Vaaguh (Hive Bee)
03-23-04 17:18
No 496848
       3,4,5-trimethoxynitrosyrene rdxn trouble     

Hi,

After performing the NaBH4/IPA/H2O reduction of recrystalized 3,4,5-trimethoxynitrostyrene the nice white solution always turns to a deep yellow color after adding dilute acetic acid to quench the excees borohydride, deduced from bariums trials the 3,4,5-trimethoxynitroethane is supposed to be a white solid. A yellowish oil however is always recovered. As for the details a 1,3 molar excess of NaBH4 was used and from the fizzing it definately shows that there is some excess borohydride in the post reaction mixture.

Does anybody know what could be the cause of this spontaneous color transformation?
Hippler 		 
 
 
 
    Barium
(Heavyweight Chempion(eer))
03-23-04 21:26
No 496876
       Have you given the oil time to crystallise?     

Have you given the oil time to crystallise? Right now I can't remember if I have gotten the nitroalkane as an oil which later solidified. But it would not seem too strange since there is a lot of alcohol present which can prevent immediate crystallisation. Isolate the oil and store it overnight at room temp and see what happens. I know that 1-(2,4,5-trimethoxyphenyl)-2-nitropropane falls out as an oil first if there is too much alcoholic solvent present. It has taken up to five-six hours for it to solidify completely on occasions. 		 
 
 
 
    Vaaguh
(Hive Bee)
03-23-04 22:40
No 496888
       will try!     

Thanks for the information, the alcohol was stripped but the oil was not given time to solidify. Yesterday a new reduction was started but there was no time to work it up, i will post the details in a few days.
Hippler 		 
 
 
 
    Barium
(Heavyweight Chempion(eer))
03-24-04 00:57
No 496921
       Ouch! I would not leave such a reaction ...     

Ouch! I would not leave such a reaction mixture for a couple of days and expect a good yield of nitroalkane. 		 
 
 
 
    Vaaguh
(Hive Bee)
03-24-04 00:58
No 496922
       as a side note     

After a quick peek there seems to be a lot of white solids in the now yellow NaBH4 post reaction mixture (could be all borate salts ofcourse but that is doubtfull). The mixture shouldnt have left sitting there like that blush



The starting 3,4,5-trimethoxynitrostyrene that was used had been recrystalized twice and gave a sharp mp of 118-119 °C.
One hour after the addition of the nitrostyrene the alcohol/water solution was milky white.

The yellow oil obtained from previous NaBH4 reductions of 3,4,5-trimethoxynitrostyrene (10 mmol runs) gave upon reduction of the nitro group using zinc/formic acid or zinc/potassium formate a wide variety of yields ranging from excellent to none.

Would anyone know what a good TLC solvent system would bee for 3,4,5-trimethoxynitrostyrene/3,4,5-trimethoxyphenylnitroethane?
Hippler 		 
 
 
 
    Sunlight
(Pioneer Researcher)
03-26-04 18:20
No 497532
       CH2Cl2     

There's a scientific paper in wich they reduce nitrostyrenes with IPA:CH3Cl3 and silica gel with NaBH4. In his example, may be 3,4 DMNS or similar, they use CH2Cl2 as TLC solvent, the nitroethane was at about 0.8 and the dimeric imputity at about 0.6. Unfortunately I don't have the paper at hand. I made it and I believe to remember that for 2,5 DMNS the nitrostyrene and nitroethene were in the same place (test it) and the impurities were lower. I hope it can help. 		 
 
 
 
    Rhodium
(Chief Bee)
03-26-04 19:31
No 497544
       silica-gel assisted reduction     

Sunlight: The article you are thinking of has been posted here: Post 492478 (Rhodium: "Not novel, but a classic reference", Novel Discourse)
The Hive - Clandestine Chemists Without Borders 		 
 
 
 
    Panoramix
(Stranger)
03-27-04 03:45
No 497612
       The best     

You are the best, rhodium.