if there is an acyl chloride (COCL)
can other halogen be a nucleophile and attack the carbonyl carbon and kick the chloride out?
weaker base tends to be 'kicked' out from the tetrahedral intermediate.
the weaker base is the more electronegative base
but literally among F CL Br I halogens
F is the most electronegative but the strongest conjugate base....
confusing...T_T?