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首页> 外文期刊>Journal of mass spectrometry: JMS >Vitamin C: an experimental and theoretical study on the gas-phase structure and ion energetics of protonated ascorbic acid
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Vitamin C: an experimental and theoretical study on the gas-phase structure and ion energetics of protonated ascorbic acid

机译：维生素C：质子抗坏血酸气相结构和离子能量学的实验与理论研究

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摘要

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. Copyright (C) 2016 John Wiley & Sons, Ltd.
机译：为了研究抗坏血酸（AA）对呋喃的酸催化降解的气相机制，我们在B3LYP / 6-31 + G处进行了质谱（ESI / TQ / MS）和理论研究（D， p）理论水平。通过电喷雾电离为10（-3）M H 2 O / CH 3 OH（1：1）AA溶液，产生气态反应物物种，质子化AA，[C6H806] H +。为了在结构[C6H8O6] H +离子反应物的结构上表征，我们通过延长的厨师的动力学方法和B3LYP / 6-31 + G的计算方法估计了AA的质子亲和力和气相碱度（D，P ）理论水平。正如预期的那样，计算结果鉴定AA的羰基氧原子（O2）作为优选的质子化位点。从875.0 +/- 12 kJ摩尔（-1）和质子化熵的实验性质子亲和力来自108.9 +/- 2 J mol（-1）K-1，AA的气相碱性值为842.5 +/-获得了12 kJ摩尔（-1）在298 k处获得，这与从量子机械计算发出的值一致。版权所有（c）2016 John Wiley＆Sons，Ltd。

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