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Priyanshu kumar Best Answer
para fluoro phenol is least acidic
In case of p-fluorophenol +R-effect and -Ieffect of Fluorine almost balance each other, hence almost no difference in acidity between p-fluorophenol and phenol.
Here fluorine act as +R effect?
while other halogens act as -I effect??
halogens show both -I effect and +,R effect but in halogens -I effects dominates
So all halo phenols are more acidic than phenol
but in para fluorophenol these two opposite effects counterbalances
see pka values
Sir what about if all halogens are at ortho and meta position
In meta position only inductive effects acts no mesomeric effect
so for meta position -I effect of F>Cl>Br>I
got it shristy??
N for ortho effect ?? same as para ??
here new factor hydrogen bonding works at ortho position
In o-fluorophenol fluorine is highly electronegetive, forming H- bond with the H atom of OH group. So the acidic nature of this OH is lowest.
And the rest order follow -I effect at ortho position..means ochloro phenol>o bromo phenol>o iodo phenol>o fluoro phenol
now got it shristy??
ok sir thanku
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