Stability of gem diols lies on the following factors:

(a) Steric hindrance by +I group around α-carbon decreases the stability of gem diols. +I group decreases stability of gem diol and therefore decreases extent of hydration.

(b) Stability of gem diols mainly relies on the existence of -I group on α-carbon. More is the -I power of the group much more will be stability of gem diols.

(c) Intramolecular hydrogen bonding raises stability of gem diols. -I set depicts on carbon having gem diol group increases strength of hydrogen bond.

Much more is the power of hydrogen bond more will be the stability of gem diol.