THE P,T-DEPENDENCE OF SELF-DIFFUSION IN LIQUID 1-PENTANOL, 2-PENTANOLAND 3-PENTANOL

The self diffusion of the three alcohols with the n-pentane carbon ske leton has been studied as function of temperature and pressure. The te mperature was varied from 470 K into the deeply supercooled range. The maximum pressure reached was 200 MPa. In order to study the influence of the isotopic substitution upon the molecular dynamics, the three i sotopomers with deuterons in the hydroxyl position were also investiga ted. Contrary to the situation for ethanol and the two propanols, no d ynamic isotope effect is observed when the pairs of the deuterated and the protonated alcohols are compared. The T, p-dependence of the self diffusion is well characterized by the VTF-equation. Application of t he rough hard sphere model demands a rotation translation coupling par ameter that decreases rapidly with falling temperature.