[Cleoleo]

The question was show the effect of excess alkali on the molecule.

I understand the -OH becomes O- becomes the phenol acts as an acid and the NaOH as a base but HO3S is also an acid, but I didn't realise this and thought they'd be no effect.

What indication is there that this acts as an acid like the -OH group ?

Thanks alot

[katyness]

I used to draw the Lewis structure and see what charge it was yield and then decide.

[illusionz]

(Original post by Cleoleo)
The question was show the effect of excess alkali on the molecule.

I understand the -OH becomes O- becomes the phenol acts as an acid and the NaOH as a base but HO3S is also an acid, but I didn't realise this and thought they'd be no effect.

What indication is there that this acts as an acid like the -OH group ?

Thanks alot

Simply put, acidity is related to the stability of the conjugate base (the anion you get after deprotonation).

Stability of the anion is all about delocalising the negative charge produced. This is why COOH groups and phenol are acidic, as the negative charge is stabilised by delocalisation over several atoms. H2SO4 is also acidic because the sulphate anion is stable.

If you come across a compound and you're not sure if it will be acidic, think about how the negative charge might be delocalised (or localised on an electronegative element such as oxygen). The SO3H group can delocalise the negative charge over the three oxygens and the sulphur, so it's a stable anion.

[Cleoleo]

(Original post by illusionz)
Simply put, acidity is related to the stability of the conjugate base (the anion you get after deprotonation).

Stability of the anion is all about delocalising the negative charge produced. This is why COOH groups and phenol are acidic, as the negative charge is stabilised by delocalisation over several atoms. H2SO4 is also acidic because the sulphate anion is stable.

If you come across a compound and you're not sure if it will be acidic, think about how the negative charge might be delocalised (or localised on an electronegative element such as oxygen). The SO3H group can delocalise the negative charge over the three oxygens and the sulphur, so it's a stable anion.

Thanks, that was a really amazing explanation But sorry to annoy you but just wondered exactly how you knew it could delocalise the charge and how you knew it would be stable ?

[illusionz]

(Original post by Cleoleo)
Thanks, that was a really amazing explanation But sorry to annoy you but just wondered exactly how you knew it could delocalise the charge and how you knew it would be stable ?

Because it's a similar structure to a COOH. Replace the C with an S, and add another O.

It's also similar to sulphuric acid: