Volume properties of tetramethylenediethylenetetramine (pharmaceutical teotropine) in aqueous solutions between 278.15 and 318.15 K

• Standard molar volumes of teotropine (tetramethylenediethylenetetramine – TMDETA) in water were determined densimetrically. • Density measurements were performed at temperatures from 278.15 K to 318.15 K (with a step of 10 K) at ambient pressure. • Like the related aminal solute urotropine (hexamethylenetetramine – HMTA), TMDETA has a structure-making effect in water. • Structure packing of the hydration complex formed becomes denser and thermally more stable when going from HMTA to TMDETA. • Structure-forming effect (due to hydrophobic effects and H-bonding) is greater in aqueous TMDETA as a bulkier aminal solute. The densities of aqueous solutions of tetramethylenediethylenetetramine (the teotropine pharmaceutical) with the solute molality from (0.01 to 0.12) mol·(kg water) −1 were measured at T = (278.15, 288.15, 298.15, 308.15, and 318.15) K and p = 0.1 MPa. The uncertainty in density measured using the Anton Paar DMA 5000 M densimeter (equipped with an oscillating U-tube) was estimated to be 0.03 kg m −3 or lower. The standard (apparent at infinite dilution) molar volumes and expansibilities of teotropine were computed. Based on the analysis of contributions to the standard molar volume in terms of the Scaled Particle Theory was confirmed that a bulkier molecule of teotropine interacts with water stronger than it does a molecule of urotropine or hexamethylenetetramine – the related aminal (cage-like) compound.