The static relative permittivity and density of 1-heptanol, 3-heptanol, 3-methyl-2-hexanol, 2-methyl-2-hexanol have been measured as a function of pressure up to 3.5 kbar and from -30 degrees to 100 degrees C. The static relative permittivity has been observed to be a sensitive function of pressure, temperature and the isomeric structure of the alcohol. The Kirkwood dipole correlation factor g has been calculated from the experimental results and its pressure and temperature dependence has been discussed in terms of isomeric structure. At a temperature of -30 degrees and a pressure of 3 kbar, an increase in g by a factor of 8 above the ambient pressure value for 2-methyl-2-hexanol compares with a similar increase by a factor of 1.4 for 3-methyl-2-hexanol. The results are compared with other studies of the effects of pressure on alkanols and their isomers. Reference is made to the possible importance of the existence of different optically active isomers in the samples studied.
The complex relative permittivity of 1-heptanol, 3-heptanol, 3-methyl-2-hexanol and 2-methyl-2-hexanol has been measured from -30 degrees C to 20 degrees C at pressures up to 350 MPa in the range of frequencies between 50 Hz and 6 MHz. The dispersion in 1-heptanol and 3-heptanol is well characterised by the Debye equation, whereas the other two materials exhibit more than one relaxation time. The activation parameters are calculated and are found to be strongly dependent on the position of the hydroxyl group, and in the case of the branched isomers, of the methyl group. These results are compared with those in the literature for similar octanol isomers, and are discussed in terms of their dependence on liquid structure. The existence of closely ordered and loosely ordered chains is proposed to explain the results.
Measured values of density and dielectric permittivity have been fitted to polynomial expressions in pressure and temperature. These are shown to reproduce measured values of density to within 0.25%. The polynomials are readily manipulated to give analytical expressions for thermodynamic constants, including the velocity of sound. Such constants are compared with values in the literature.
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