Liquid−Liquid Equilibria for Systems Containing 2-methoxyphenol or 2- ethoxyphenol and Selected Alkanes

Abstract

For several years ago, we have been interested on the investigation of intramolecular effects between the phenyl ring (C6H5-group) and a polar group, X, more or less directly attached to aromatic ring, as these effects are very different to those between the same groups when they belong to different molecules. For example, the upper critical solution temperature (UCST) of the phenol + decane mixtures is 336,50 K [1], while the excess molar enthalpy, 𝐻𝑚 𝐸 , of decan-1-ol + benzene system at equimolar composition and 298.15 K is 1050 J. mol-1, extrapolated value [2]. That is, intramolecular effects lead to enhanced interactions between like polar molecules, while intermolecular effects make usually more favourable in interactions between unlike molecules. For this purpose, we have studied, experimental and theoretically, intramolecular effects, also termed proximity effects, in mixtures containing aromatic amines [3-11] (anilines, 2-amino-1-methylbenzene, 1-phenylmethanamine, 2-ethoxy-benzenamine, 4-ethoxybenzenamine, 1H-pyrrole, quinoline or imizadoles); phenylmethanal, 1-phenylethanone, 4-phenyl-2-butanone, benzyl ethanoate [12-15], benzonitrile, phenylacetonitrile, 3-phenylpropionitrile [16], 2-phenoxyethanol or aromatic alkanols (phenol, phenylmethanol, 2-phenylethan-1-ol) [17-19]. As a continuation, we provide now liquid-liquid equilibria data for alkane systems involving 2methoxyphenol (guaiacol) or 2-ethoxyphenol. Alkoxyphenol molecules exhibit unique structural characteristics, wherein two distinct polar groups (-OH and -O-) are attached to the phenyl ring at different positions. It is anticipated that intramolecular interactions between these two groups play a significant role. In a previous study conducted by our research group, we investigated the phenoxyethanol + alkane systems [17]. However, this case presents a slight deviation, as the -O- and -OH groups are situated within the same linear chain that is connected to the phenyl ring. Phenol derivatives play a crucial role as intermediates in the synthesis of various specialty chemicals. Understanding the phase behaviour of these product mixtures is of utmost importance for the development of manufacturing processes. Alcoxyphenols exhibit diverse applications. For instance, 2-methoxyphenol serves as an expectorant and finds utility as an antioxidant and anti-skinning agent in the context of paints. It also serves as a precursor for flavourings such as eugenol and vanillin, and is employed as an intermediate in the chemical synthesis of active pharmaceuticals, flavouring agents, and perfumery products. Additionally, it acts as an indicator in chemical reactions that generate oxygen. In studies focused on phenolic compounds' ability to inhibit oral bacteria, 2-ethoxyphenol is employed. 2-ethoxyphenol is also investigated for its potential as a cyclooxygenase inhibitor for prostaglandins. Moreover, it serves as a reagent for the stereoselective preparation of (arylthiomethyl)morpholines, which are selective inhibitors of norepinephrine reuptake and dual inhibitors of serotonin/norepinephrine reuptake