In the esterification reaction that I work on, HCl is produced.Adding base ruins the expected product since it reacts with the initial materials and forms a red byproduct. The bases that I tried are pyridine, DMAP, Triethylamine and also NaHCO3. but all had unwanted byproducts. Would you suggest a way to get rid of acidic pH for progression of the reaction? Do you think putting base on the top of reaction vessel on a filter paper without contact with reaction medium remove all the produced acid?
Well, you need a very sterically hindered base for this, like DiPEA or DBU. They were designed to minimize basic interaction with substrate while keeping the basic properties. You can try your variant with base "on top", but the problem is that gaseous acid does not react that fast and it is quite soluble in most solvents.
You can try polymer-immobilised tertiary bases, they sometimes help.
I had a thought about this problem once but never got to try it as hindered bases worked and we didn't have right materials. Lead acetate is moderately soluble in some polar solvents, so it could be used to increse the pH as lead chloride is generally insoluble. Maybe some other salt could do (do not forget that they are toxic). Or some metal, like powdered iron, could react with it, but that could lead to reacive spieces, so it needs more thought.
Why cant you just add water and organic solvent and extract your ester into organic layer?
There are basically two ways of looking at your problem.
(a) Suggesting a solution based solely on your statement, that is, a solution for removal of generated HCl without the usage of a base.
(b) Look at the problem from an all together different angle.
You have already got quite a few good suggestions earlier in this discussion from HCL removal point of view.
I would like to look at the problem from (b) point of view.
There are quite a few other methods of esterification. Please check them from a the books: (1) Vogel's Practical Organic Chemistry (b) Organikum.
Transesterification under acidic/neutral conditions may help.
I am not sure whether usage of the alkyl chloroformate method will be of any help. Please do check.
With best wishes.
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