Temperature dependence of excess properties in alcohols+ethers mixtures.: I. Excess molar volumes of 1-propanol or 1-hexanol+ethers at 318.15 K

Excess molar volumes V m E at 318.15 K and atmospheric pressure for 1-propanol or 1-hexanol+dibutyl ether, 1-propanol or 1-hexanol+2,5-dioxahexane, 1-propanol or 1-hexanol+2,5,8-trioxanonane, 1-propanol or 1-hexanol+3,6,9-trioxaundecane and 1-propanol or 1-hexanol+5,8,11-trioxapentadecane, have been obtained from densities measured with an Anton-Paar DMA 602 vibrating-tube densimeter. All the excess volumes are negative over the whole mole fraction range, except for the systems 1-propanol+2,5,8-trioxanonane, which is S-shaped, and for 1-hexanol+2,5-dioxahexane or 1-hexanol+2,5,8-trioxanonane which are positive over the whole mole fraction range. For the systems with 1-propanol the V m E curves are shifted to the region rich in the alkanol, increasing their asymmetry with the number of oxygen groups in the ether. For 1-hexanol systems the V m E curves are symmetrical. This behaviour can be attributed to free volume effects. The sign of d V m E/d T is discussed. Systems with 1-propanol are characterized by d V m E/d T>0, which may be due to the more self-associated character of the alcohol. In solutions with 1-hexanol, the sign of d V m E/d T depends on the ether considered, i.e. on the balance between the interactional and structural contributions. So, if the latter are more important, then d V m E/d T>0. Results remark the differences between systems containing n-alkanols and monoethers or polyethers.