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Rabodon
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Quote: Originally posted by bbartlog  | | What procedure are you trying to execute? There are no reducing agents in the chemicals you list, only catalysts and hydrogen donors, and furthermore
potassium formate seems like it would be needlessly alkaline, but without any mention of substrate, conditions etc. I can't tell whether you are
omitting details or actually trying to do something senseless. |
I didn't ask for explicit help for my reductions, I've only asked if someone here had success with it.
PS: As potassium formiate is generally used with excess HCOOH I thought the alkaline character doesn't matter, or did I make a bad mistake here?
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zed
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Nope. Pd and Pt, are very easy to obtain. E-bay
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CuReUS
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zed
even if they are easy to obtain,they arent that easy to work with
as i take it ,you must make a pd catalyst bed ,pass H2 over that,the stream of gas should be steady,it has to be purified(dust,foreign
objects kill the catalyst),and having a H2 cylinder or a generator is like sitting on a time bomb
taking a beaker,dumping in your nitro compound and HCOOH,and adding Zn in portions seems much easier,and it is as i have already done it ,but with
Zn/HCl (may be not faster but wayyyyyyyy easier)
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CuReUS
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| Quote: Originally posted by Rabodon |
It's my empirical data.
HCl a stronger proton donor for sure but in my experience simply also causes more side products.worse soloubility of reactants due the water from the
aq. HCl, the reactivity of ZnCl2, .... |
i agree on the solubility factor.i had mixed 10ml HCl and 10ml water and put that into a beaker with the dinitro compound,i didn't put any alcohol or
any other organic solvent at all,to prevent side reactions
as a result ,initially the solubility was very bad,but as more and more dinitro got converted to the diamino, and the diamino formed salt with the
HCl ,the solubility increased until everthing had dissolved
| Quote: | | For me HCOOH instead of HCl worked always better, yielding often perfectly clear and colorless amine straight after simple acid/base workup while the
HCl way always caused slightly to much lower yields and products which always cotained more or less visible goo, for some reactions sometimes very
much of it. |
i didnt get a colorless solution at all
my starting compound,2,4-dinitrophenol made the solution color yellow and after 45 minutes( after most of the dinitro had got reduced)the color was
tan yellow like light tea
but when i filtered the solution,the filterate was exactly according to literature-slightly pink
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zed
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On the contrary, Pt and Pd are easy to work with. I prefer Pt, because I think Pd is now vastly overpriced.
I used to like to produce Pt catalysts by the action of NaBH4 on Chloroplatinic Acid, in Ethanol.
Makes a very active catalyst, and it requires very little NaBH4.
Chloroplatinic acid can be produced by the action of Aqua Regia on Platinum. But, it is also quite possible, that electrolysis of Platinum in
Hydrochloric acid will do the trick.
Catalyst bed? Not usually. Usually just a sealed flask, with Pt, H2, solvent and a stir bar.
Oh well, to each their own.
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CuReUS
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| Quote: Originally posted by zed | | But, it is also quite possible, that electrolysis of Platinum in Hydrochloric acid will do the trick. |
really,i thought Pt was one of the most inert metals,this is interesting
| Quote: | | Usually just a sealed flask, with Pt, H2, solvent and a stir bar. |
sealed flask with gaseous products,a chemist's version of a time bomb dont you think ,with NaBH4 around
but you should read this book(pg 31) under "Appendix 2 Watched Chemicals,
it lists palladium black as a watched chemical
Attachment: Nimble.pdf (251kB)
This file has been downloaded 721 times
[Edited on 1-10-2014 by CuReUS]
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zed
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Platinum is pretty inert, but not to elemental chlorine.
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CuReUS
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so does that mean gold is the most inert metal?
many books list gold above platinum in the reactivity or the electrochemical series
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violet sin
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iridium, wiki:
http://en.wikipedia.org/wiki/Iridium
"is the most corrosion-resistant metal, even at temperatures as high as 2000 °C"
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zed
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I would expect gold also to react with elemental Chlorine.
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CuReUS
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that's why they use Pt/Ir alloy for making the standard weight of 1 kg at the SI units office at paris
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CuReUS
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is elemental chlorine even more reactive than a chlorine free radicle?
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zed
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Don't know. Just know that precious metals can be leached from crushed ores, via elemental Halogens. Some techniques call for the generation of
those Halogens, via the action of Oxone (pool shock) on Halogen Salts. Might be a spendy way to go. But, you can bet your ass that the manufacturers
of Oxone, think it is a mighty fine idea.
As for the practicality of dissolving Pt in HCl with the assistance of an electrical current, unless the literature contains a good procedure, I'd
have to experiment.
Maybe it is workable, maybe not.
Nice article posted elsewhere on this board. http://www.technology.matthey.com/article/57/4/289-296/
[Edited on 4-10-2014 by zed]
[Edited on 4-10-2014 by zed]
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CuReUS
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btw ,why is fe or Sn preferred over Zn for reducing agent although Zn lies above both of them in the electrochemical series
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Nicodem
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| Quote: Originally posted by CuReUS | | btw ,why is fe or Sn preferred over Zn for reducing agent although Zn lies above both of them in the electrochemical series |
Why would the electrochemical series be that relevant for the reduction of nitro compounds? The electron transfer from the metal surface to a neutral
organic compound is not that similar to the electron transfer from the surface to a metal cation, hydronium ion, or water. There are more important
factors at play.
| Quote: Originally posted by CuReUS | as i take it ,you must make a pd catalyst bed ,pass H2 over that,the stream of gas should be steady,it has to be purified(dust,foreign
objects kill the catalyst),and having a H2 cylinder or a generator is like sitting on a time bomb
taking a beaker,dumping in your nitro compound and HCOOH,and adding Zn in portions seems much easier,and it is as i have already done it ,but with
Zn/HCl (may be not faster but wayyyyyyyy easier) |
It is quite obvious from your prejudices that you have never done a hydrogenation in your life. Comparing something as simple and straightforward as a
hydrogenation over a balloon with something as tedious as a metal dissolving reaction on a substrate that gives a product so difficult to isolate is
totally unreasonable. With a metal dissolving reaction, you will most likely consume most of your material just to develop a working isolation
procedure, while a hydrogenation would give you near quantitative yields and no fuss whatsoever with any kind of development. For an amateur chemist
with limited resources and equipment, hydrogenation is probably the only useful method on such a substrate.
…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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CuReUS
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| Quote: | | Quote: Originally posted by Nicodem | | Quote: Originally posted by CuReUS | btw ,why is fe or Sn preferred over Zn for reducing agent although Zn lies above both of them in the electrochemical series
Why would the electrochemical series be that relevant for the reduction of nitro compounds? The electron transfer from the metal surface to a neutral
organic compound is not that similar to the electron transfer from the surface to a metal cation, hydronium ion, or water. There are more important
factors at play. |
yes ,now i realize that i was a fool to come to such a silly conclusion.
it would be very helpful if you could tell more about the other factors
| Quote: | | It is quite obvious from your prejudices that you have never done a hydrogenation in your life |
yes i have
never done it and have no right to come to such stupid conclusions,i am terribly sorry [qoute]Comparing something as simple and straightforward as a hydrogenation over a balloon |
so in Pd
hydrogenation what is the source of hydrogen.is it from a cylinder?. | Quote: | | With a metal dissolving reaction, you will most likely consume most of your material just to develop a working isolation procedure
|
that is true ,considering the 3:1 ratio of Zn-nitro and the separation of ZnCl2 from the mixture
would be difficult(as you could not displace it with some easily available metal which is also more elctropositive than Zn)although idont understand
this logic
suppose you used Fe and you displaced the FeCl3 formed with Sn or Al foil,how would you separate the Sn/Al from the mixture now.do they
form some insoluble salt that you can just filter off.
also could we add an excess of ZnCl2 to the mixture to salt out the reduced organic compound from the aqueous layer(if only HCl is used as
i did)or the HCl+ethanol layer(but rabodon mentioned on page 1 that HCl+ethanol could give some side products and goo formation)
i have salted out acetone and IPA(which are so soluble in water) so why cant the same logic be applied here?
also i have to confess that i was wrong in thinking that H2S could only reduce one of the nitro groups in the dinitro as crowjford has used
it to reduce tetranitro to tetraamine(see page 1) .
although you say that Pd hydrogenation is the best bet,i am not capable of doing it just yet because i still have a lot to learn about the procedure
and getting Pd is not possible
so i am thinking of doing the sulphide reduction for my next experiment(reducing 4 -nitrosophenol to 4-aminophenol for making paracetamol)
so while doing the sulphide reduction,do we mix the sulphide salt(Na22) with the nitroso and acidify the solution?
PS- nicodem,i initially thought that you were a rude know-it-all type of person but after reading this previous post i know that you are far from that.you saved that guy's life ,if you hadn't pointed out polyammonium sulphides corrode steel ,he
would have been dead by now.although people may think you are rude,your comments actually prevent mistakes( and correct crazy misunderstandings-like
mine )
your comments leave two choices to the reader,to wisen up and prevent furthur disasters, or to simply ignore or fight back with remarks like arrogant
and ignorant children(like the guy in that post) and then carry on experimenting,hoping against hope that something doesn't blow up on their
face(which eventually does happen and which puts a stop to their experiments for good)
i chose the former path and i am already becoming much smarter.maybe after another 1000 properly directed comments,i can one day hope to achieve your level of knowledge .your replies to any post(including mine) are comprehensive,
exhaustive and answer all our queries and live no doubts in the minds of the reader
chemistry always works,but not always in the way you want it to,so it is better to take good advice before its too late
[Edited on 6-10-2014 by CuReUS]
[Edited on 6-10-2014 by CuReUS]
[Edited on 6-10-2014 by CuReUS] |
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Nicodem
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| Quote: Originally posted by CuReUS | yes ,now i realize that i was a fool to come to such a silly conclusion.
it would be very helpful if you could tell more about the other factors |
I don't know enough on the topic. There are several review articles on the topic of metal dissolving reductions, perhaps you can find some relevant
information there. I posted two reviews in this thread, though they are not about nitro to amino reductions.
| Quote: | | suppose you used Fe and you displaced the FeCl3 formed with Sn or Al foil,how would you separate the Sn/Al from the mixture now.do they
form some insoluble salt that you can just filter off. |
The isolation procedure is obviously dependable on the product properties. Now, you product is amphoteric, water soluble, has a very low logP, is
oxygen sensitive, potentially metal chelating, and so on. For this reason I suggested hydrogenation as the simplest solution. I would never bother
with anything else, but if for some reason I would have to, I would opt for iron powder in methanol. I would probably use a few mol% of saturated
FeSO4(aq) to kick start the reaction (acetic acid might do as well). After the reduction is complete, you filter off the hydrated iron
oxides and any unreacted iron, wash with some methanol. You filter the filtrate trough celite or silicagel and rotavap it. Recrystallize from wherever
and avoid too much oxygen exposure.
Not sure it would work, but that is what I would try first. In case of failure, I would use iron in acetic acid and proceed the same way. It would
most likely give more iron contamination and the product might coordinate with Fe. To minimize complexation, I would use a large excess of iron (Fe to
Fe(II), but without Fe(III) formation).
| Quote: | | i have salted out acetone and IPA(which are so soluble in water) so why cant the same logic be applied here? |
I don't say it is not possible to remove Zn or Sn salts. I just said it would require a lot of development for no particular advantage. It sounds
simple when describing such a mess with words, but doing it in real life is something else. Besides, zinc chloride is too acidic to allow the product
out of the aq. phase and is also quite soluble in alcohols. At the proper pH, the mixture might be a mess with precipitated zinc hydroxide and so on.
PS: Please pay more attention to the quotation formatting. You make it difficult to read your replies.
…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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CuReUS
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so can that reaction be used to replace aqua regia ,by putting two gold electrodes in HCl or sulphuric acid and turning on the power ,the efficiency
will not be that good though
because some one wants to replace aqua regia to strip gold from computer parts in this thread
http://www.sciencemadness.org/talk/viewthread.php?tid=36959
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zed
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I would expect all of the anodized Gold (or Platinum)to eventually dissolve as a Chloride salt. The trick might be....in preventing dissolved metal
from eventually plating out on the opposite electrode. Perhaps a Semi-permeable membrane would help.
The guys in Techno-Chemistry could have better insight. Barring that, a website on the topic of Electroplating.
Might require experimentation. Just because something should work, doesn't mean it will.
In the case of dissolving Silver via HCl and electricity, I would expect that the reaction might be stopped by insoluble Silver Chloride clogging up
the surface of the electrode.
I've designed lots of interesting experiments. Most failed to achieve the results I originally envisioned.
Well, back to the side issue. A few minutes of searching yielded the following.
Pt electrolysis with HCl. It wasn't very hard to find. I gotta think it's kind of obvious, and considering the late date of the patent, possibly not
patent worthy. But....... http://www.google.com/patents/US5423957
But, we were talking about the possibility of using hydrogenation to achieve your goal. Think about it.
[Edited on 11-10-2014 by zed]
[Edited on 12-10-2014 by zed]
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CuReUS
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| Quote: Originally posted by zed | | I would expect all of the anodized Gold (or Platinum)to eventually dissolve as a Chloride salt. The trick might be....in preventing dissolved metal
from eventually plating out on the opposite electrode. Perhaps a Semi-permeable membrane would help. |
yes,i have a design in my head which i saw in bromic acid's book ideahttp://www.bromicacid.com/bookprogress.htm
under electrolysis using a bottle to make copper sulphate
also we could use one electrode as graphite so that it does not deposit on that
| Quote: | | In the case of dissolving Silver via HCl and electricity, I would expect that the reaction might be stopped by insoluble Silver Chloride clogging up
the surface of the electrode. |
but in aqua regia reaction,gold is eventually converted to chloroauric acid so i think it will be soluble.also have you tried wrapping the electrodes
with steel wool(or glass wool,i cant remember) ,that might prevent it from clogging
| Quote: | | I've designed lots of interesting experiments. Most failed to achieve the results I originally envisioned. |
wouldnt be bad if you could share some of your ideas and the outcomes
| Quote: | | But, we were talking about the possibility of using hydrogenation to achieve your goal. Think about it. |
yes ,i agree that nicodem was right ,but as i said in my previous post to nicodem,i cant do that because i dont understand the procedure
yet(hydrogenation over a balloon?)
now i am thinking about using some sulphide salt as a possible reducing agent as the metal/acid reduction takes a lot of time,and you also need a lot
of the metal(3:1 ratio of metal -nitro compound)
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Nicodem
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| Quote: Originally posted by CuReUS | | yes ,i agree that nicodem was right ,but as i said in my previous post to nicodem,i cant do that because i dont understand the procedure
yet(hydrogenation over a balloon?) |
"Hydrogenation over a balloon" is just a phrase for a normal hydrogenation at atmospheric pressure. It only takes a flask, a magnetic stirrer, a
septum, a needle and a balloon. Nothing special, except perhaps an inert gas to purge out the air, but even that can be improvised in an amateur
setting. I did this kind of a hydrogenation in my bathroom when I was much younger (This does not mean that I (still) approve of using the bathroom
for chemical experiments! I got wiser now.).
If you are afraid of hydrogen, you can use CTH with cyclohexene instead (such a preparation of 2,4-diaminophenol is described in DOI:
10.1039/JR9540003586).
An alternative amateurish method is the reduction at the cathode. We have a thread on this topic. Apparently the 2,4-diaminophenol dihydrochloride is poorly soluble in concentrated hydrochloric acid so that would make
for a good electrolyte. You would maybe have to use some methanol as a cosolvent which may affect the dihydrochloride solubility, but should be easily
removable by concentration. In fact, the only reliable procedure for the metal dissolving reduction of 2,4-dinitrophenol to 2,4-diaminophenol employs
this trick with the dihydrochloride to isolate the product from the reaction mixture (using Sn and conc. HCl; DOI: 10.1039/P19870000851). This
procedure is simple and gives a good yield of the product as the dihydrochloride. Liberating the aniline could perhaps be done with
Na2CO3 in methanol under nitrogen, followed by filtration and solvent removal.
By the way, electrochemical reduction of m-dinitrobenzene in acidic media also gives 2,4-diaminophenol (Current Science, 12,
151-153). An alternative using Al is described in US2525515, but no yields are given (we have two threads on the topic of such aminophenols from
nitrobenzenes syntheses that you might want to check).
[Edited on 12/10/2014 by Nicodem]
…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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zed
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Like that.
http://www.orgsyn.org/demo.aspx?prep=cv9p0589
If the pressure gauge were replaced by a balloon, you would have a very simply built hydrogenator. The rest of the article doesn't much apply to what
you are doing, but at least you have a picture.
[Edited on 12-10-2014 by zed]
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CuReUS
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nicodem
yes ,i also used to experiment in the bathroom, that to in the dead of night until a little accident wisened me up
although i must say that i feel a bathroom is one of the safest places to work as the walls and floors are tiled making it fire proof and also easy
to clean in case of a mess
with one or two halon fire extinguishers with thermal fuses,what more could you ask for also there is a shower station in case the chemical god is not pleased with you
i didnt give much importance to the electrochemical reductions due to the long reaction times ,also in some e- reductions ,i think you have to use a
clay pot with a semi permeable diaphragm and also are electrochemical reductions efficient,but now i will look into it
that you are telling me that 2,4-DAMP is insoluble in HCl comes as a bit of a surprise because when i did my Zn/HCl reduction and filtered the
solution i got a clear to slightly pinkish solution although the original solution had not become colorless (as i had imagined) but a tan yellow,
almost tea color ,meaning that some of the nitro compound was still not reduced.
i did not put any colsolvent like ethanol or IPA because i was scared that a side reaction would take place so i dont know if the solubility of the
nitro compound would have improved or not
but the last reaction you talk about is actually beautiful
i have read about the bamberger rearrangement of n-phenyl hydroxylamine to para-amino phenol in presence of sulphuric acid and catalyst but meta
dinitrobenzene to DAMP ,just amazing
ZED
thanks for the link,but it is not opening now ,i will try again later
also in our electrochemical discussion ,i had another idea for preventing silver choride depostion if the wool idea didnt work
why cant we try to covert the silver chloride into a complex compound that can be later broken down to give the silver with the help of strong
acids
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zed
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One problem at a time. Silver was just an aside remark. Like anodizing Aluminum.
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zed
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Oh, in response to your complex Silver compound idea......DON'T! Unless you really know what you are doing, complex salts of Silver can be quite
dangerous to work with. They like to explode. Famous for it, in-fact. Moreover, you may be unaware that you have formed a complex-salt. This can
be simple as mixing Silver Nitrate and Ammonia.
http://en.wikipedia.org/wiki/Tollens%27_reagent
These explosive tendencies may be shared by the complex salts of other metals, Nobel metals especially. Always good to check.
[Edited on 16-10-2014 by zed]
[Edited on 16-10-2014 by zed]
[Edited on 16-10-2014 by zed]
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