How to compare reactivity of different chemical groups attached to the same substrate

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Chuckj
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There are several substanecs different only in a chemical group linked to the same opsition for all those substances. how can i know which one reacts fastest ?

ie , OH-R, ON_2-R, O_3P-R, O_4S-R...

Thanks
 
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Chuckj said:
There are several substanecs different only in a chemical group linked to the same opsition for all those substances. how can i know which one reacts fastest ?

OH-R, ON_2-R, O_3P-R, O_4S-R...

It depends what you are trying to do.

If it's aromatic substitution, more negative stuff connected to the aromatic makes a faster reaction. OH on a benzene ring is a very strong activating group, so phenol will react quickly. Same deal with aniline, NH2 is a strong activating group. NO2 on a benzene ring is a strong deactivating group (the oxygens make the nitrogen positive), so nitrobenzene is a slouch when it comes to reactions.

If it's nucleophilic substitution, the speed is determined by the stability of the leaving group. OH is a horrible leaving group, so that is a slow reaction. SO4H is an excellent leaving group, so that will leave quickly. Water is an even better leaving group, so using acid around oxygens makes stuff happen faster (true for both organic and inorganic).
 
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Thank you very much,
But what if I have substances like

OH-R-COOH
O2N-R-COOH
O4P-R-COOH
...
how can i explain then ?
 
which reaction are you referring to?