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

Excess molar volumes V-m(E) at 318.15 K and atmospheric pressure for 1-prop anol or 1-hexanol + dibutyl ether, 1-propanol or 1-hexanol + 2,5-dioxahexan e, 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 vib rating-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 ric h in the alkanol, increasing their asymmetry with the number of oxygen grou ps 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 dV(m)(E)/dT is discussed. Systems with 1-propanol are character ized by dV(m)(E)/dT > 4 which may be due to the more self-associated charac ter of the alcohol. In solutions with 1-hexanol, the sign of dV(m)(E)/dT de pends on the ether considered, i.e. on the balance between the interactiona l and structural contributions. So, if the latter are more important, then dV(m)(E)/dT > 0. Results remark the differences between systems containing n-alkanols and mo noethers or polyethers. (C) 2000 Elsevier Science B.V. All rights reserved.