The polarity of oxygen also makes the alpha hydrogens of carbonyl compounds "much" more acidic (roughly 1030 times more acidic) than typical sp3 C-H bonds, such as those in methane. For example, the pKa values of acetaldehyde and acetone are 16.7 and 19 respectively, while the pKa value of methane is extrapolated to be approximately 50. This is because a carbonyl is in tautomeric resonance with an enol. The deprotonation of the enol with a strong base produces an enolate, which is a powerful nucleophile and can alkylate electrophiles such as other carbonyls.