Sciencemadness Discussion Board - is 2,5-dimethoxyphenyl-2-nitroethane a white solid at r.t.?


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Sciencemadness Discussion Board » Fundamentals » Organic Chemistry » is 2,5-dimethoxyphenyl-2-nitroethane a white solid at r.t.?

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stoichiometric_steve

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posted on 29-10-2007 at 08:56

is 2,5-dimethoxyphenyl-2-nitroethane a white solid at r.t.?

after the reduction of 2,5-dimethoxy-ß-nitrostyrene using NaBH4 and subsequent workup (removing water soluble salts), i ended up with a yellow oil mixed with a lot of a white, probably crystalline substance.

since i have not found any physical data for 2,5-dimethoxyphenyl-2-nitroethane, i am not sure whether this is the desired product or not.

upon digesting the mixture with MeOH and keeping it in the fridge for a few days, more solids aggregated.

all NaBH4 double bond reduction writeups for this substrate state that the reaction yields a yellow oil, so i'm not sure whether the solid mass obtained is the dimer or some other undesired product.

ssdd

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posted on 29-10-2007 at 09:15

I am not sure what type of equipment you have on hand or if you are doing this at home, but they way I would deturmine this is as follows.

Take a small sum of the crystalline powder and run it through a GC/MS. This should give the atomic weight of the crystal, if you know the atomic weight of your product you can make a guess as to if its impurities or the product. This has worked for several intermediates in a research project I am working on when I had an unknown large crystal fall from solution.

hope this helps,
-ssdd

All that glitters may not be gold, but at least it contains free electrons.
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Klute

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posted on 29-10-2007 at 09:49

Try melting the crystals, they could inorganic salts from the borohydride reduction, I remember this beeing mentionned at the hive a couple of times. IIRC, Barium reported this nitroalkane as been obtained as a yellow oil, but that could crystallize at room temp when sufficiently purified. If it melts at a low mp, it's urely the nitroalkane, otherwise it could be boron salts.

stoichiometric_steve

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posted on 29-10-2007 at 10:02

yeah ssdd, if only i had a GC/MS...

TLC will have to do. i'll try to take a m.p. asap.

jam640

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posted on 29-10-2007 at 10:09

Yes, most likely boron salts. They have a tendency to precipitate after a while unless extensive care is taken during the workup after reduction. Sucks.

Klute

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posted on 29-10-2007 at 13:37

Can't you distill that one too? Or did you simply want to check the crystals were some nitroalkane?

stoichiometric_steve

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posted on 29-10-2007 at 22:11

as already stated, it is quite unlikely that the solids are boron salts, since the organic phases were carefully washed after the reduction. i think the solids are soluble in acetone...

Klute

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posted on 30-10-2007 at 06:50

Coming to think of it, I also had some very fine whitish solids with a nitroalkane... When recrystallizing from MeOH, threy caused turbidity, but were impossible to filter through regular filter paper, glass frite, or porous membranes. I just left them there. The nitroalkane had been washed too. I considered them as some dimeric impurities. But it was a small amount.

How many BH4- eq. were used? 4x or less? Did you try weighing the obtain solids? Maybe all the oil crystallized... If it is the nitroalkane, then it must be quite pur, and gives a possibility of purifying further, without distillation. Congrats!