Infrared study and thermodynamics of hydrogen bonding in tri- and tetra-methylene glycol monomethyl ethers

Abstract

Tri- and tetra-methylene glycol monomethyl ethers in very dilute carbon tetrachloride solutions (C < 0.025 mol dm^–3) exhibit free OH bands at ∼ 3630 cm^–1 and intramolecularly H-bonded OH bands at ∼3540 and 3450 cm^–1 respectively. The thermodynamic quantities involved in the M_I⇌ M_F equilibria are: ΔH°= 15 kJ mol^–1, ΔS°= 52 J K^–1 mol^–1 and K(at 298 K)= 1.4 for trimethylene glycol monomethyl ether. For tetramethylene glycol monomethyl ether ΔH°= 18 kJ mol^–1, ΔS°= 68 J K^–1 mol^–1 and K(at 298 K)= 2.2. In the concentration range 0.02–0.20 mol dm^–3, the self-associated species are found to form a mixture of open + closed dimers and trimers while above 0.2 mol dm^–3 higher associated species are present. The self-association behaviour of these compounds is thus similar to that of simple alcohols.