Thermodynamics of Transfer of Some Alkyl Acetates from Water to Water–Ethanol Mixtures

Summary. The solubility of methyl acetate (MeOAc), ethyl acetate (EtOAc), 1-propyl acetate(1-PrOAc), 1-butyl acetate (1-BuOAc), 2-methyl-1-propyl acetate ( iso -BuOAc), 2-butyl acetate ( sec -BuOAc), 2-methyl-2-propyl acetate ( tert -BuOAc), 1-pentyl acetate (1- Pe OAc), and 1-hexyl acetate(1- He OAc) in 2.5, 5.0, 7.5, and 10.0 weight per cent of ethanol in water were determined at 298.2 K. The solubility of the same compounds, except for tert -BuOAc, 1- Pe OAc, and 1- He OAc, was determined as a function of temperature at 10.0 weight per cent of ethanol in water. From the solubility measurements the standard Gibbs energy (Δ G t 0 ), enthalpy (Δ H t 0 ), and entropy (Δ S t 0 ) of transfer were determined. The calculated thermodynamic functions show that the predominant factors in the transfer of alkyl acetate molecules are the transfer of the cavity and the hydrophobic interaction of the non-polar alkyl chain. Scaled particle theory calculations were used to determine the thermodynamics of cavity transfer, which were combined with the experimental total transfer quantities to obtain the corresponding interaction transfer quantities. It was found that the Gibbs energy of interaction for the transfer is negative, whereas the enthalpy and entropy of interaction for the transfer are positive; almost complete compensation of enthalpy and entropy components occurs.