| Quote: | 50 ml IPA (91% w/w), 12 ml water, 75 ml HCl (31% w/w, technical grade) were combined in a beaker and chilled to 0 C. Bright yellow
beta-nitro-3,45-trimethoxystyrene was ground with mortar and pestle until finely powdered. Dull gray zinc powder, 400 mesh, was ground with mortar and
pestle until absent of clumps.
The beaker was placed on salt water bath and 2.40 g nitrostyrene was added in one portion and stirred until nearly dissolved, although some small
particles of nitrostyrene would not dissolve. In 10 equal portions spaced 5-6 minutes apart, 13.0 g of zinc was added to the stirred contents of the
beaker. Reaction temperature was <10 C at all times despite exothermic activity and effervescence.
The reaction was left to stir for an additional 7-8 hours with reaction temperature <10 C. By hours 2-3 of the 7-8 hours of stirring there was no
indication of any unreacted yellow nitrostyrene. By the final hours of stirring there was almost no trace of undissolved zinc powder. The unfiltered
contents of the beaker, clear and gray in color, were made distinctly basic with 70 g NaOH in 70 ml water while maintaining a reaction temperature
<20 C. A large amount of white salts formed in the aqueous layer and the alcoholic layer took on an amber color.
The mixture was stirred for several minutes and then the alcoholic layer decanted. The aqueous layer was extracted/decanted twice more with IPA, the
final extraction/decanting being clear in color. The alcoholic extracts were left to sit in a freezer overnight, then dried over MgSO4 and filtered to
yield a crystal clear light yellow solution. This was then made acidic with alcoholic H2SO4 to pH = 6 to 7, with the crystal clear light yellow
solution turning more turbid and amber colored as the crystals precipitated. The sulfate salt of the amine was freeze precipitated overnight, vacuum
filtered, and washed with acetone to yield 0.60 g (~20% yield) of the white and shiny sulfate salt. The filtrate was chilled to -15 C but no
additional crystals were precipitated. |
This procedure was run on the basis of persona's work, which claims yields of ~75%. See http://www.sciencemadness.org/talk/files.php?pid=603835&... Persona's work was, in turn, based on Leminger's work, see https://erowid.org/archive/rhodium/chemistry/leminger.html
To be short and to the point, I'm not sure what went wrong. The nitrostyrene is recrystallized once and bright yellow in color, free of any
degradation or polymerization. The zinc is advertised as 99.9% purity. While the zinc was not activated (i.e. not washed with dilute HCl to make it
bright and shiny) I don't see how this would matter as it reacts with a very large excess of HCl in situ. Temperature control was reasonable at all
points of the reaction and zinc addition was as prescribed.
Does anyone with a more thorough understanding of this reaction have any input? Would it be beneficial to run it as Leminger describes it, forming an
IPA/HCl solution and then adding nitrostyrene and HCl in alternating batches, to maintain constant ratios? I have noticed one paper (DOI:
10.1055/s-0034-1379481) goes so far as to add the HCl in portions, as well.
I have also read of some using an even greater excess of NaOH to fully re-dissolve the zinc salts. But I assume this is for ease of workup: filtration
and extraction with separatory funnel rather than decanting. Zinc salts would not somehow complex with the freebased amine, correct? I'm also confused
by some write-ups mentioning the freebased amine floated on top of the milky white solution formed subsequent to addition of base. In this trial, it
was observed as an amber alcoholic layer clearly separated from a lower aqueous layer containing zinc salts. The amine was dissolved in the amber
layer, not floating atop it.
[Edited on 13-11-2019 by horribilis]
[Edited on 13-11-2019 by horribilis] |
