The intramolecular rotation of several C-O and C-C bonds of a set of aliphatic ethers were studied using quantum-chemical calculations at the RB3LYP 6-311++G(3df,3pd) level of theory. For molecules of di-npropyl (I), diisopropyl (II), methyl-n-propyl (III) and methyl isopropyl (IV) ether, the most stable conformations were found, geometric parameters and rotational constants were optimized, relative energies were estimated, and fundamental vibrations were simulated for each of them. The rotational (conformational) isomerism of these flexible aliphatic ethers with carbon and oxygen atoms in an sp(3) hybridized state are examined. Thermodynamic functions for di-n-propyl (I), diisopropyl (II), methyl-n-propyl (III) and methyl isopropyl (IV) ethers in the ideal gas state in the temperature range T = (50-1500 K) were calculated for the first time using molecular and spectral data. (C) 2019 Elsevier Ltd.