Organic chemistry protic solvent question sn1?

OH- is a better nucleophile because it has much higher charge delocalization. More negative charged substances are generally better nucleophiles. Water is also the weaker base - which is the equivalent of saying that it is a more stable base. OH is also more electronegative than water is due to the shape of the molecule. OH- has a much greater dipole moment (the electron cloud greatly favors oxygen) whereas bent H20 molecule has a much less pronounced dipole.