Aspirin + NaOH

[Rob]

OK, a titration question for you here:

 

"In order to determine the aspirin content of a commercial aspirin tablet, a tablet weighing 0.400g was dissolved in aqueous ethanol and titrated with 0.100M NaOH solution: 16.7cm^3 of the NaOH was required to reach the end point. Under the conditions of the titration, only the Carboxylic acid group reacts with the NaOH".

 

Obviously, the question goes on to ask about moles in the aspirin, and the % by mass of aspirin in the tablet, but what I need to know is what is the balanced equation for this reaction?

 

NaOH + COOH -> ?

 

Cheers, Thanks for your help.

[Fuzzwood]

COOH is an acid group. HCl + NaOH gives water and NaCl, H₂SO₄ + 2 NaOH gives 2 water + Na₂SO₄

 

COOH + NaOH --> water and ???

[Rob]

Well, I though NaCO3, but something in the balancing didn't seem to add up

[Melvin]

It would probably just react to give the salt of sodium and aspirin (sodium acetylsalicylate?)

 

NaOH + CH3COOC6H4COOH --> CH3COOC6H4COONa + H2O

 

I would think the NaOH would break apart the ester though (to sodium acetate and sodium salicylate)

[Fuzzwood]

Yeah, because aspirin is of course a lot more than just COOH, like Melvin stated.

[hermanntrude]

It would probably just react to give the salt of sodium and aspirin (sodium acetylsalicylate?)

 

NaOH + CH3COOC6H4COOH --> CH3COOC6H4COONa + H2O

 

I would think the NaOH would break apart the ester though (to sodium acetate and sodium salicylate)

 

however, the question explicitly states that ONLY the COOH group reacts with the NaOH at the conditions of the titration.

[Rob]

Its OK guys, don't fret too much any more -

 

NaOH + COOH -> COONa + H2O

[hermanntrude]

Its OK guys, don't fret too much any more -

 

NaOH + COOH -> COONa + H2O

 

well done. that's the reaction they're expecting you to work with

[Acs]

It states "only the COOH group reacts with the NaOH" because the Acetyl group also reacts with it naturally, which forms sodium acetate (as far as I'm concerned) besides the sodium salicylate, which makes the whole reaction a 1:2 ratio in regards to Aspirin : NaOH. But when only the COOH group reacts with it as the task says, you don't have to take the Na-Acetate part into consideration, the ratio of the reactants are 1:1 I suppose, resulting in: C₈H₇O2COOH + NaOH = C8H7O2COONa + H2O.

[peterwlocke]

NaHO3 plus H2O

Edited April 17, 2019 by peterwlocke

[MigL]

I just take my aspirin straight, without the caustic.
Less stomach ulcers that way.