Pyridine Alternative

Rob

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Mar 1, 2003, 5:23:46 PM3/1/03

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Anyone recommend a good alternative to pyridine as a reaction solvent?
The pyridine in the reaction I have is used to mop up HCl from reaction of
an acid chloride with polyvinyl alcohol.

Thanks.

Rob.

Ron

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Mar 1, 2003, 6:26:56 PM3/1/03

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"Rob" <forn...@yahoo.co.uk> wrote in message
news:Spa8a.5835$p17....@news-binary.blueyonder.co.uk...

> Anyone recommend a good alternative to pyridine as a reaction solvent?
> The pyridine in the reaction I have is used to mop up HCl from reaction of
> an acid chloride with polyvinyl alcohol.
>

Question is a bit thin on data. Some more would be useful!...
Why change solvent if it works?
Do you want another basic solvent?
Higher/lower boiling?

--
Ron Jones

Don't repeat history, see unreported near misses in chemical lab/plant at
http://www.crhf.org.uk

Uncle Al

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Mar 1, 2003, 7:23:09 PM3/1/03

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You don't need it as a solvent, you only need it as a cheap chemically
inert proton base of modest pKa and low equivalent weight. Add 1.2
equivalents in another solvent. Or chuck in an N-alkylimidazole or
dimethylaniline (yeah, that's an improvement) instead. You might even
get away with micronized sodium carbonate (Aldrich, for doing
Williamson syntheses).

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!

Muhammar

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Mar 1, 2003, 10:46:05 PM3/1/03

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Try dimethylacetamide or N-methylpyrrolidine. If your PVA does not
dissolve, add some LiCl and increase the temperature. You should still
have some base around, as the basicity of these solvents may not be
good enough. So I would add some pyridine (or DMAP), 1-2 eq. per acyl
chloride.

What kind of acyl groups do you have to attach? Can you use anhydride?
- this might be a cleaner acylation reaction, and you could skip the
stoechiometric ammount of base.

Muhammar

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Mar 2, 2003, 3:58:50 AM3/2/03

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Should have been NMP, N-methylpyrrolidinone. Sorry for the typo.

muha...@hotmail.com (Muhammar) wrote in message news:<a6cffac9.03030...@posting.google.com>...

Rob

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Mar 2, 2003, 5:01:49 AM3/2/03

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The reaction uses cinnamoyl chloride at 50C with PVA.
It is a tried and tested product but I would like to use a solvent of lower
odour & hazard properties if possible.

Thanks,
Rob.

"Ron" <r...@ronjones.org.uk> wrote in message
news:104656121...@doris.uk.clara.net...

Uncle Al

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Mar 2, 2003, 11:43:28 AM3/2/03

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Would urea be a strong enough base to scavange HCl but still be
resistant to acylation? Urea would aid in solubilization of the
polymer, too, by disrupting intramolecular hydrogen bonding.

Muhammar

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Mar 2, 2003, 11:41:29 PM3/2/03

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Vinyl cinamate is commercially available. It is expensive: 500mL/$200
(TCI-US), but the price may come down grat deal if manufactured in
bulk. It would be cleanest way - no waste, no solvents, you can do
these polymerizations in water slurry. The only trouble would be buy
the monomer for a reasonable price and get the right degree of
polymerisation. And, your product would have 100% cinnamoyl
substitution. (Usualy is it is difficult to get 100% of all -OH
covered, plus there can be some residual acetyls in the starting PVA)

If you stil like to go with PVA acylation, I would also consider
N-methylimidazole (2 eq. per cinamoyl chloride) and go with
Dimethylacetamide or NMP (with some dissolved LiCl). The toxicity and
odour of these solvents is not too bad - but it will be hard to
recycle them.

ppati...@gmail.com

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Aug 23, 2017, 9:41:30 AM8/23/17

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Dear Rob

You may take reaction in dichloromethane & triethylamine Mixture.

Thanks

Angelo

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Aug 25, 2017, 1:22:58 PM8/25/17

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Good advice. In general, tertiary amines (R3N) work well in that job for
(1) they are all basic (capturing HCl) and (2) normally incapable of
undergoing acylation or similar electrophylic reactions like sulfonation
etc.
They are nucleophylic, and good ones also, but the reversible adduct they
initially form with electrophylic species (acyl chloride), i.e.
R'CO(-)Cl-N(+)R3, is not capable (if temp is not raised enough) of
eliminating HCl through a beta-H in their R groups (if present).
This leaves room for the nucleophyle of interest to react with the acyl
chloride (or the adduct, products will be the same).
So, to possibly avoid such complications, it is reasonable to choose an
amine not possessing beta-hydrogens.
To this end pyridine is optimally suited. The cited dimethyl aniline is
also good, though less resistant to an oxidative attack (if any) in the
aromatic ring.
In this respect N-methyl imidazole is better.
Trimethylamine has the only inconvenient that it is gaseous.
If the chosen amine has beta-hydrogens and the temperature has to be high
it is not advisable to use an excess of it: the part of it in excess acts
as a base to the said adduct favoring HCl elimination as a side reaction.

> Thanks

regards
Angelo