Niklas
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Synthesis of 4-(N,N-Dimethylamino)-beta-nitrostyrene
Greetings once again, I‘ve recently read about 4-(N,N-dimethylamino)-beta-nitrostyrene, I‘ll just abbreviate it as DMANS in the following, and it
potentially being an easy to prepare solvatochromic dye [1].
Fig.1: The two resonance structures most likely responsible for the solvatochromic properties of DMANS
With it being a beta-nitrostyrene, and the corresponding benzaldehyde, 4-(N,N-dimethylamino)benzaldehyde, or DMABA for short, being commercially
available, it only seems logical to go for a Henry reaction with Nitromethane to achieve its synthesis.
Fig.2: Synthesis of DMANS using a Henry reaction
All reagents used in the following preparation were purchased from reputable sources such as Merck and S3 Chemicals. The nitromethane was previously
prepared in 33,4% yield by decarboxylation of sodium nitroacetate generated in-situ from sodium chloroacetate and sodium nitrite according to [2].
Fig.3: Synthesis of nitromethane by decarboxylation of sodium nitroacetate
Synthesis of 4-(N,N-dimethylamino)-beta-nitrostyrene, DMANS:
In a 50 ml RBF, equipped with an allihn condenser an magnetic stirring, 1,59 g nitromethane (26 mmol) and 0,3 g ethylene diamine (5 mmol) were
dissolved in 20 ml of isopropanol. To this 2 ml of glacial acetic acid (34,9 mmol), the exact quantity doesn’t really matter, was dropwise added
under constant stirring over the course of one minute, causing some solids to precipitate, which quickly dissolved again.
Fig.4: The reaction mixture at this stage of the synthesis
To the now clear, very slightly yellow solution, 2,98 g (20 mmol) of solid 4-(N,N-dimethylamino)benzaldehyde was added in multiple smaller portions,
to avoid interrupting the stirring. During this step the mixture quickly took on a dark yellow color, having turned increasingly more red towards the
end of the addition.
Fig.5: The reaction mixture towards the end of the DMABA addition
The mixture was now heated to a mild reflux with the help of a heating block, and kept refluxing over night resulting in a total reaction time of
approximately 12 hours. Just a few minutes into the heating some lustrous red flakes already started precipitating, consisting of the desired
4-(N,N-dimethylamino)-beta-nitrostyrene.
Fig.6: First precipitation of the product while refluxing
The next day the heating was stopped, and the now garnet reaction mixture was dumped into three equal parts of destilled water, followed by removal of
the solids by vacuum filtration and drying on the pump to yield somewhat dry flakes of crude product.
Fig.7: Crude flakes of DMANS
For further purification this residue was recrystallized from boiling isopropanol, resulting in the formation of gorgeous orange flakes with an
intense crimson shine, which again were collected by vacuum filtration and air dried until constant weight.
Fig.8: Recrystallized DMANS
Yield: 3,06 g ; 79,63%
While this yield is rather satisfactory, the presumed solvatochromic properties unfortunately really aren’t. After dissolving 3,0 mg if DMANS in 5
ml water, n-hexane, DMSO, IPA, DCM and GAA each, it could only produce a very small color spectrum in the yellow to orange range, which may just seems
like different dilutions in the same kind of solvent to an unknowing person overall.
Fig.9: Solutions of DMANS in IPA, DCM and DMSO
Literature:
[1] https://www.sciencedirect.com/science/article/abs/pii/S10106...
[2] http://orgsyn.org/demo.aspx?prep=CV1P0401
[Edited on 14-8-2024 by Niklas]
[Edited on 15-8-2024 by Niklas]
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RustyShackleford
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terrible post but cool setup. Is that all in a professional setting or do you own all that fancy stuff? I'm jealous of the reactor and heating mantle.
[Edited on 14-8-2024 by RustyShackleford]
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Niklas
Hazard to Self
Posts: 50
Registered: 1-12-2023
Location: Germany
Member Is Offline
Mood: Polymerized
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@RustyShackleford Sorry, I accidentally published the unfinished writeup, no wonder it was terrible xd
It is indeed my privat laboratory at home, managed to get hold of this reactor and a 3 l version for free a while back, and the heating block was
purchased from Synthware.
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