organometallic
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What have I created??
I think I accidentally made a polymer..
During an esterification reaction, my low yeilds led me to try and drive the reaction forward by removing water. The reaction vessel was placed in
~150 degree water bath. A colourless distillate was collected, which came over at 104 degC. The substances in the boiling flask were: Acetic acid (BP
118), benzyl alcohol (BP 205), benzyl acetate (BP 212) , water (BP 100), sulphuric acid (91%) (BP 338degC).
The product, after an hour of distillation using a standard setup, was a yellow-cream goo, which hardens when cooled to room temperature and attains
the consistency of freshly-chewed chewing gum when warmed to 70 degC. CHEWING GUM!?!?? What I hypothesize happened is that the acetic acid in fact
formed an azeotrope with the water produced by the reaction, which then boiled at a lower temperature. The sulphuric acid which was used as a catalyst
then hydrolysed the benzyl alcohol into some bizarre polymer? Maybe?
Someone, tell me whats going on..
[Edited on 4-8-2007 by organometallic]
[Edited on 4-8-2007 by organometallic]
In vials of ivory and coloured glass
Unstoppered, lurked her strange synthetic perfumes,
Unguent, powdered, or liquid - troubled, confused
And drowned the sense in odours.
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kmno4
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Indeed, BzOH polymerise in H2SO4.
Besides, CH3COOH and H2O do not form azeotrope.
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organometallic
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Yay! I was right..okay, thanks for the help. How ought I go about breaking this polymer into monomer units? At the moment, it is rendering my
round-bottomed flask useless. Would neutralizing the excess acid with sodium hydrogencarbonate followed hydrolysis (addition of water and heating to
reflux) work?
In vials of ivory and coloured glass
Unstoppered, lurked her strange synthetic perfumes,
Unguent, powdered, or liquid - troubled, confused
And drowned the sense in odours.
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kmno4
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This "polymer" contains ...-PhCH2-PhCH2-... units. It is rather polycondensate not polymer. It cannot be depolymerised back to BzOH. Just trash it -
it is usless. This "thing" is soluble in ksylene, toluene, etc... especially hot.
[Edited on 4-8-2007 by kmno4]
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garage chemist
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You should neutralize the acid before distillation, otherwise it will act upon your ester and alcohol in the way you have seen. Sodium acetate will do
very well as a base and not hydrolyze your ester.
You can still remove the water by distilling it off during the reaction, but take care not to heat the flask too strong. Before distilling the ester
for workup, neutralize.
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organometallic
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"You should neutralize the acid before distillation, otherwise it will act upon your ester and alcohol in the way you have seen. Sodium acetate will
do very well as a base and not hydrolyze your ester.
You can still remove the water by distilling it off during the reaction, but take care not to heat the flask too strong. Before distilling the ester
for workup, neutralize. "
Thanks. I'll try that and post a write-up here in a few days time. 
Thanks kmno4, i'll dissolve the gunk in toluene.
In vials of ivory and coloured glass
Unstoppered, lurked her strange synthetic perfumes,
Unguent, powdered, or liquid - troubled, confused
And drowned the sense in odours.
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