Antoncho (Stranger)
09-07-00 17:51
No 49720
      One more idea for LAHless nitrostyrene reductions  Bookmark   

Does anyone know what happens if you reduce a nitrostyrene with a non-complex hydride, like, say, NaH? Maybe it can serve as a LAH substitute? Maybe, like in NaBH4 reductions, nitrostyrene/propene can be turned into nitropropane/ethane, and to the final amine via Clemmensen?
I mean, the major advantage of NaH is that it can be self-made, and in the place where I live metallic sodium costs about 150 times less than LAH.
Any information will be greatly appreciated since I just can't afford the damn stuff and I'm not alone at that I guess.

 
 
 
 
    Rhodium
(Sexy, Sexy, Sexy)
09-08-00 12:47
No 49995
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

NaH is not a good reducing agent, it is mostly just a strong base.


http://rhodium.lycaeum.org
 
 
 
 
    CHEM_GUY
(Hive Bee)
09-08-00 19:32
No 50067
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

You could try a real ghetto metal hydride:  Places sell Nickel Metal Hydride batteries, NiMH.  Add that to a solution of nitro-styrene...

Try electrochemical, or hydrogenation of metals.


Read my Disclaimer:  http://cantsueme.homestead.com
 
 
 
 
    halfapint
(Hive Bee)
09-10-00 22:28
No 50632
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

In an organic chem text a few years back, I read that sodium, aluminum and hydrogen would combine into sodium aluminum hydride "by direct union of the elements". This was a very casual, unreferenced sentence mentioning contemporary work. I would expect this synthesis to occur at elevated temperature, though that was not stated. For sure, NaAlH4 can bee directly substituted for LiAlH4 in any and every reduction, by adjustment of the quantity. If getting sodium is easy, you are the bee to give us the report on sodium aluminum hydride!


surroundsoundreverbfuzzbustersleagueresonancemodulation
 
 
 
 
    hest
(Newbee / Eraser)
09-11-00 00:58
No 50681
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

Sodium and hydrogen at app. 300C gives NaH
NaH and AlCl3 (and a bit NaAlH4) gives NaAlH4
The first is hard to doo at home, the next i dificult.
NaH and AlCl3 is easye to get and a way to make the NaAlH4
LiH is also easye to get, someone use it as a solid source og H2 (24l in 7g)
But for small scale production, i do not think it is worth the troble.
And large scale prod. is easyer with H2 and presure
 
 
 
 
    halfapint
(Hive Bee)
09-11-00 20:42
No 51004
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

Alas for the days of grammar and rhetoric!
Don't the schools teach Greek and Latin any more, deportment and oratory?

It's OK, hest, just wanting to poke fun at your spelling while I'm thanking you for the data.
"the next i dificult" just doesn't communicate to me; do you feel that reacting NaH with AlCl3 is or isn't difficult to do?
I might either agree or disagree with your opinion, if I knew what it was.
Did you imply that 24 liters of gaseous hydrogen can be produced by 7 grams of lithium hydride?
Let me encourage you to use more keystrokes.

Hey, I talk like this when I'm with my hog biker buddies. They dig.



surroundsoundreverbfuzzbustersleagueresonancemodulation
 
 
 
 
    hest
(Newbee / Eraser)
09-11-00 22:43
No 51025
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

It's ok to make fun of us foreign people, we have a lot of humor. If you think my english is bad you should see my german and french.(but i'm caple of communicate on these language too)
Yes the mixing of NaH and AlCl3 is hard to doo, the reaction is dificult to start and takes some time. You end op with a thick solution and ewerye thing has to bee dry. I once thort( ups i mean thought) that LiH and AlH3(ups i mean AlCl3) was the way to cheap LiAlH4, but i ended up with bying it from Aldrich. And yes two mole of LiH gives one mole of H2 (Yea i know, 14g (not 7) LiH gives 24l H2)


 
 
 
 
    KrZ
(Hive Bee)
09-12-00 00:00
No 51049
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

Nitrostyrenes are a big hassle. We NEED more cyanohydrin routes to PEAs, I demand references!  I've been looking myself but have yet to turn anything up :-(
 
 
 
 
    Rhodium
(Chief Bee)
09-12-00 00:24
No 51058
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

There is a US patent which reduces benzaldehyde cyanohydrins to phenethylamines with phosphorous pentasulfide, but I don't have its number handy. Perhaps it can be found using a patent search engine?


http://rhodium.lycaeum.org
 
 
 
 
    KrZ
(Hive Bee)
09-12-00 09:33
No 51245
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

Thanks for the tip rhod. I will continue digging until something turns up.
 
 
 
 
    halfapint
(Hive Bee)
09-12-00 15:06
No 51311
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

Excuse me, Hest. I was not aware English was not your first language. (Had you studied Greek, Latin, deportment and oratory for real, it would have helped in spelling several languages!)

You once thought (not thort) that LiH and AlCl3 was the way to cheap LiAlH4, I take it, not AlH3.

What solvent were you using to combine NaH and AlCl3, that got so thick? What temperature? Would a seed amount of NaAlH4 have made it start quicker?

Uh, cyano what?


surroundsoundreverbfuzzbustersleagueresonancemodulation
 
 
 
 
    hest
(Newbee / Eraser)
09-12-00 19:37
No 51392
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

All forgiven halfapint, if I get the time I will take a class in latin ;-)
I used Ether and diglyme as solvent.
I did not heat it, but sometimes it did it by its self :-(
Yes adding some LiAlH4 would help (See H.I.Schlesinger Am.Soc.,69,1199,(1947))

 
 
 
 
    halfapint
(Hive Bee)
09-13-00 11:12
No 51662
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

don't post sources


surroundsoundreverbfuzzbustersleagueresonancemodulation
 
 
 
 
    Ritter
(Stranger)
09-13-00 19:46
No 51745
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

KrZ:
Here are two old refs on reducing mandelonitrile derivatives:

Benzoyl derivative:  J. Am. Chem. Soc., 50 3373 (1928)
O-carbethoxymandelonitrile derivative: Ann., 564 49 (1949)

KrZ, could you please post the ref you mentioned concerning the acetyl derivative of mandelonitrile?

Tks
Ritter
 
 
 
 
    perpeetuum
(Stranger)
05-24-01 00:05
No 196540
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

So here is 'quite possible' way to produce own (and relatively cheap) LiAlH4 from LiH and AlCl3 in (anhyd.)Ether as a solvent under good stirring ang temperature something above the room one (40-50 C degrees). Atmosphere could be the 'normal' air, but the reaction should take plenty of time, if it is really possible...tongue
....I would accelarete it in MW (on very mild irradiation) a little--- this could help. But not above 70 C deg.
 
 
 
 
    Greensnake
(Stranger)
05-24-01 12:23
No 196647
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

Hmmm, ain't Red-Al preparation from scratch kinda simpler than LAH, for all the same purposes?
 
 
 
 
    perpeetuum
(Stranger)
05-24-01 20:38
No 196716
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

maybe little simpler - and good for learning - and also via rP/HI you obtain also boranes, iodides and phosphines ---> that means hangovers cool

but be quiet. the masters of chem-science are speaking. we are only aprentices, so rather listen and learn, so as me :)
 
 
 
 
    smiley_boy
(Hive Bee)
05-25-01 02:38
No 196781
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

Antocho, zdravstvooytye, droog! G'de della?

So, you want to reduce nitrostyrenes, but you don't want to use LAH? I'm assuming you must not to want to use hydrogenation either, though when it comes to economies of scale, this method effectively reigns supreme.

I like your thinking. Yes, NaAlH4 will do the trick as others have pointed out, but then you have the problem of acquiring or producing that.

Alternatively, under aprotic conditions you can combine NaBH4 and add a little LiCl (or better yet LiBr) to obtain LiBH4 in situ - a much, much more powerful reducing agent.

Here's a quick, overly-simplified lesson on the chemistry of borohydrides and aluminum hydrides and their activity. When the metals complex with BH4- or AlH4-, the relative size of the metal atoms has a huge effect. For example, with Li+, the overlap of electron orbitals around the Li is much too small to really overlap much with BH4-, plus lithium is not so free-and-easy with giving up its elecxtrons like a cation is supposed to (at least compared to other metals.) The result: the borohydride is very reactive. LiBH4- readily reacts with water or simple alcohols, just like LiAlH4. LiBH4 can reduce nitro groups to amino groups.

If instead we complex BH4- with Na+, we have a much better match-up. Na+ has a much larger electron cloud, and is much more willing to give up its electrons. Hence, we have a much more stable complex, and NaBH4 is fairly stable  even in the presence of water or alcohols. It isn't going to be able to reduce a nitro group.

If we go further down the table of elements, we will have KBH4, a compound that is even more stable.

Incidentally, there's also the classic rocket fuel Aluminum borohydride ( Al(BH4)3 ) as well - made by reacting 1 AlCl3 with 3 NaBH4 under aprotic conditins, this is actually a distillable liquid, and is extremely pyrophoric. Now with three borohydrides all sharing one stingey, pitiful little metallic center, this one really has some reactivity. As far as nitrostyrene reduction goes, I'm sure it'll get the job done; just don't expose it to moist air, or BOOM!!

Now, back to your question: what other options are out there? Well, there's electrolytic reduction, there's Vitride in toluene, there's zinc amalgam in alcohol, and borane in THF or ether. Actually, for the price, there's also sodium amalgam - once the method of choice, now poo-pooed for a number of different reasons.

I hope this helps...
 
 
 
 
    smiley_boy
(Hive Bee)
05-25-01 03:02
No 196785
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

Actually, speaking of borane, that seems like a topic that hasn't been as well addressed as I feel it should. Now, correct me if I'm wrong, but borane*THF can be produced from sodium borohydride by partial decomposition with sufuric acid in THF:

2 NaBH4 + H2SO4 + 2 THF -> 2 BH3*THF + Na2SO4 + 2 H2

So why isn't this taken advantage of? The reduction of nitrostyrenes using borane-ether complexes is a well-established procedure in the literature, providing good yields  and remarkable chemoselectivity; for some arylethylamines, its the only practical route. So why aren't people experimenting with this around here? Am I forgetting something?

To make myself more clear, this is what I'm proposing: you can replace the LiAlH4 in your average nitrostyrene reduction procedure with NaBH4 and H2SO4! Safe, cheap, available. How's that for practical? Hopefully this generates some interest...
 
 
 
 
    Osmium
(Stoni's sexual toy)
05-25-01 12:02
No 196937
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

As far as I know NaBH4 is pretty expensive in the former Soviet Union. Or so I've been told. Could it be that this substance wasn't produced industrially, while Li was? Would make sense, since Li is/was processed for nuclear weapons purposes, one of the isotopes is used for hydrogen bombs (lithium deuteride). I remember that a few years back many of the available Li compounds had a slightly different molar weight compared to the naturally occuring isotope mixture, becausepart of the isotope in question had been removed prior to conversion to other compounds.
 
 
 
 
    Rhodium
(Chief Bee)
05-25-01 13:59
No 196961
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

The H2SO4 can be replaced with I2 or methyl sulfate (or was it methanesulfonic acid?). There has been quite a few refs on this posted here at the hive (the original refs used the reducing agent to reduce amino acids to amino alcohols, but it would be suitable for nitrostyrenes too, as BH3*THF is a known nitrostyrene reducing agent).


http://rhodium.lycaeum.org
 
 
 
 
    sunlight
(Hive Bee)
05-25-01 14:25
No 196978
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

Could anyone post a possible procedure for nitrostyrene reduction with THF, NaBH4 and H2SO4 ?
I can run it almost immediatly.
And phosphorus pentasulfide is not expensive, it could be other good option.
 
 
 
 
    foxy2
(Hive Addict)
05-25-01 14:42
No 196986
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

Nobody mentioned Zn-Hg?
That seems like a reasonably yeilding procedure.


Do Your Part To Win The War
 
 
 
 
    Rhodium
(Chief Bee)
05-25-01 16:27
No 197007
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

The byproducts from a phosphorous pentasulfide reduction consists of what? SO2 and H3PO4?

Foxy: Zn/Hg is supposed to be a moderately good reduction method (yields 50-75%) but it uses A LOT of mercury (about 10% of the weight of Zn). Not good for Gaia.


http://rhodium.lycaeum.org
 
 
 
 
    Osmium
(Stoni's sexual toy)
05-25-01 17:38
No 197021
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

Preparing Zn/Hg qaccording to most old refs is a messy reaction, usually requiring stirring of Zn with excess Hg salt solution for an hour or so. But there are better ways to prepare Zn/Hg.
I used this method:
Zn powder was covered with plenty of water, and some conc. HCl was added. Vigorous reaction of the Zn with the HCl. This removes the oxide coating on the Zn. Stir mixture well and add a spatula of Hg salt. H2 evolution stops almost immediately, due to the overvoltage phenomenon of Hg. Drain water, wash Zn/Hg with more water or EtOH or solvent of choice, and use in your reaction.
 
 
 
 
    foxy2
(Hive Addict)
05-25-01 18:09
No 197025
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

Is the huge amount of Hg necessary?

I have always wondered why the Al/Hg uses very small amounts while the Zn/Hg uses huge amounts of Hg

Osmium, did you get decent yields using modest amounts of Hg salts?  Or are the large amounts truely necessary?
lates
Foxy


Do Your Part To Win The War
 
 
 
 
    smiley_boy
(Hive Bee)
05-25-01 19:32
No 197044
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

Foxy2,

Hey there. Actually, I did mention Zn(Hg), but I have to agree with Rh about its downsides.

If memory serves, unamalgamated Zn reduces nitrostyrenes to hydroxylamines. I can't remember where I read this, but I'm sure there are references for it somewhere.

Antocho,

Stupid 12 hr rule! Obviously, that should say say "Kak dela?" Oops.
 
 
 
 
    sunlight
(Hive Bee)
05-25-01 20:32
No 197054
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

There's also the russian patent (water, HCl, Zn), and it seems nobody have tested it. Anyway even if it works is only for small scale reactions, we need to find something more workable.
I insist in trying the THF.BH3 way. In TSII there's a sample for phenethylamine, but I don't see clearly the way to make the THF.BH3 from NaBH4 and H2SO4, just adding with stiring the equimolar amount of acid over the NaBH4-THF ?
 
 
 
 
    foxy2
(Hive Addict)
05-25-01 21:02
No 197061
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

Well I have no problem with hydroxylamines, considering they are usually just as active as the amines
MDOH-shulgin commentary

Anyone have success with unamalgamated Zn?
Anyone have a ref for this, i like the sound of unamalgamated
cool


Do Your Part To Win The War
 
 
 
 
    halfapint
(Hive Bee)
05-29-01 06:56
No 197200
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

Smiley_Boy, I gotta hand it to you, you kicked down more than your share of outstanding methods here. This is a dynamite thread on reducing agents. Would the borane complex form in dioxane, as well as THF? (Dioxane, n. the distillate of ethylene glycol with dilute sulfuric acid. All solvent ethers, including cyclic ethers, should be distilled with a reducing agent like a ferrous salt to eliminate peroxide explosions.) Yet THF is obtainable from OTC formulations.

Neat trick with the lithium borohydride. Perhaps that's why nearly all elementary lithium salts are watched some places. I once considered trying to get it out of grease, hee-hee, before they started making those handy batteries. I learned from that pointer about the atomic radii.

Direct combination of sodium, aluminum and hydrogen still sounds cleaner to me than messing with aluminum chloride intermediate. Plus it's a process design challenge, depending on what temperature is required. Someday I'll build my hydrogen tower, a vertical countercurrent furnace with solids or liquids dropping from the top through a blast of hot hydrogen. Better warn the neighbors.
Edit:

for the price, there's also sodium amalgam - once the method of choice, now poo-pooed for a number of different reasons.


The deprecated sodium amalgam is available without recourse to elemental sodium, just by electrolyzing NaOH solution with a mercury cathode. When the mercury solidifies, it has absorbed enough sodium for use. This is also a prep for metallic sodium, by distilling off the mercury, a Really Hazardous Operation.



The whip hand, in reach, can take control from the gun hand.
I've done that.
Some say I'm bad.
 
 
 
 
    halfapint
(Ubiquitous Precursor Medal Winner)
09-01-01 19:03
No 209305
      Re: One more idea for LAHless nitrostyrene reductions  Bookmark   

As Lugh mentioned to me, I should have said electrolysing NaCl solution. I know I would have caught this error before I started dropping my mercury metal into lye. I have also seen a post in another thread, which says distillation of mercury is much safer if it is collected in water. Sounds reasonable to me; it also ensures that no sodium vapor which might have made it over will bee present in your mercury.

turning science fact into <<science fiction>>