Fery
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benzil by oxidation of benzoin with NH4NO3 catalyzed by Cu(II) acetate
Reactants:
0,040 g Cu (II) acetate dihydrate (catalyst)
3,72 g benzoin (17,5 mmol) Molar mass 212.24 g/mol https://www.sciencemadness.org/whisper/viewthread.php?tid=68... (I used that second grade crop after using 1,00 g for benzoinoxime https://www.sciencemadness.org/whisper/viewthread.php?tid=15...)
1,9 g NH4NO3
10,0 g acetic acid
2,0 g H2O
All reagents were added into 250 ml reaction flask and reflux condenser attached.
Heated on oil bath, occasionally shaking, N2 bubbles evolution observed already when oil bath 80-110 C, everything dissolved smoothly, then reflux
totally for 1,5 h, oil bath temperature 150 C.
(I overkilled the size of the reaction flask, I used 250 ml because I was afraid of gas evolution, but 100 ml flask should be fine, maybe even 50 ml,
the evolution of N2 was not vigorous, this could depend on the amount of the catalyst.)
Cooled to room temperature and then to +4 C outside (winter temperature).
Vacuum filtered on sinter, washed with distilled water on sinter, sucked to dryness, air dried for 2 days, last day no more weight decreasing
observed.
Yield 3,35 g = 15,9 mmol (91%) of nice yellowish crystals. Molar mass 210.232 g·mol−1.
m.p. 95,0-96,0 C (lit. 94.0 to 96.0 °C https://en.wikipedia.org/wiki/Benzil)
some further experiments starting from benzil (phenytoin, benzilic acid rearrangement, benzil dioxime = Ni(II) indicator)
https://www.sciencemadness.org/whisper/viewthread.php?tid=15...
https://www.sciencemadness.org/whisper/viewthread.php?tid=19...
https://www.sciencemadness.org/whisper/viewthread.php?tid=19...
Attachment: vogel_benzil.pdf (136kB)
This file has been downloaded 166 times
reagents from the left: copper (II) acetate dihydrate, benzoin, NH4NO3, acetic acid
after adding everything into reaction flask (smaller flask should be used, N2 evolution slow enough)
after reflux
after cooling down to +4C
vacuum filtered on sinter
nice pale yellow crystals of the product (I like such synthesis where recrystallization not necessary, here the crystallization happened directly from
the reaction mixture, according Vogel recrystallization does not change m.p., the product is already pure enough)
[Edited on 7-12-2021 by Fery]
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Bedlasky
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Hi, Fery, very nice description! Do you have some plans with your benzil?
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karlos³
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Mood: oxazolidinic 8)
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Uh thats nice and surprisingly simple, while I also still have lots of benzoin.
The benzil even has the nice neon-greenish colour as a liquid I know from other alpha-diketones like 1-phenyl-1,2-propanedione and
1-phenyl-1,2-hexanedione.
Are you going to aminate it, for ephenamine for example?
Alpha-diketones are really nice to make 1,2-aminoalcohols from via reductive amination, they will selectively aminate only on one carbonyl.
[Edited on 11-12-2021 by karlos³]
verrückt und wissenschaftlich
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Fery
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Hi Bedlasky and karlos³
these 3:
phenytoin (reaction with urea)
benzilic acid (rearrangement with alkaline hydroxide)
diphenylglyoxime (reaction with 2 moles hydroxylamine) this is Niclon indicator, analogue of dimethylglyoxime, it does not have any advantage over
commonly used dimethylglyoxime, I just want to see its color with Ni(II)
Boffis if you are reading this, you can try the same with the 2,2'-furoin and 2,2'-pyridoin you synthesized (the first link in my first post).
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Boffis
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Hi Fery, Nice work and a good write-up.
I have run this reaction myself but never seem to have posted it. It works well with Benzoin, reasonably with furoin but fails with pyridoin.
I tried nitric acid on pyridoin as in Vogels procedure for the nitric acid oxidation of benzoin to benzil but the reach is very vigorous and difficult
to control. More dilute nitric acid may work better as when the first ml or so of nitric acid is added a yellow product is formed that later
dissolves. When only half the nitric acid has been added oxidation appears complete and every thing dissolve. Neutralisation ppt only a little red
powder.
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