Organic compounds that react with carbonate ions I want to remove carbonate ions from dissolved potassium carbonate (potash) by letting an organic compound react with the carbonate ions. I don't have a very good knowledge of organic chemistry, but are there certain types of organic molecules that can react with these carbonate ions to form new compounds?

Additionally, are there reactions in which the carbon atom from the carbonate ion can be inserted into the main carbon chain of another organic compound (making, for example, propane from ethane)?
Cook it up with ethylenediamine or diethylenetriamine- but don't bet on it.  What do you plan to have as the counterion for $\ce{K^+}$?  Check your carbon oxidation states for the second half of your question.

No, wait!  Add citric acid.  Yeah, that's the ticket.  Plop, plop, fizz, fizz.