Synthesis and properties of symmetric glycerol-derived (E/Z)-1,3-diether-2-alkenes

Abstract

The synthesis of new and potentially “green” solvents and other small molecules/intermediates from glycerol and associated derivatives is promising for expanding glycerol valorization. Previously, we showed that eliminating H-bonding reduces solvent–solvent interactions and increases CO₂ solubility in 1,3-diether-2-ketones compared to 1,3-diether-2-alcohols based on glycerol skeletons. Further exploration of glycerol-derived 1,3-diether-2-propanol compounds into corresponding 1,3-diether-2-alkenes can yield valuable insights into structure–property relationships as well as new chemical intermediates. In the current work five symmetric glycerol-derived (E/Z)-1,3-diether-2-alkenes were synthesized: 1,3-dimethoxyprop-1-ene ([M, A, M]), 1,3-diethoxyprop-1-ene ([E, A, E]), 2,5,9,12-tetraoxatridec-6-ene ([ME, A, ME]), 1,3-bis(2,2,2-trifluoromethoxy)prop-1-ene ([F, A, F]), and prop-1-ene-1,3-diylbis(oxy)bis(methylene)dibenzene ([Bn, A, Bn]), using a three-step strategy starting from epichlorohydrin. All compounds were purified using thorough distillation and drying methods. The E : Z ratio in all products was close to 1 : 1. Thermophysical properties of the synthesized (E/Z)-1,3-diether-2-alkenes (e.g., density, refractive index, viscosity) were measured over the range of T = 293.15–333.15 or 343.15 K. CO₂ absorption capacities (Henry's constants) of [F, A, F] were measured at T = 303.15, 318.15, 333.15, and 348.15 K and pressures in the range of P = 2–10 atm. Density, viscosity, vapor pressure, enthalpy of vaporization, and dipole moment were also calculated for each compound. Additionally, it was demonstrated that the CC bond remains accessible for further reactions and can undergo bromination and thus may also have applications as intermediates for more complex molecules that are based on glycerol skeletons.

Keywords: Glycerol; Green solvents; CO₂ absorption; Symmetric alkenes; Platform molecules.