A promising hydrotropic effect of Tetra n-octyl ammonium bromide (TOAB) for thermodynamic investigation of surface tension, conductivity of indole in water

Abstract

Abstract Hydrotropes are a class of compounds that improve aqueous solubility of certain organic compounds. The aqueous solubility arising from interfacial incompatibility has been a critical industrial concern, limiting various applications. Among many such hydrotropes, the purpose of this work is to study the effect of n-octyl tetra ammonium bromide (TOAB) over the organic-inorganic incompatibility of an indole water system experimentally through conductometry and stalagmometry, for the first time. The study focussed on conductometry to determine minimum hydrotrope concentration (MHC) through specific conductivity at different temperatures. The MHC is essential in ensuring the spontaneous self-assembly of organic molecules (such as indole) in water systems. In addition to this, MHC was also determined using stalagmometry at room temperature to analyse the hydrotropic effect of TOAB. Consequently, the Hydrotropy-assisted cooperative solubilization of indole in water was investigated by specific conductivity (7.64 µs/cm), surface tension (40.29 mN/m) and Gibb’s free energy at the minimum hydrotrope concentration (MHC∼ 0.95 mM) at room temperature. In conclusion, the experimental observation over the MHC is in good agreement with thermodynamic studies, suggesting the promising nature of TOAB in improving the aqueous solubility of Indole in water. GRAPHICAL ABSTRACT