Hey this is my doubt .... Is hydroxyl group(-OH) electron withdrawing or electron releasing group??? I have heard that it is EWG with aliphatic molecules and EDG with aromatic molecules is it true ??? Kindly reply and im sure to approve !!!

actually OH group is electron releasing as well as electron withdrawing group ...

-I effect (inductive effect) => in accordance with this effect OH group will show -I (electron withdrawing) effect due to presense  of an electronegative Oxygen atom ...

+R effect (resonance effect) => in accordance with this effect OH group will show is +R(electron releasing ) effect due to presence of lone pair of electrons on oxygen ...

when ever their is comparision in bw resonance & inductive or hyperconjugation then more priority is given to

resonance effect ....

example ->   CH₃CH₂OH     -       -I effect  ,   no resonance     -  OH group is electron withdrawing

                   CH₂=CH-OH    -       -I effect ,    +R effect            - OH group electron releasing        (possiblity of resonance)

                     phenol          -       -I effect ,   +R effect            -  OH group is electron releasing    (possiblity of resonance)

this is not always true that if OH is attached to aliphatic molecules then it is EWG , if there is

possiblity of resonance then it will become EDG ...

if u still have doubt then ask