If the lone pair donating tendency on oxygen is reduced, nucleophilicity reduced. This is because the electron density of larger atoms is more readily distorted since the electrons are further from the nucleus. H2O= Neutral molecule
CH3SO3⊖=CH3
O
||
S
||
O
−O−=Charged ion
CH3COO⊖=CH3−
C
||
O
−O−=Charged ion
⊖
O
H=Charged ion Thus, the increasing order of nucleophilicity is: H2O<CH3SO3⊖<CH3COO⊖<OH