Keras
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benzyl alcohol + sulphuric acid = ?
I just happened to let a few drop of 95/96% concentrated sulphuric acid fall into a small grad tube with a bit of benzyl alcohol in. It immediately
gave rise to a sort of brown compound. Any idea what that can be? Some sort of ether, or an ester?
Just curious if anyone has an idea.
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Syn the Sizer
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Is it possible that it is benzyl sulfate? I was at first thinking of a dehydration but I am sure that wouldn't work with benzyl alcohol.
[Edited on 3-4-2020 by Syn the Sizer]
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DraconicAcid
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Adding sulphuric acid to benzyl alcohol is going to give you benzyl cations (at least in low concentrations). This could react with the alcohol part
of other benzyl alcohol molecules to give an ether, but it could also do a Friedels-Craft alkylation to put the benzyl group on the o/p position of
another ring. If that happens on the ortho position, it could do it twice to give you dihydroanthracene.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Sigmatropic
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Probably similar to what happens to paramethoxybenzyl protecting groups during the deprotection under extremely acidic conditions (neat
trifluoroacetic acid sometimes with catalytic triflic acid).
It polymerizes by FC alkylation forming a very apolar and strongly colored polymer.
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TheMrbunGee
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And when equal volumes of liquids are combined in a test tube, the reaction is explosive, polymer formed is quite hard to wash off all kinds of
surfaces. Thankfully sulfuric acid seemed to be consumed by reaction, because no organic fabrics were damaged around splashes (the sulfuric acid way).
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Keras
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Yeah, it was a bit of a pain to wash the polymer off. Since I was doing the experiment in a TPX grad cylinder, I was a bit nervous to use a piranha
solution, lest the cylinder would be dissolved with the rest. I tried sodium percarbonate + sulphuric acid (r.t.) and it produced some sort of nasty
brownish compound with fortunately I was able to dilute with acetone, and finally I got my cylinder back clean and intact.
Thanks for suggesting FC alkylation. I hadn't even thought about that. Has the -CHâ‚‚OH group a directive effect? Logically, the C is slightly
positive, so this should induce a negative charge in ortho/para positions, no?
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unionised
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benzyl alcohol + sulphuric acid = tar.
[Edited on 3-4-20 by unionised]
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Metacelsus
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Ah yes. Tar, the organic chemist's constant companion.
I posted a few minutes ago that I missed working on fluorophore synthesis. But I definitely won't miss the tar! (Even successful reactions with 90%
yield gave brown gunk as the crude product. The other 10% was "tar".)
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Keras
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Quote: Originally posted by Metacelsus  |
Ah yes. Tar, the organic chemist's constant companion.
I posted a few minutes ago that I missed working on fluorophore synthesis. But I definitely won't miss the tar! (Even successful reactions with 90%
yield gave brown gunk as the crude product. The other 10% was "tar".) |
Yet coal tar is such a bountiful source of useful reagents!
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Cou
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Sometimes when doing fischer esterifications, the reaction mixture turns brown due to reaction of sulfuric acid with organic impurities.
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