Borate esters B(OR)3 and boronate esters RB(OR)2 undergo ion-molecule reactions to yield both addition products (by an implied radiative emission mechanism), ligand exchange, and proton transfer products, in both positive and negative ion modes. Although an acidity for CH3B(OR)2 could not be determined, HOB(OR)2 has an acidity between acetaldehyde and nitromethane. In light of the negligible polar electron acceptor properties of the -B(OR)2 group, that functionality must therefore be one of the best resonance electron acceptor groups known, almost half again as effective as the nitro group.