Does Aspirin React with NaOH? | C9H8O4 + NaOH Reaction Explained

[tgt]

Homework Statement

Does this reaction occur?

Aspirin = C9H8O4 (numbers are meant to be subscripts)

Aspirin + NaOH => what?

The Attempt at a Solution

Aspirin + NaOH => 9 carbon dioxide + 4 water molecules + 9 hydrogens (i.e H2)

 

[Borek]

No. You have to look at the structure of aspirin, using just overall formula will lead you nowhere.

 

[symbolipoint]

Homework Statement

Does this reaction occur?

Aspirin = C9H8O4 (numbers are meant to be subscripts)

Aspirin + NaOH => what?

The Attempt at a Solution

Aspirin + NaOH => 9 carbon dioxide + 4 water molecules + 9 hydrogens (i.e H2)

The empirical formula for Aspirin is not exact enough; you want to know that Aspirin is acetyl salicylic acid. (or is it three separate words, "acetylsalicylic acid ?")

 

[tgt]

The structure is here http://en.wikipedia.org/wiki/Aspirin

Then how does it react? I have no idea. This problem came up in a stoichiometry problem.

 

[Borek]

Read the wikipedia article, it clearly states what should happen when you put aspirin in NaOH solution.

 

[lesieux]

Aspirin has got a carboxyl group -COOH and an ester group -CO-OCH3 (acetyl); the first function reacts as an acid and becomes -COO-, the second function overcomes saponification RCOOR' + OH– -> RCOO– + R'OH

 

[symbolipoint]

Aspirin has got a carboxyl group -COOH and an ester group -CO-OCH3 (acetyl); the first function reacts as an acid and becomes -COO-, the second function overcomes saponification RCOOR' + OH– -> RCOO– + R'OH

Would the saponification reaction be a much slower reaction, possibly relying on more extreme conditions other than moderate concentrations at room temperature?

 

[Borek]

Aspirin in basic solution hydrolises quite fast. Fast enough that it will at least partially hydrolise during standard titration with base, giving unreproducible results.

 

[lesieux]

That is the reason for you need to use an excess of sodium hydroxide (at high temperature to ensure that all the aspirin reacts) to titrate aspirine and then, in a second step, titrate the excess of sodium hydroxide. But you will have to consider that one mol of aspirin reacted with two moles of base in your calculation.

 

[Borek]

That's right, backtitration is the usual approach.