h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Are salicylate and salicylic acid the same thing?

Salicylate is the salt of the salicylic acid, the hydrogen ion (which makes it acid) is replaced by another positive ion, like sodium, potassium or something.

same with any acid.

Acetic acid when made into a salt is acetate

carbonic acid becomes carbonate.

Sulphuric acid becomes sulphate

phosphoric acid becomes phosphate...

I'm trying to understand if these two sentences are correct (at least the first one is but I'm not sure about the second).

"Kiwifruit contain high amounts of salicylates (the substance used to make aspirin) and care should be taken by people affected by them."

"Kiwifruit contain high amounts of salicylic acid (the substance used to make aspirin) and care should be taken by people affected by it."

I guess what I am asking is given that kiwifruit contain salicyates, do they also contain salicylic acid?

yes because they are just different forms of the same compound.

The use of the word 'them' I think is because they are talking about salicylate and aspirin - which are not the same thing (although very close. Aspirin is methyl salicylate.

Or to put it another way it is not possible to have salicylate without having salicylic acid in a water solution (which it is both in us and a kiwi fruit).

Salicylate will remove a proton from water to form salicylic acid.

Salicylic acid will donate a proton to water to from salicylate.

These two processes happen at the same time until they reach an equilibrium point.

It's in a guide entry I'm working on. I want to avoid the first one because of the ambiguity about 'them' More to do with salicylates and kiwifruit than salicylates and aspirin though. I hadn't thought of that

>>
Salicylate will remove a proton from water to form salicylic acid.

Salicylic acid will donate a proton to water to from salicylate.

These two processes happen at the same time until they reach an equilibrium point.
<<

Nice explanation, thanks. In something like a fruit, is that process of reaching equilibrium ongoing as the fruit ripens?

It doesn't happen slowly, it happens more or less instantaneously. Acid-base reactions like that are about the fastest chemical reactions there are.

So ripening has nothing to do with this process.

Ok, if it's a static thing i.e. once the reaction has happened then it's stable, which is it that is in a mature kwifruit?

Oh it's not static, it's a dynamic equilibrium which means it goes forward as quicky as it goes back and so it just looks stable.

I don't know what you mean by that question to be honest. To my mind you are asking is there more salicylate in mature fruit than in unripe fruit?

Good, that's what I thought (that it's dynamic).

I just thought the ripening (or aging) process might have affected or been affected by the reactions to and from the different forms.

So would it be true that at any one time there are both salicylic acids and salicylates in a kiwifruit? And that they are in constant rearrangement chemically, with each other?

Yes

"Acetic acid when made into a salt is acetate

carbonic acid becomes carbonate.

Sulphuric acid becomes sulphate

phosphoric acid becomes phosphate..."

...and hydrochloric acid becomes chloride.

B

Ah but's that's not an oxide

The highest oxide is 'ate' the next is 'ite' and then it gets silly with things like hypo...ite etc.

It's not too IUPAC but it works well enough most of the time.

You're right though, I shouldn't have said 'any' acid. Just most.

I don't recall you saying anything about oxides before. Just salts...

B

'Aspirin is methyl salicylate'.

Aspirin is acetyl salicylate, where the -OH group of 2-hydroxybenzene is esterified.

Methyl salicylate is 'oil of wintergreen' (germolene etc) where the acidic group of hydroxybenzoic acid is esterified.