A detail study of the microstructure of methyl benzoate/methanol mixture proved by IR spectra, excess infrared wavenumber, and physicochemical properties
A detail study of the microstructure of methyl benzoate/methanol mixture proved by IR spectra, excess infrared wavenumber, and physicochemical properties
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DOI：
10.1016/j.molliq.2020.112521
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发表时间：
2020-03
影响因子：
6
通讯作者：
Xiao Feng;Tingting Chen;Yuqiao Yin;Yingjie Xu
中科院分区：
文献类型：
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作者：
Xiao Feng;Tingting Chen;Yuqiao Yin;Yingjie Xu
通过对比苯甲酸甲酯(MB)/甲醇- 4和MB/正己烷混合物的红外光谱，发现前者体系中MB的酯基（o双键c单键do）的红外波数（υ￣）随着MB摩尔分数（x 1）的增加呈指数下降，而后者体系中MB的红外波数（υ￣）呈线性下降，表明h键相互作用在MB/甲醇- 4混合物的微观结构中起重要作用。因此，为了探索MB/甲醇混合物的微观结构和表征氢键相互作用的强度，提出了基团（υ ~基团E）的过量红外波数，表明甲醇- D - 4的υ ~ O−D - E呈现S形，最小值为x 1≈0.4，最大值为x 1≈0.8。此外,υ的绝对值˜O−D E(|υ˜O−D E |)前者大于后者,表明H-bonding之间交互methanol-d 4分子比,methanol-d 4 MB。虽然υ˜C = O E和υ˜C−O E MB显示负偏差的最小值在x 1≈0.4,和|υ˜C = O E |大于|υ˜C−O E |,表明Cdouble bondO直接参与H-bonding互动Osingle bondD,通过电子共轭效应导致υ ~ C−O E的变化。为了证实红外光谱得到的微观结构，测量了MB/甲醇混合物的密度、声速和粘度，并计算了过量性能。结果表明：过量摩尔体积和等熵压缩偏差均呈负偏差，最小值在x1≈0.4处，这与υ ~ O−D E、υ ~ C= O E和υ ~ C−O E的最小值对应的x 1有很好的一致性；黏度偏差表现为负偏差，最小值在x1≈0.8处，这与对应于υ ~ O−D E最大值的x1有很好的一致性。
By a comparative study of the concentration-dependent IR spectra of methyl benzoate (MB)/methanol-d 4 and MB/n-hexane mixtures, it is found that the infrared wavenumber (υ˜) of ester group (Odouble bondCsingle bondO) of MB in the former system decreased exponentially with the increase of mole fraction of MB (x 1), while that of the latter system decreased linearly, suggesting that H-bonding interaction plays an important role in the microstructure of MB/methanol-d 4 mixture. Therefore, to explore the microstructure and characterize the strength of H-bonding interaction of MB/methanol mixture, the excess infrared wavenumber of a group (υ˜ group E) is proposed, showing that υ˜ O− D E of methanol-d 4 presents an S shape with a minimum value at x 1≈ 0.4 and a maximum value at x 1≈ 0.8, respectively. Furthermore, the absolute value of υ˜ O− D E (| υ˜ O− D E|) of the former is greater than that of the latter, suggesting that H-bonding interaction in methanol-d 4 molecules is stronger than that between methanol-d 4 and MB. While both υ˜ C= O E and υ˜ C− O E of MB show a negative deviation with minimum values at x 1≈ 0.4, and| υ˜ C= O E| is larger than| υ˜ C− O E|, indicating that Cdouble bondO is directly involved in H-bonding interaction with Osingle bondD, resulting in the change of υ˜ C− O E through the electronic conjugation effect. To confirm the microstructure obtained from IR spectra, densities, speeds of sound, and viscosities of MB/methanol mixture are measured and excess properties are calculated. The results show that both excess molar volumes and isentropic compressibility deviations have a negative deviation with a minimum value at x 1≈ 0.4, which is good consistent with x 1 corresponding to the minimum value of υ˜ O− D E, υ˜ C= O E, and υ˜ C− O E, respectively. Moreover, viscosity deviations exhibit a negative deviation with a minimum value at x 1≈ 0.8, which is good consistent with x 1 corresponding to the maximum value of υ˜ O− D E.