Computational work is presented addressing the viability and efficacy of carbonic acid (H2CO3) as a protonation agent. The formation and separation for a carbonic acid-base pair, for two different bases (methylamine and aniline), are followed via Car-Parrinello molecular dynamics (CPMD) simulations. Protonation mechanisms for the methylamine bases are compared for a direct contact acid-base H-bonded complex and when one to two water molecules bridge the acid-base pair. The direct contact protonation of the weaker base aniline is compared to that for methylamine to further evaluate the acidity of carbonic acid. CPMD simulations are complemented with an evaluation of the proton transfer free energy barrier for each mechanism, including explicit evaluation of the proton's quantum zero-point motion. The projected PT rate constants are compared and the efficacy of carbonic acid as a mobile buffer in vivo is discussed.This collaboration was supported by an NIH grant (R01GM101160).

Computational studies of base protonation by carbonic acid in an aqueous solution

248th National Meeting (2014)

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