Field induced changes in the ring/chain equilibrium of hydrogen bonded structures: 5-methyl-3-heptanol

abstract: Using non-linear dielectric techniques, we have measured the dynamics of 5-methyl-3-heptanol at a temperature at which the Kirkwood correlation factor g[subscript K] indicates the coexistence of ring- and chain-like hydrogen-bonded structures. Steady state permittivity spectra recorded in the presence of a high dc bias electric field (17 MV/m) reveal that both the amplitude and the time constant are increased by about 10% relative to the low field limit. This change is attributed to the field driven conversion from ring-like to the more polar chain-like structures, and a direct observation of its time dependence shows that the ring/chain structural transition occurs on a time scale that closely matches that of the dielectric Debye peak. This lends strong support to the picture that places fluctuations of the end-to-end vector of hydrogen bonded structures at the origin of the Debye process, equivalent to fluctuations of the net dipole moment or g[subscript K]. Recognizing that changes in the ring/chain equilibrium constant also impact the spectral separation between Debye and α-process may explain the difference in their temperature dependence whenever g[subscript K] is sensitive to temperature, i.e., when the structural motifs of hydrogen bonding change considerably.This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in The Journal of Chemical Physics and may be found at http://aip.scitation.org/doi/10.1063/1.4961022