“…This can be explained by the increase in partial positive charge on the sulfur in sulfinic acid, which converts the sulfur atom into a harder electrophile making it less prone to reaction with soft nucleophiles, such as thiols. With a p K a of 2 , sulfinic acid is deprotonated at physiologic pH and can exist in two resonance forms (Chart ) . Sulfinic acids function as nucleophiles (Chart ), reacting largely from sulfur to undergo alkylation ( 27 ), as well as nucleophilic addition to activated alkenes ( 28 ), aldehydes ( 29 ), lactones ( 30 ), α,β-unsaturated compounds ( 31 ), and diazonium salts ( 32 ) to give the corresponding sulfones. , The preceding reactions are established for sulfinic acids under synthetic organic conditions, but it is not established whether all of these reactions would take place with protein sulfinic acids.…”