188819-30-9Relevant articles and documents
Kinetics of reversible carbon deprotonation of 2-nitroethanol and 2-nitro-1,3-propanediol by hydroxide ion, water, amines, and carboxylate ions. A normal br?nsted α despite an imbalanced transition state
Bernasconi, Claude F.,Panda, Markandeswar,Stronach, Michael W.
, p. 9206 - 9212 (2007/10/03)
Rates of reversible carbon deprotonation of 2-nitroethanol (2) and 2-nitro-1,3-propanediol (3) by hydroxide ion, water, amines, and carboxylate ions and pKa values for the ionization at carbon (pKaCH) and oxygen (pKaOH) and ionization of the aci-forms (pKaNOH) were determined in aqueous solution at 25 °C. The pKaCH values for 2 and 3 are 8.60 and 7.68, respectively, as compared to 10.22 for CH3NO2. The acidifying effect of the CH2OH groups is attributed to a combination of inductive electron withdrawal and hyperconjugative stabilization of the respective nitronate ions, possibly coupled with intramolecular hydrogen bonding stabilization of this ion. The higher acidity of 2-nitroethanol compared to nitromethane is reflected in higher rates of proton transfer from 2-nitroethanol, implying a "normal" Br?nsted α between 0 and 1. This contrasts with the negative α value based on the reaction of OH- with nitromethane, nitroethane, and 2-nitropropane (Kresge, A. J. Can. J. Chem. 1974, 52, 1897). Reasons why a normal α value is observed in the current system are discussed.