Hydrogen-Bond Equilibria and Lifetimes in a Monohydroxy Alcohol

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.

Dielectric Spectroscopy in Ibuprofen-Dioxane Mixture

“…The presence of two relaxation processes in hydrogen-bonded systems in their supercooled regime is not new, similar behavior has been reported for monohydroxy alcohols [7][8][9][10][11][12][13][14][15] and also, recently observed in neat IBP [1,2]. As discussed above, in such systems, sterically hindered -OH group can limit the formation of hydrogen bond chain-like structures.…”

“…It is known for decades that several monohydroxy alcohols [7][8][9][10][11][12][13][14][15] and amides [16] hydrogen bonded glass forming systems results in intramolecular and intermolecular hydrogen bonding and behave differently. A study of monohydroxy alcohols reveals that hydrogen-bonded networks aggregate their polar -OH group in the chain or ring-like structures [9][10][11][12]. The aggregation of the chain-like structure shows a Debye relaxation, where the strength of Debye process depends on temperature, pressure, dilution, and confinement volume.…”

Nonlinear dielectric spectroscopy in a fragile plastic crystal

“…This implies an increase of the average dipolar moment of the sample material and thus explains the observed increase of ε s . In some respect this scenario resembles the nonlinear effects observed for the so-called Debye process of some monohydroxy alcohols: There stretched conformations of the hydrogen-bonded molecule clusters causing this process 36,37,38 were assumed to be preferred over ring-like structures when a high field is applied. 38,39 FIG.…”

Communication: Nonadditive dielectric susceptibility spectra of associating liquids

“…In addition, for x > 0 a distinct low-frequency feature gradually starts to evolve and for pure 4M3H it eventually turns into a resolved supramolecular Debye-like process. [18][19][20] As shown in Fig. 1(b) for x = 0.7 at several temperatures, the Debye-like process is separated by 3 decades from the peak that evolved (starting from x = 0) out of the α-relaxation.…”

“…16 In addition to an α-and β-process, these liquids feature a supramolecular low-frequency relaxation mode termed Debye-like process. 17 In the alcohol 4M3H, [18][19][20] this hydrogen-bonding driven mode is only weakly developed because the molecules organize themselves into almost closed rings. The consequent near cancelation of the total electric dipole moment generates only a small supramolecular relaxation strength.…”