Vitamin C: an experimental and theoretical study on the gas-phase structure and ion energetics of protonated ascorbic acid

作者：Ricci Andreina^*; Pepi Federico; Cimino Paola; Troiani Anna; Garzoli Stefania; Salvitti Chiara; Di Rienzo Brunella; Barone Vincenzo

来源：Journal of Mass Spectrometry, 2016, 51(12): 1146-1151.

DOI：10.1002/jms.3848

• protonated ascorbic acid
• mass spectrometry
• kinetic method
• gas-phase basicity of ascorbic acid
• quantum mechanical calculation

In order to investigate the gas-phase mechanisms of the acid catalyzed degradation of ascorbic acid (AA) to furan, we undertook a mass spectrometric (ESI/TQ/MS) and theoretical investigation at the B3LYP/6-31+G(d,p) level of theory. The gaseous reactant species, the protonated AA, [C6H8O6]H+, were generated by electrospray ionization of a 10(-3) M H2O/CH3OH (1 : 1) AA solution. In order to structurally characterize the gaseous [C6H8O6]H+ ionic reactants, we estimated the proton affinity and the gas-phase basicity of AA by the extended Cooks's kinetic method and by computational methods at the B3LYP/6-31+ G(d, p) level of theory. As expected, computational results identify the carbonyl oxygen atom (O2) of AA as the preferred protonation site. From the experimental proton affinity of 875.0 +/- 12 kJ mol(-1) and protonation entropy Delta S-p 108.9 +/- 2 J mol(-1) K-1, a gas-phase basicity value of AA of 842.5 +/- 12 kJ mol(-1) at 298 K was obtained, which is in agreement with the value issuing from quantum mechanical computations.

• 出版日期2016-12