Note: Molecular architecture dependent hydrogen-bonded motifs, entropy change, and dielectric permittivity of alcohols
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Our previous studies showed that the static permittivity, ɛs, of some octanol isomers first increased on cooling, then decreased, and finally increased rapidly, and ɛs monotonically increased on compression such that the local minimum in ɛs vanished. Thus, while ɛs is the same at different temperatures and pressures, the density differs. To reconcile these findings with thermodynamic requirements, we propose that hydrogen bonded ring-dimers of near zero dipole moment that form on initial cooling and decrease ɛs, open to form linear-dimers on further cooling (or pressurizing). The H and O atoms at the terminals of the linear dimer form hydrogen bonds with the existing monomers and linear chains, thus extending the length of the H-bonded chains. This mechanism agrees with the enthalpy and entropy of formation of ring-dimer and linear-chain motifs.
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