Between fluorine and chlorine which has greater +M effect when attached to vinyl group.
The confusion is, thiophene has almost twice the resonance energy of furan which encourage to think chlorine has better +M.
Now when we compare acidic strength of these two lewis acids BF3 and BCl3( latter on is stronger) it encourage to think fluorine has better +M effect than chlorine.
Kindly help me out..
No one in this group are enough concern 'bout any question. They are all involved in making their carrer hahaha...