Ranking of Leaving Groups

[emminent]

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Order of best to worst LG:

F
OH
tosylate
CH3O
H

I know that toyslate group is the best but what about the others?
Would it be: tosylate>CH3O>OH>F>H?

 

[discensdentibus]

tosyl> F> OH/OCH3> H

Fluoride a poor, relative to the other halogens. Someone may wanna double check against a textbook, but I am pretty sure it still trumps an oxygen because it can better bear a negative charge.

 

[jwan14]

I think F is higher than OH. It's more stable when it leaves. I'm confused about that CH3O molecule. Is it a negatively charged O? I think it would be Tosylate>CH3O(resonance)>F>OH>H

 

[emminent]

It's from Destroyer. No charges are listed. I put it exactly as is except for the toyslate group which is listed by the molecular shape not name.

 

[discensdentibus]

A methoxide's electrons are localized. You have to consider acid catalyzed carboxylic acid derivate chemistry in one sense as well as alcohol chemistry. Very very rarely do you see a hydroxy leave without being protonated first. Same goes for methoxide.

 

[emminent]

I thought F was a bad LG. Wasn't it I>Br>Cl>F?

 

[discensdentibus]

Think about it this way: (ranked by decreasing reactivity) Acyl halides (which does include F) > anhydrides> rcooh

F is bad, RELATIVE to other halides. Look in your textbook. F doesn't need to be protonated to become a good leaving group. It can participate in elimination rxns, for instance, though it does go through a carbanion-like transition state.