[shusson]

I am following a published procedure for deprotecting a tert-butyl ester using trifluoroacetic acid. Following removal of the t-butyl group, the product was precipitated in ethyl ether, re-dissolved in water, and stirred with Amberlite IRA-400(OH) ion-exchange resin at 0C for 30 minutes. Can anyone tell me the likely purpose of the ion-exchange resin?

[Babcock_Hall]

Think about the product after tert-butyl protection and the identity of the counterion.  Can you disclose the identity of the product?

[shusson]

The product is 2-((2-hydroxy-3-(methacryloyloxy)propyl)dimethylammonio)acetate.

The precursor is N-(2-tert-butoxy-2-oxoethyl)-2-hydroxy-3-(methacryloyloxy)-N,N-dimethylpropan-1-aminium iodide

See attachment

[Babcock_Hall]

So after treatment with the ion-exchange resin, you now have a zwitterion (neutral), and you no longer have the iodide ion.  I would think that getting rid of iodide might be helpful in some applications, and the zwitterion might crystallize out.  That is just speculation on my part.