[jean]

I am quite confuzed with the order of the good leaving group

I think the order is that: F->Cl->Br->I->TosO->MsO-

The best leaving group is that best stabilize the negative charge----the weakest bases---the anions derived from the strongest acids.


But why the order is reversed. I am really quite confuzed be this. Please help me?
 

[movies]

For one thing, check out the bond energies.

[Donaldson Tan]

shouldn't the order be reverse?

the less reactive the leaving group, the better leaving group it is. TsO- is definitely more stable than fluoride. TsO- is somewhat similar to sulphate(VI) anion.

[Winga]

Besides bond energy, you can also think of the stability of the negative charged ions as you said.

What do you think about the charge density of F- ion?


Better the leaving groups, weaker the bases.

As you said weak bases are come from strong acids, therefore, which one is a stronger acid, HF or HI? (think about the bond energies)

Then, which one is a weaker base, F- or I-?

[carl_pitt]

better living group is weaker base = conjucated strong acid it means : OTS>I>Br>Cl>F
you can also think about a F with negative charge.that is unstable couse it has small size and high negative charge but Iodin with negative charge is more stable cause charge/size relation is smaller.