NaHCO3 and aspirin.

josephcollins

Hi ppl,
I was wondering could someone help me with this explanation. Why does the addition of Sodium Hydrogencarbonate help an aspirin to dissolve. In tablets of aspirin, acetylsalicylcic acid is mixed with sodium hydrogencarbonate and when the soluble aspirin tablet is dissolved in water the acetylsalicylcic acid and the sodium hydrogencarbonate react together.

Thanks a lot,
joe

movies

In aqueous solution the basic NaHCO3 can deprotonate the acidic acetylsalicylic acid. The resulting charged species (carboxylate anion) is very soluble in water.

Without the base then the acid would be protonated and therefore uncharged. The rest of the molecule is rather non-polar and thus not very soluble in polar solvents like water.

chem_tr

As Movies explained the issue well, I will only give the reaction scheme.

[tex]HSal + NaHCO_3 \longrightarrow Sal^- Na^+ + CO_2 + H_2O[/tex]

Normally, H₂CO₃ is expected to be formed, but is very unstable to yield carbon dioxide and water for lower energy and higher unregularity (entropy) needs.

quality68

It's very similar to that between benzoic acid and sodium hydrogencarbonate.

C6H5COOH + NaHCO3 -----> C6H5COONa + CO2 + H2O
NaHCO3