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Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: Sharadleedskem on May 04, 2015, 06:49:55 AM

Title: Preparation of Phase Transfer Catalyst
Post by: Sharadleedskem on May 04, 2015, 06:49:55 AM
I have tried preparing  Tetrabutylammonium acetate by using Tetrabutylammonium bromide and Acetic acid but could not get anything . This was planned on the basis as I had prepared Tetrabutylammonium hydrogen sulfate using TBAB , Butanol and Sulfuric acid where I could get the product . So any body knows how I can obtain Tetrabutylammonium acetate ?
Title: Re: Preparation of Phase Transfer Catalyst
Post by: discodermolide on May 04, 2015, 07:23:54 AM
Try an ion-exchange resin?
http://www.bio-rad.com/webroot/web/pdf/lsr/literature/9114_AG_1.pdf (http://www.bio-rad.com/webroot/web/pdf/lsr/literature/9114_AG_1.pdf)
Title: Re: Preparation of Phase Transfer Catalyst
Post by: Sharadleedskem on May 04, 2015, 07:29:04 AM
Quote from: discodermolide on May 04, 2015, 07:23:54 AM
Try an ion-exchange resin?
http://www.bio-rad.com/webroot/web/pdf/lsr/literature/9114_AG_1.pdf (http://www.bio-rad.com/webroot/web/pdf/lsr/literature/9114_AG_1.pdf)

Thanks , will try.
Title: Re: Preparation of Phase Transfer Catalyst
Post by: Dan on May 04, 2015, 09:09:54 AM
Bear in mind that TBAOAc is extraordinarily hygroscopic. It may be difficult to prepare in dry, crystalline form.
Title: Re: Preparation of Phase Transfer Catalyst
Post by: clarkstill on May 04, 2015, 10:07:47 AM
A pKa issue? Presumably you're relying on formation of HBr as a by-product, but this is a much stronger acid than the AcOH you are trying to exchange. Sulfuric is quite a bit more acidic than AcOH (-3 vs 5), but still quite a way off the pKa of HBr (-8ish) though, so not sure this is a very good explanation. I know virtually nothing about this kind of ion exchange stuff though, so perfectly willing to be shouted down on this one!

I think a method people use for these types of exchange is to make the silver salt of the acetic acid. Then after salt metathesis the AgBr precipitates out, and you don't have to rely on thermodynamics/pkas any more.