what is soda lime for in decarboxylation of a benzoic acid and salicylic acid?Theoretic - 23-1-2004 at 07:23
Now, I think this belongs in the Beginnings section. The soda lime is actually the thing that decarboxylates the acid.guaguanco - 23-1-2004 at 09:46
Quote:
Originally posted by Theoretic
The soda lime is actually the thing that decarboxylates the acid.
I suspect that the advantage of using a Calcium or Sodium salt is the increased melting point. Calcium would also have a natural affinity for CO2.Theoretic - 23-1-2004 at 10:35
"Calcium would also have a natural affinity for CO2."
Yes, and so does NaOH, which is the second component of soda lime.
"is the increased melting point."
Of what? Decarboxylation isn't done at temperatues around NaOH's mp, if that's what you mean.guaguanco - 23-1-2004 at 11:01
Well, I could be all wet.
I speculate that heating Sodium Benzoate would allow the temperature to rise past the MP/sublimation point of benzoic acid. There's also probably
some thermodynamic advantage that allows the COO(-) moiety to hop to the metal cations. But I have no facts in front of me to support this...Al Koholic - 24-1-2004 at 06:19
I would speculate that since the oxygen involved in the CaO molecule is highly electron dense, these electrons will attack the exposed and highly
electron deficient carbon atom of the carboxyl group.
Now that I think about this more, the Ca shouldn't change oxidation state much at all in this reaction being basically stripped of electrons
while bonded to O anyway. The O in this bond will become reduced even further though because it is entering into a carbonate anion which will
increase the density of electrons around the oxygen atoms even further.
The benzene ring is gaining electron density and so is definetly reduced and must function as an oxidizing agent in the reaction. The reducing agent
then I would have to say is the carbon in the carboxyl group being as oxidized as it can possibly be at the end of this transformation. Perhaps I was
wrong is assuming that the Ca doesn't change oxidation states much and actually functions as a reducing agent as well, being oxidized further
upon entry into the carbonate complex...
