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Author: Subject: Nitroethane - Does the ntirite have to dissolve?
unome
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[*] posted on 21-10-2009 at 15:33
Nitroethane - Does the ntirite have to dissolve?


I am wondering on this question - seems to me that there are numerous ref's starting to pop up where the nitrite is merely sitting there as a finely divided solid, or attached to a basic resin, and the ethyl halide is then passed through (either as a liquid or gas)...

Anyone got any ideas?

Seems to me that if the labeled [C11]Nitroalkanes can be made by passing Ethyl Iodide through heated silver nitrite in a column and the report (attached) where the basic resin Nitrite can be used to form it from liquid Ethyl Iodide, then we could fuck off the DMF/DMSO altogether and just put Sodium nitrite/Silica in a jar with ethyl halide (l) and wait?

Attachment: Kornblum.NitroparraffinSynthesis.pdf (656kB)
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Attachment: Synthesis.Nitroalkanes.Polymer.Supported.Nitrites.pdf (56kB)
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[EDIT]

This is from page 127/167 of a VERY interesting thesis I found online - a whole bunch of safrole derivatives - MDP2P (via Wacker), Nitropropanes (including the Nitrosafrole), etc. with Shulgin as the external examiner... Notwithstanding all of that, here is the preparation of Nitroethane:

Quote:
Nitroethane

Ethyl iodide (3.12g, .02 mole) freshly distilled was stirred in an ice bath at 0'C. Small portions of dry AgNO2 (3.08g., .02 mole) prepared as described (579) were dropped in. The internal temperature rose to 16'C. The reaction mixture was left overnight (12 hr.) in a cold water bath at 15'C and distilled at atmospheric pressure (739 mm). First fraction (70-75'C) (ethyl iodide 1.84g) and second fraction (108-115'C), (nitroethane, 570mg) were collected.

Yield: 38% (95% conversion).


I cannot attach the relevant paper - so I'll get someone else to throw it up on 4shared here: http://www.4shared.com/file/142572325/d8b506fc/ThesisLabeled...

(As a point of interest - I have not seen a single Wacker oxidation of isosafrole using PdCl2/CuCl2 as early as 1975 - could this be the first one? [NB @ pp-128-9 of the PDF])

BTW - I'm unsure of the solubility of AgNO2 in EtI, but it seems manifestly unlikely that it is soluble, mol:mol so it would seem to bear out my hypothesis?

[Edited on 22-10-2009 by unome]

[Edited on 22-10-2009 by unome]
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[*] posted on 21-10-2009 at 16:15


I'm a bit lost on the entire process, but logic tells me that if the nitrate is solid on the bottom, then it's not bonded to the ethane at all.



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[*] posted on 21-10-2009 at 19:08


One assumes the '95% conversion' relates to recovered ethyl iodide. I doubt whether the researches recovered the AgI2/AgNO2, separated them and established conversion.

AgNO2 has reputed solubility in EtOEt, diethyl ether but its difficult to imagine it being appreciably soluble in an alkyl halide. That said it must have 'some' solubility in ethyl iodide otherwise one would not see the reaction proceed to this extent over such a short period, especially given the mechanism would involve an Sn1 mechanism, rate determined by reactant concentrations, steric effects of ethyl iodide (not to bad i guess primary halide, short chain, iodide a little bulky), leaving group ability (someone should try this on the tosylate) and solvent effects (this reaction apparently can be performed with NaNO2 if a non-polar aprotic dry solvent like DMF is used).
Anyway in response to your question, no the nitrite does not have to completely dissolve........but the formed AgI2 will deposit over the undissolved AgNO2 stopping it from re-dissolving as it is consumed. Time and pressure should push things towards a better yield.




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[*] posted on 21-10-2009 at 19:55


What about if the nitrite were deposited on a large surface area carrier, like silica for instance? Precipitation or even just allowing a solution of a nitrite to dry on a large excess of silica would presumably avoid a lot of the issues from excess iodide formation blocking the nitrite? Maybe use anhydrous ethanol as a solvent for the ethyl halide? It really shouldn't get in the way and the nitrites aren't likely to be soluble in it either
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[*] posted on 26-10-2009 at 16:37


Quote: Originally posted by unome  
What about if the nitrite were deposited on a large surface area carrier, like silica for instance? Precipitation or even just allowing a solution of a nitrite to dry on a large excess of silica would presumably avoid a lot of the issues from excess iodide formation blocking the nitrite? Maybe use anhydrous ethanol as a solvent for the ethyl halide? It really shouldn't get in the way and the nitrites aren't likely to be soluble in it either


But don't you want the nitrite to add? Its not a catalyst, its the bit you want substituting with the iodide. These short chain nitro parrafins are quite interesting, if it wasn't for the fact that nitro ethane is public enemy no.1 (or maybe no.18) the fact that they are impossible to elegantly creat via substitution would go unnoticed. Unfortunately my interest is academic, the experimentation is up to you (although please share the results).
If i had to choose a set of substitution reagants/conditions i would piss the iodide off, make the ethyl tosylate (kind of arduous however its a confirmed synthesis) and try to react it with the sodium nitrite in a non polar aprotic, like dry dry dmf or dmp.
If that doesn't work messing around with poorer leaving groups and solvents seems pointless.

Actually reading my post now i understand the great benefit of supporting the nitrite. If you choose the support carefully you can greatly favour nitro over nitrite substitution by having a support that binds to the oxygen rather than the nitrogen on the nitrite.
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[*] posted on 26-10-2009 at 17:23


I'm waiting on two papers from Kornblum, the one where he uses Sodium Nitrite with DMSO and the one where he discusses at length the reasons why Silver/Na Nitrates undergo different reactions, giving different products (although I take some heart from the fact that he points out that Silver, while good, is not unique in this regard)...

Getting a route - preferably sans solvent - to these nitroparaffins from simple alkyl halides would be a useful improvement for the home chemist, there are numerous reactions were they would be useful, not simply the verboten ones (although I will tell no lie, those are the ones that interest me most:P)

Here is one I just noticed:

Quote:
[11C]Ethanenitronate was synthesized by the displacement of iodide from [l1C]ethyl iodide by nitrite. In a typical reaction 100pCi of [11C]ethyl iodide (Amersham Corp., 57 mCi/mmol) was equilibrated with 250 pmol of unlabeled ethyl iodide for 2 h at room temperature and for 16 h at -10 'C. Subsequently, the reaction was initiated by addition of 1 ml of dimethyl sulfoxide containing 2 mmol of NaNO2. The reaction was terminated after 1 h by addition of 25 ml of 1 mM KOH. Prior to adsorption of the product onto a column of AG 1-X8 (hydroxide form) the pH of the solution was adjusted to 11.5 with 1 M KOH. Nitrite and nitrite esters were eluted from the column with 50 ml of 5% dimethyl sulfoxide. The column was rinsed with 50 ml of deionized H20, after which the product was eluted with 0.1 M KOH. Fractions which contained ethanenitronate (as estimated by A240 measurements) were pooled, and the pH was adjusted to 5.5 with solid monobasic potassium phosphate. Nitroethane was extracted from this solution (20 ml) with two 1.5-ml aliquots of methylene chloride. The methylene chloride extracts were pooled, and the ethanenitronate was extracted into 1 ml of 0.2 M KOH. Finally, the pH of the ethanenitronate solution was adjusted to 11 with 1 M HCl. The final product was an 87 mM solution of ethanenitronate (35% yield)

Taken from the attached paper (Porter & Bright, Ethanenitronate Is a Peroxide-dependent Suicide Substrate
for Catalase*, Journal of Biological Chemistry (1987) 262(20), 9608-9614), page 2/7 (first column, about 1/4 to about halfway down the page)


Not too shabby - small amount of NaNO2/DMSO solution added to a much larger amount of ethyl halide, no fucking silver salts... Presumably distillation of the nitroethane (and the unreacted ethyl iodide would be significantly simpler than the column)

Attachment: Ethanenitronate.Substrate.Suicide.Catalase.pdf (845kB)
This file has been downloaded 435 times

I'll throw the Chem Abstract in as well (one by a chap called Meyer funnily enough:D)



[Edited on 27-10-2009 by unome]

Attachment: Meyer.Nitroethane.pdf (152kB)
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[*] posted on 27-10-2009 at 18:14
Kornblum papers


JACS 78 1497-1501 (1955)

Attachment: nitroethane.kornblum.dmf.pdf (661kB)
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[*] posted on 27-10-2009 at 18:21
Kornblum Papers


JOC 22 455-6 (1957)

Attachment: nitroethane.kornblum.dmso.pdf (274kB)
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[*] posted on 28-10-2009 at 12:40


What would be interesting is whether or not another metallic salt could be swapped for silver nitrite, Kornblum definately stated that Silver, whilst good, is not unique... With a little luck, perhaps even some thought, a replacement therefore might be able to be found?:)

This would require a "REAL" chemist - the paper cited above by Kornblum where he states the same, is the one in which he attributes the problem to the Sn1/Sn2 nature of the reactions - I do not pretend to understand it, either why it works with NaNO2 in DMSO, or why it doesn't without solvent, whilst it does with AgNO2... All I can do is work by analogy, whether or not it is possible to substitute another anion for Silver in the Kolbe nitrile synthesis would be an obvious starting point (given the AgCN is mentioned by Kornblum in that paper).

Following that train of thought led me to the Hard/Soft-Acid/Base theory (HSAB)... So what would be a suitable soft acid to replace Ag & thus react with the soft-base I? Presumptively Hg/Pt/Au/etc. are out, any ideas?

NB Kornblum's Rule (as it is stated).. is that where a hard lewis acid (? sodium?) is used, the soft Alkyl bonds to O, whereas when the soft acid (Ag) is used, the alkyl bonds to N...

Given the insolubility of Silver halides, perhaps the equilibrium would also come into play as well....

What about borderline acids? Pb/Ferrous? Cu is out (forms coordination compounds)... Pb would be useful - the chloride would react similarly to the Silver salts, which would be of use if the equilibrium needed a push...

[Edited on 28-10-2009 by unome]
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[*] posted on 4-11-2009 at 20:37


Here is two on the use of a column to form the nitroalkane(s) from sodium/silver nitrite in a column... Silver works better, but there is at least some suggestion that around a 20% yield can be had by running methyl iodide through the sodium nitrite/silica column @100C.... Hopefully that translates to ethyl halides...

An obvious choice would be to utilise this with a major excess of the alkyl halide so that the majority of the sodium nitrite can dissolve, then simply separate the excess alkyl halide from the nitroalkane product (40-odd degrees C difference in BP so that shouldn't be too difficult).

Attachment: Synthesis.11C.PEA.Amphetamine.from.11C.Nitroalkanes.pdf (391kB)
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