STUDY OF THE STEAM DISTILLATION OF PHENOLIC-COMPOUNDS USING ULTRAVIOLET SPECTROMETRY
STUDY OF THE STEAM DISTILLATION OF PHENOLIC-COMPOUNDS USING ULTRAVIOLET SPECTROMETRY
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DOI：
10.1021/ac00294a034
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发表时间：
1986-03-01
影响因子：
7.4
通讯作者：
KELIHER, PN
中科院分区：
文献类型：
--
作者：
NORWITZ, G;NATARO, N;KELIHER, PN
结果与讨论酚类化合物的紫外光谱。在紫外光谱上运行的溶液应该是酸性的，以确保，在可能的情况下，酚化合物是烯醇形式而不是阴离子形式。酸度并不重要。对于苯酚，在0.1- 25ml / 100ml盐酸浓度为1n的范围内得到了相同的曲线。建议每100ml盐酸浓度为2毫升。酚类化合物的紫外光谱通常在210-220 nm附近有一个非常大的峰，在更高的波长处有一个较小的峰。考虑到较大的峰过于敏感，无法研究蒸馏过程，因此选择了波长较高的峰。对于每100毫升含有4毫克酚类化合物的溶液，该峰的吸光度通常约为0.4-1.2。然而，对单、二、三硝基苯酚的灵敏度要高得多，并且将这些化合物稀释至250毫升（在加入5毫升1 N盐酸后）。蒸馏过程的研究。如果溶液的pH值小于4，则蒸馏所用的酸度并不重要。加入2滴硫酸（1 ~ 9）后，溶液pH约为2.0。大部分酚类化合物是在蒸馏的最初几分钟里析出的。未蒸馏样品中该峰的最大吸收波长（Xmax）、该峰的毫摩尔吸收率（me）以及蒸馏样品中酚类化合物的回收率如表1所示。除氨基酚类和对苯二酚类外，所有样品的馏出物和残液中酚类化合物的总量都合理地接近100%，有
RESULTS AND DISCUSSION Ultraviolet Spectra of Phenolic Compounds. The so-lutions on which the ultraviolet spectra are run should be acidic in order to ensure, where possible, that the phenolic compound is in the enolic form and not the anionic form. The acidity is not critical. For phenol, the same curves were ob-tained over the range 0.1-25 mL of 1 N hydrochloric acid per 100 mL. Two milliliters of 1 N hydrochloric acid per 100 mL is recommended. The ultraviolet spectra of phenolic com-pounds usually show a very large peak in the vicinity of about 210-220 nm and a smaller peak (or peaks) at a higher wave-length. The large peak was deemed too sensitive tostudy the distillation process, so the peak at the higher wavelength was chosen. This peak ordinarily gave an absorbance of about 0.4-1.2 for a solution containing 4 mg of the phenolic com-pound per 100 mL. However, the sensitivities for the mono-, di-, and trinitrophenols were much greater and for these compounds the dilution was made to 250 mL (after adding 5 mL of 1 N hydrochloricacid). Study of the Distillation Process. The acidity for the distillation is not critical, providing that the pH of the solution is less than about 4. The pH of the solution after adding the 2 drops of sulfuric acid (1 to 9) was about 2.0. Most of the phenolic compound comes over during the first few minutes of the distillation.The wavelength of maximum absorption (Xmax) of the peak in the undistilled sample, the millimolar absorptivity (me) of this peak, and recovery of the phenolic compound in the distilled sample are shown in Table I. For all the samples except the aminophenols and hydroquinone, the total of the phenolic compound in the distillate and residual solution was reasonably close to 100% and there