NH3-->RNH2 +NH4I
No NI3.
For what it's worth I would be quite plased if I could get C6H6 ---> C6H5I ---> C6H5NH2 to work, but it won't. (Well, it might via oxidative
iodination, a grignard reaction, addition of CO2, conversion to an acid chloride, turning that to an amide then hoping to blazes that the Hoffmann
degradation works. On second thoughts, I might just buy the stuff)
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