Hydrogen-bond equilibria and life times in a supercooled monohydroxy alcohol

TL;DR

This study investigates hydrogen-bond dynamics in supercooled 2-ethyl-1-hexanol using dielectric spectroscopy, NIR, and NMR, revealing that hydrogen-bond switching rates do not determine the main dielectric relaxation frequency.

Contribution

It provides new insights into the relationship between hydrogen-bond equilibria and dielectric relaxation in monohydroxy alcohols, challenging existing models.

Findings

Dielectric loss spectra span 13 decades in frequency.

Hydrogen-bond population correlates with dielectric amplitude.

Hydrogen-bond switching rate does not set the relaxation peak frequency.

Abstract

Dielectric loss spectra covering 13 decades in frequency were collected for 2-ethyl-1-hexanol, a monohydroxy alcohol that exhibits a prominent Debye-like relaxation, typical for several classes of hydrogen-bonded liquids. The thermal variation of the dielectric absorption amplitude agrees well with that of the hydrogen-bond equilibrium population, experimentally mapped out using near infrared (NIR) and nuclear magnetic resonance (NMR) measurements. Despite this agreement, temperature-jump NIR spectroscopy reveals that the hydrogen-bond switching rate does not define the frequency position of the prominent absorption peak. This contrasts with widespread notions and models based thereon, but is consistent with a recent approach.