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采用傅里叶变换红外光谱法 (FTIR)和二维相关分析 (2DCorrelationAnalysis)技术研究了固态抗坏血酸在 2 0℃～ 1 60℃的升温氧化过程。结果表明 :抗坏血酸随着温度升高的红外光谱的特征峰在一维图上变化不明显。借助于二维相关分析 ,不仅提高了谱图的分辨率 ,将一维红外谱图上 1 674cm- 1 处的单峰分解为两个自相关峰 ,显示了抗坏血酸的互变异构体中酮式结构的CO基团和醇式结构的CC基团的振动 ;还揭示了分子内各官能团之间的相互作用 ,反映了在升温氧化过程中这些基团之间的协同关系和变化的先后顺序。抗坏血酸分子中CO、CC和COC基团发生了相互作用 ,其变化的顺序是CC先于COC发生偶极矩的变化 ,最后是CO发生变化 ,此现象与抗坏血酸的氧化反应机理相一致。总之 ,二维相关红外分析可以作为研究抗坏血酸升温氧化过程中结构动态变化的一种新方法 ,也为抗坏血酸在氧化过程中的机理研究提供了一个重要的理论依据。
The oxidation process of solid ascorbic acid at 20 ℃ ~ 1 60 ℃ was studied by Fourier transform infrared spectroscopy (FTIR) and two-dimensional correlation analysis (2DCorrelationAnalysis). The results showed that the characteristic peaks of the infrared spectra of ascorbic acid did not change obviously in the one-dimensional diagram as the temperature increased. With the help of two-dimensional correlation analysis, not only the resolution of the spectrum is improved, the unimodal peak at 1 674cm-1 in the one-dimensional infrared spectrum is decomposed into two autocorrelation peaks, which shows that the ketones in tautomers of ascorbic acid The CO group of the structure and the CC group of the alcoholic structure. It also reveals the interaction among the functional groups in the molecule, and reflects the order of the synergies and changes between these groups in the process of temperature increase and oxidation . Ascorbic acid molecules CO, CC and COC groups interact, the order of its change is CC before dipole moment COC changes, and finally CO changes, this phenomenon is consistent with the oxidation reaction mechanism of ascorbic acid. In conclusion, two-dimensional IR analysis can be used as a new method to study the structural dynamics during the oxidation of ascorbic acid and provide an important theoretical basis for the study of the mechanism of oxidation of ascorbic acid.