Characterization of two lactones in liquid phase: an experimental and computational approach.

In this work, an experimental and computational study on the properties and molecular-level liquid structure of gamma-butyrolactone and gamma-valerolactone is reported. These fluids are selected because of their possible use as alternative green solvents considering their favorable environmental and toxicological profiles. The experimental study was carried out measuring a selected collection of relevant thermophysical properties, at ambient pressure as a function of temperature, together with a detailed spectroscopic study. The reported set of experimental thermophysical properties is valuable for process design purposes and because of their relationships with microscopic fluids' structure. Spectroscopic studies were carried out using attenuated total reflection infrared spectroscopy (ATR-FTIR), solvatochromic studies and microwave dielectric relaxation spectroscopy (DRS) measurements; all the spectroscopic studies were performed as a function of temperature. Moreover, density functional theory (DFT) and classical molecular dynamics simulations (MD) were used to obtain a detailed picture of the intermolecular interactions within the fluid, at short and long ranges, and of other relevant features leading to the liquid structure of the studied fluids. The whole study points to a fluids' picture in which, in spite of the absence of specific interactions such as hydrogen bonding, a remarkable ordering appears rising from the dipolar interactions and from the shapes of the involved molecules.