Ricci Andreina, Pepi Federico, Cimino Paola, Troiani Anna, Garzoli Stefania, Salvitti Chiara, Di Rienzo Brunella, Barone Vincenzo
Department of Mathematics and Physics, Second University of Naples, Viale Lincoln,5, 81100, Caserta, Italy.
Department of Chemistry and Drug Technologies, 'Sapienza' University of Rome, P.le A. Moro 5, 00185, Rome, Italy.
J Mass Spectrom. 2016 Dec;51(12):1146-1151. doi: 10.1002/jms.3848.
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, [C H O ]H , were generated by electrospray ionization of a 10 M H O/CH OH (1 : 1) AA solution. In order to structurally characterize the gaseous [C H O ]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 and protonation entropy ΔS 108.9 ± 2 J mol K , a gas-phase basicity value of AA of 842.5 ± 12 kJ mol at 298 K was obtained, which is in agreement with the value issuing from quantum mechanical computations. Copyright © 2016 John Wiley & Sons, Ltd.
为了研究抗坏血酸（AA）酸催化降解为呋喃的气相机制，我们在B3LYP/6 - 31 + G(d,p)理论水平上进行了质谱分析（ESI/TQ/MS）和理论研究。气态反应物物种，即质子化的AA，[C₆H₈O₆]H⁺，是通过对10⁻³ M H₂O/CH₃OH（1∶1）的AA溶液进行电喷雾电离产生的。为了从结构上表征气态[C₆H₈O₆]H⁺离子反应物，我们通过扩展的库克斯动力学方法以及在B3LYP/6 - 31 + G(d,p)理论水平上的计算方法，估算了AA的质子亲和能和气相碱度。正如预期的那样，计算结果确定AA的羰基氧原子（O2）为优先质子化位点。根据875.0 ± 12 kJ mol⁻¹的实验质子亲和能和108.9 ± 2 J mol⁻¹ K⁻¹的质子化熵，在298 K时得到AA的气相碱度值为842.5 ± 12 kJ mol⁻¹，这与量子力学计算得出的值一致。版权所有© 2016约翰威立父子有限公司。
