panziandi
Hazard to Others
Posts: 490
Registered: 3-10-2006
Location: UK
Member Is Offline
Mood: Bored
|
|
Old aniline HCl?
A few years back I purchased some "Aniline HCl" off a guy un the UK. Now this stuff arrived in a HDPE bottle i opened it up to find it filled with a
dark green crystaline powder. Now on close inspection there is a chrome green crystaline powder with the odd larger flat colourless crystal mixed in.
Now I never used it and put it away. I had totally forgotten about it until I needed some aniline. I thought I'd buy some fresh then thought "wait
don't I have some Aniline HCl?" so I find this jar after many years and I investigate the contents. It dissolves slowly in water to yield a green
solution addition of hydroxide makes it all dissolve and an oily dark liquid separates on top of the hydroxide and a peculair "organic" smell is
noticeable, not amine-like at all.
Does anybody have any idea WTF I have got? I thought maybe a phenylhydrazine salt? perhaps some azo compound? I'm happy to give people a sample if
anyone can identify it! In the mean time i'll shop around for proper freebase aniline!
|
|
|
matei
Hazard to Others
Posts: 205
Registered: 16-9-2006
Member Is Offline
Mood: No Mood
|
|
You should try to distill some of the liquid. My guess is it's aniline. Aromatic amines aren't very stable in time, they tend to react with the CO2
from the atmosphere. Also, pure aniline doesn't have an "amine-like" smell (assuming "amine-like" means ammonia-like, which is what low molecular
weight aliphatic primary amines smell).
[Edited on 19-7-2008 by matei]
|
|
|
ScienceSquirrel
International Hazard
Posts: 1863
Registered: 18-6-2008
Location: Brittany
Member Is Offline
Mood: Dogs are pets but cats are little furry humans with four feet and self determination! 
|
|
I would say that your material is quite pure.
Aniline and its salts rapidly darken in the presence of light and oxygen but the impurities formed are less than a few per cent.
What do you want to do with it?
Aniline does not have an amine smell at all to me. Aniline is quite insoluble in water so separating out on addition of hydroxide is also quite
reasonable.
A definitive test is adding a solution of potassium hydroxide to the amine salt with a few drops of chloroform. Phenyl isocyanate is formed, it
pongs...
[Edited on 20-7-2008 by ScienceSquirrel]
|
|
|
Ritter
Hazard to Others
Posts: 370
Registered: 20-6-2008
Location: Earth
Member Is Offline
Mood: Curious
|
|
| Quote: | Originally posted by matei
You should try to distill some of the liquid. My guess is it's aniline. Aromatic amines aren't very stable in time, they tend to react with the CO2
from the atmosphere. Also, pure aniline doesn't have an "amine-like" smell (assuming "amine-like" means ammonia-like, which is what low molecular
weight aliphatic primary amines smell).
[Edited on 19-7-2008 by matei] |
You can't distill amine salts. They usually will decompose. It's usual to convert them into the free base, then distill those.
Ritter
=============================
\"The production of too many useful things results in too many useless people.\"
Karl Marx
|
|
|
S.C. Wack
bibliomaster
Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
Member Is Offline
Mood: Enhanced
|
|
Purify the suspect cpd. in the usual way for aniline and see what happens.
| Quote: | Originally posted by ScienceSquirrel
Aniline is quite insoluble in water |
Merck copy/paste: One gram dissolves in 28.6 ml water
| Quote: | Originally posted by Ritter
You can't distill amine salts. |
And neither matei nor anyone else was proposing to do so.
If you take a few milligrams of an aniline salt and dissolve it in several ml of tap water with several milligrams of NaOH or KOH, and add to this a
few drops of a filtered solution made from several milligrams of calcium hypochlorite pool sanitizer dissolved in several ml of tap water, or other
hypochlorite bleach, you turn water into wine within seconds - the solution is purple by reflected and red by transmitted light. Probably not a good
specific test just for aniline itself, especially if other cpds. may be present which also give highly colored oxidation products, but it is quite a
sensitive one.
|
|
|
panziandi
Hazard to Others
Posts: 490
Registered: 3-10-2006
Location: UK
Member Is Offline
Mood: Bored
|
|
Thanks for all the replies!
Ok I put 13g of the aniline HCl and 2.5g of NaOH in a flask added minimum water it heated alot (obviously) dark oily tarry liquid floated ontop clings
to glass. Added xylene (wash bottle at hand) dissolved something as the layer turned purple/red. The aqueous layer was slightly cloudy and a green (?)
layer between the xylene and water. In hind sight I should have tried ether as that dissolves aniline well and is regularly employed to extract
dissolved aniline in steam distilates.
I wanted the aniline to make iodobenzene from so clean aniline is preferable since these impurities are probably going to be a problem to remove from
the iodobenzene (speculation). I suppose a steam disilation from hydroxide is needed really. Should I try a Sn/HCl reduction first though? Any
thoughts?
|
|
|
UnintentionalChaos
International Hazard
Posts: 1454
Registered: 9-12-2006
Location: Mars
Member Is Offline
Mood: Nucleophilic
|
|
You'll almost always end up with black, awful looking product when working with aniline. There was a prep posted quite a while back about iodobenzene
from aniline. The product was....a black oil and required distillation, yet provided high yield.
EDIT: I can't seem to find it...this was over a year ago. Perhaps I was just remembering Garage Chemist's references to his own preparation...anyway
here's him quoted
"I ran this reaction without the slightest problems, and isolated a good yield of iodobenzene.
The reaction (benzene diazonium chloride + KI) needs to be left to stand for about 24 hours, it doesn't hurt if you leave it to stand even longer.
Then it is slowly warmed to 50°C and held there until the nitrogen evolution has ceased entirely.
The iodobenzene separates as a black very heavy oil. If your batch was small it might be hard to see. Tilt the beaker, or decant most of the
supernatant."
[Edited on 7-21-08 by UnintentionalChaos]
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
|
|
|
Klute
International Hazard
Posts: 1378
Registered: 18-10-2006
Location: France
Member Is Offline
Mood: No Mood
|
|
I would suggest dissolving your salt in dH2O, washing the solution with an adequate solvent, then freebasing and extarcting with a low boiling
solvent. Remove your solvent and it should be pur enough for a diazotation.
A good test to determine priamry, seconday and tertiary amine with easily obtainable materials is the nitrous acid test (basicly performing a diazotation).
\"You can battle with a demon, you can embrace a demon; what the hell can you do with a fucking spiritual computer?\"
-Alice Parr
|
|
|
ScienceSquirrel
International Hazard
Posts: 1863
Registered: 18-6-2008
Location: Brittany
Member Is Offline
Mood: Dogs are pets but cats are little furry humans with four feet and self determination!
|
|
I would dissolve the aniline HCl in water.
Extract with a solvent to remove tars etc
Add NaOH and extract the aniline into solvent
Extract the solvent with dilute H2SO4
Cool and diazotise
React with KI and then extract and distill the dark oil.
|
|
|
panziandi
Hazard to Others
Posts: 490
Registered: 3-10-2006
Location: UK
Member Is Offline
Mood: Bored
|
|
Thanks, I didn't think of attempting washings! It appears form a quick trial that washing an aqueous solution of the crude aniline HCl with ethyl
acetate results in the removal of the green contaminating chemical, giving a clear colourless aqueous solution. I'm unsure if free-basing and solvent
extraction of the aniline then washing out of the solvent with acid are necessary steps, just seems like I'd be back tracking and risking oxidation of
the free aniline which is more unstable than the salt?!
|
|
|
ScienceSquirrel
International Hazard
Posts: 1863
Registered: 18-6-2008
Location: Brittany
Member Is Offline
Mood: Dogs are pets but cats are little furry humans with four feet and self determination!
|
|
It depends on what you want to do next?
You have a clean solution of aniline hydrochloride in water.
|
|
|
panziandi
Hazard to Others
Posts: 490
Registered: 3-10-2006
Location: UK
Member Is Offline
Mood: Bored
|
|
I want to diazotise and react with KI to yield iodobenzene.
|
|
|
ScienceSquirrel
International Hazard
Posts: 1863
Registered: 18-6-2008
Location: Brittany
Member Is Offline
Mood: Dogs are pets but cats are little furry humans with four feet and self determination!
|
|
I would take a look at the preparation you are intending to use and adapt it to use aniline hydrochloride instead of aniline as the starting material.
Pretty easy really 
|
|
|
UnintentionalChaos
International Hazard
Posts: 1454
Registered: 9-12-2006
Location: Mars
Member Is Offline
Mood: Nucleophilic
|
|
You'd need to use HCl (HCl + NaNO2 in the cold) to diazotize anyway so you'd make the salt as it is.
[Edited on 7-22-08 by UnintentionalChaos]
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
