Monohydroxy Alcohols Research Articles

High electric fields elucidate the hydrogen-bonded structures in 1-phenyl-1-propanol

High electric fields are applied to illuminate the role of hydrogen bonding in the dielectric relaxation of 1-phenyl-1-propanol (1P1P). Unlike many other monohydroxy alcohols, 1P1P is not associated with a strong distinct Debye loss peak, which would indicate chain-like hydrogen-bonded structures. We exploit the feature that a high field induced enhancement of the dielectric constant indicates a shift of the thermodynamic equilibrium towards more polar (e.g., chain-like) structures. This so-called ‘chemical effect’ rests on a field-induced lowering of the free energy of the more polar species, thus shifting the equilibrium towards a higher dielectric constant. We demonstrate that an external electrical field of EB = 245 kV cm−1 increases the amplitude of the Debye peak, whereas that of the remaining loss profile remains constant. This indicates the coexistence of chain-like and less polar structures in supercooled 1P1P and helps to discriminate the Debye process from the signature of the primary structural relaxation.

Savior in COVID-19 times turns killer: An autopsy based case report of isopropanol ingestion

Withdrawal symptoms amongst the habitual drinkers of alcohol have become a common finding during the COVID 19 pandemic as a result of lockdown. To curb the symptoms, some seek to take surgical spirit which contains isopropanol, a monohydroxy alcohol. As the mortality rate of its ingestion is very low, most of the literature is concerned with the clinical findings. Here we present autopsy findings of a couple who had consumed surgical spirit to ease the symptoms of alcohol withdrawal. On taking a history from the son we came to know about the withdrawal symptoms and previous medical treatment. They had consumed surgical spirit which they allegedly took to relieve the symptoms which had been retrieved from the house. There were no external injuries present over the bodies. The stomach showed diffuse submucosal hemorrhages. Lungs were grossly edematous and hemorrhagic. Urine showed the presence of ketone bodies. Chemical analysis of viscera showed the presence of isopropanol. Many studies pointed out that during the COVID-19 pandemic there is a surge in the withdrawal symptoms amongst the alcoholics which even had provoked them towards consumption of toxic alcohols. With limited or no access to alcoholic beverages, people tend to consume toxic alcohol to relieve their withdrawal symptoms. In these ‘hard times’ population at risk should be identified, treated, and counseled against the taking of toxic alcohols. Substitutes for alcohol-based sanitizers could be researched and put in use. A cautionary message should be boldly printed on the label of such things.

Ionic conductivity of monohydroxy alcohol liquids doped with known probe ions and analysis of the liquid structure

The specific values of the conductivity [Formula: see text] and its variation with temperature [Formula: see text] of 2-pentanol and 2-methyl-1-pentanol liquids doped with different concentrations of NaI (abbreviated as 2PEN-[Formula: see text]NaI and 2M1PEN-[Formula: see text]NaI, respectively) ([Formula: see text], 1% and 5%) are measured by the commercial equipment. The results show that whether NaI is doped or not, [Formula: see text] of 2PEN-[Formula: see text]NaI and 2M1PEN-[Formula: see text]NaI all have a conductivity peak in the range of 300–350 K different from that of typical glass-formers of small molecules. In addition, [Formula: see text] goes up with increasing [Formula: see text], and the temperature corresponding to [Formula: see text] maximum increases with rising NaI content. Moreover, there is a nonlinear behavior of [Formula: see text] with [Formula: see text], i.e., with rising [Formula: see text], [Formula: see text] decreases at low-temperatures, but increases at high-temperatures. Moreover, the liquid structure and its variation with [Formula: see text] are further analyzed based on the ionic conductivity.

Interplay between structural static and dynamical parameters as a key factor to understand peculiar behaviour of associated liquids

In this article, we have addressed fundamental relationships between the chemical structure, intermolecular order, degree of the association and the dynamical properties, including the nature of dielectric response function, the variation of the glass transition temperature and the Kirkwood factor in three homologues phenyl derivatives of monohydroxy alcohols: 1-phenyl-2-butanol, 4-phenyl-1-butanol, and 4-phenyl-2-butanol. Dielectric data supported by infrared and diffraction investigations allowed us to certify that the Debye relaxation can be detected not only in aliphatic but also aromatic monohydroxy alcohols, suggesting its universal character, irrespectively of the chemical structure and steric hindrance. Moreover, we discovered that besides water, 4-phenyl-1-butanol is a next H-bonded system that exhibits the Debye-like relaxation process and no sign of the diffraction pre-peak being a fingerprint of the medium-range intermolecular order. This finding alters our understanding of the molecular origin of the scattering pre-peak and Debye-type process in diffractograms and dielectric loss spectra, respectively. Finally, we revealed that the activation volume, which is a measure of the volume required for reorientational motions of molecules to occur, is the greatest for the system with the highest Kirkwood factor at the glass transition temperature. It means that except the static parameters characterising the size of the supramolecular associates, their morphology, and the degree of intermolecular order, also dynamical quantity related to the volume of relaxing supramolecular structures is required to understand the fluctuations in the Kirkwood factor, and generally, the behaviour of associating liquids at varying thermodynamic conditions.

Dipole-dipole correlations and the Debye process in the dielectric response of nonassociating glass forming liquids.

The nonexponential shape of the α process observed in supercooled liquids is considered as one of the hallmarks of glassy dynamics and has thus been under study for decades, but is still poorly understood. For a polar van der Waals liquid, we show here-in line with a recent theory-that dipole-dipole correlations give rise to an additional process in the dielectric spectrum slightly slower than the α relaxation, which renders the resulting combined peak narrower than observed by other experimental techniques. This is reminiscent of the Debye-process found in monohydroxy alcohols. The additional peak can be suppressed by weakening the dipole-dipole interaction via dilution with a nonpolar solvent.

Are hydrogen supramolecular structures being suppressed upon nanoscale confinement? The case of monohydroxy alcohols

In this paper, the molecular dynamics, H-bonding pattern and wettability of the primary and secondary monohydroxyalcohols, 2-ethyl-1-hexanol (2E1H), 2-ethyl-1-butanol (2E1B) and 5-methyl-3-heptanol (5M3H) infiltrated into native and functionalized silica and alumina pores having pore diameters, d = 4 nm and d = 10 nm, have been studied with the use of Broadband Dielectric (BDS) and Fourier Transform InfraRed (FTIR) spectroscopies, as well as contact angle measurements. We found significant differences in the behavior of alcohols forming chain- (2E1H, 2E1B) or micelle-like (5M3H) supramolecular structures despite of their similarities in the wettability and interfacial energy. It turned out that nanoassociates as well as H-bonds are more or less affected by the confinement dependently on the chemical structure and alcohol order. Moreover, a peculiar behavior of the self-assemblies at the interface was noted in the latter material (5M3H). Finally, it was found that irrespectively to the sample, type of pores, functionalization, the temperature evolution of Debye relaxation times, τD, of the confined systems deviates from the bulk behavior always at similar τD due to vitrification of the interfacial layer. This finding is a clear indication that unexpectedly dynamics (mobility) of the supramolecular structures close to the hydrophilic and hydrophobic surfaces is similar in each system.

High pressure dielectric study of N-ethylacetamide

As a step toward better understanding of the Debye-like response in N-ethylacetamide (NEA), we performed the broadband dielectric measurement of NEA under high pressure (up to p = 968 MPa). Currently, the prevailing opinion of an intense Debye-like relaxation in N-mono-substituted amides is that it originates from the slow dynamics of hydrogen-bonded supramolecular structures analogous to the Debye-like peak observed in monohydroxy alcohols. However, our results revealed that the high pressure behavior of NEA is different from that of monohydroxy alcohols. In contrast to monohydroxy alcohols, we found that the shape of dielectric loss spectra of NEA was unaffected by compression. In the light of these results, further critical discussion is required in order to improve our understanding of relaxation properties of NEA.

Hydrogen Bonding in the Liquid State of Linear Alcohols: Molecular Dynamics and Thermodynamics.

Linear monohydroxy alcohols are strongly hydrogen-bonded liquids that are considered to be homologues of water. Here, we report ab initio molecular dynamics simulations of the liquid alcohols, methanol to pentanol, and from the combined radial-angular probability distribution of the intermolecular O···O distances and HO···O angles determine the geometrical parameters that define the hydrogen bonds in these systems. The key feature of hydrogen bonds in the liquid alcohols, irrespective of the size of the alkyl group, is the strong orientation dependence with the donor-acceptor HO···O angle being close to zero, similar to that observed in liquid water. Hydrogen bond formation is consequently considered to be the passage from a state where donor-acceptor pairs show no preferred orientation to one where they are almost linear. The potential of mean force, the reversible work associated with this process, is computed from the pair probability density distributions obtained from the simulations and that for a hypothetical state where donor-acceptor pairs are randomly oriented. We find that the magnitude of the free energy for hydrogen bond formation is maximum for ethanol and show that this arises from a larger electrostatic contribution to hydrogen bond formation in ethanol as compared to the other alcohols.

Essential meaning of high pressure measurements in discerning the properties of monohydroxy alcohols with a single phenyl group

Three isomeric alcohols, 1-phenyl-2-butanol, 2-phenyl-1-butanol and 1-(4-methylphenyl)-1-propanol differentiated in terms of the position of phenyl ring and hydroxyl group, were the subject of molecular dynamic studies. The investigations carried out by means of broadband dielectric spectroscopy, mechanical spectroscopy and differential scanning calorimetry revealed numerous similarities such as surprising identity of temperature dependencies of relaxation times under atmospheric pressure conditions for 1-phenyl-2-butanol and 1-(4-methylphenyl)-1-propanol. However, these compounds are differentiated in terms of pressure characteristics of molecular dynamics. It has been shown that among many factors that may affect the obtained image, spatial packing of molecules and their stiffness are of key importance. Moreover, the conducted pressure measurements revealed that intermolecular bonding that exists for both compounds at ambient pressure, becomes markedly disturbed at elevated pressure, exceeding 500 MPa. Another important finding revealed in course of high-pressure investigations was the crystallization of 2-phenyl-1-butanol. It was found that this alcohol can be supercooled at ambient pressure, however after applying pressure it undergoes continuous crystallization. Thus it has been explicitly shown that measurements at high pressure conditions are of key importance for revealing the complex features of associated liquids.

Geometry of OHO interactions in the liquid state of linear alcohols from ab initio molecular dynamics simulations.

Monohydroxy alcohols are strongly associating liquids with the hydrogen bonding associated with the presence of the hydroxyl group having a significant influence on properties. Here we determine the geometry of the hydrogen bond in linear alcohols, methanol to pentanol, arising from intermolecular OHO interactions, from ab initio molecular dynamics trajectories by plotting the intermolecular non-bonded OHO and OO distances, and the ∠HOO (θ) angles for every possible pair of alcohol molecules in the ensemble. Two regions separate out in the scatter-plot; the one with short OHO and OO intermolecular distances and almost linear ∠HOO angles may be identified as the region where the intermolecular OHO geometry would be favorable for hydrogen bonding. We find that the geometry of the hydrogen bond arising from intermolecular OHO interactions in liquid alcohols shows little change with an increase in size of the alkyl group. This observation is in direct contrast to that in the crystalline state where marked departures in the HOO angle from linearity are seen with an increase in the alkyl chain on going from methanol to pentanol.

Influence of Molecular Architecture on the Dynamics of H-Bonded Supramolecular Structures in Phenyl-Propanols.

Relaxation behavior of monohydroxy alcohols (monoalcohols) in broadband dielectric spectroscopy (BDS) is usually dominated by the Debye process. This process is regarded as a signature of the dynamics of transient supramolecular structures formed by H-bonding. In phenyl-propanols, the steric hindrance of the phenyl ring is assumed to influence chain formation and thereby to decrease or even suppress the intensity of the Debye process. In the present paper, we study this effect in a systematic series of structural isomers of phenyl-1-propanol in comparison with 1-propanol. It turns out that by combining BDS, photon correlation spectroscopy (PCS), and calorimetry, the dynamics of supramolecular structures can be uncovered. While light scattering spectra show the same spectral shape of the main relaxation for all investigated monoalcohols, the dielectric spectra differ in the Debye contribution. Thus, it becomes possible for the first time to unambiguously disentangle both relaxation modes in the dielectric spectra. It turns out that the Debye relaxation becomes weaker, the closer the position of the phenyl ring is to the hydroxy group, in accordance with the analysis of the Kirkwood/Fröhlich correlation factor. Even in 1-phenyl-1-propanol, which has the phenyl group attached at the closest position to the hydroxy group, we can separate a Debye contribution in the dielectric spectrum. From this, we conclude that structure formation through hydrogen bonds is not generally suppressed by the increased steric hindrance of the phenyl ring, but rather an equilibrium of ring and chain-like structures is shifted toward ring-like shapes on shifting the phenyl ring closer to the hydroxy group. Moreover, the shape of the α-relaxation, as monitored by PCS, is the same as the self-part of the correlation in BDS, remains unaffected by the degree of hydrogen bonding and is the same among the investigated alcohols.

Explanation of the difference in temperature and pressure dependences of the Debye relaxation and the structural α-relaxation near Tg of monohydroxy alcohols

Advance was made recently in identifying the nature of the Debye relaxation observed by dielectric spectroscopy in monohydroxy alcohols by other experimental techniques. Consistent with the experimental findings, the transient chain model give a good description of the origin of the Debye relaxation. Notwithstanding, a general property of the Debye relaxation remains not explained, and that is the weaker temperature and pressure dependences of its relaxation time τD(T,P) compared to τα(T,P) of the faster structural α-relaxation at temperatures approaching the glass transition temperature Tg. Based on the transient chain model for the Debye relaxation, and the Coupling Model for the α-relaxation, we have explained the difference in the temperature and pressure dependences of τD(T,P) compared to τα(T,P) quantitatively.

New model of dielectric strength of Debye relaxation in monohydroxy alcohols

The Debye relaxation of dielectric spectroscopy exists extensively in monohydroxy alcohols, and the existing theory of the dielectric strength is obviously inconsistent with the experimental results. In this paper, we propose an Ising model of infinite free-rotating pseudospin chains and get the exact solution of the dielectric strength versus temperature. The model predictions are qualitatively consistent with the experimental results, especially the crossover from the low to the high-temperature Curie–Weiss law. The quantitative comparisons indicate that the model predictions can agree well with the experimental data below 250 K.

Spontaneous Polarization of Cryo-Deposited Films for Five Normal Saturated Monohydroxy Alcohols, CnH2n+1OH, n = 1-5.

Vapor-deposited films of neutral polar molecules on cold surfaces exhibit spontaneous electric polarization across the faces of the film. We deposited known amounts of the first five members of the normal monohydroxy alcohols at substrate temperatures in the range of 30-130 K. It is known that voltages measured are proportional to film thickness and that the effect is substrate-independent. The main trend observed was that the voltage per molecule surface density grows with molecule size and drops with deposition temperature. With the exception of some high-temperature methanol depositions, the films had a negative voltage on the vacuum side. Furthermore, the heavier members (1-butanol and 1-pentanol) showed reduced voltages for the lowest temperatures, suggesting that all members of the series could follow this pattern at temperatures below what was experimentally accessible. After deposition, film voltage was monitored during a temperature ramp showing first an increase in the voltage measured, then gradual decay before film evaporation. Initial film voltages are in general agreement with the concept of surface mobility of vapor-deposited molecules and indicate a negative correlation with dipole moment size.

Modelling Debye Dielectric Relaxation in Monohydroxy Alcohols**Supported by the National Natural Science Foundation of China under Grant No 11664042.

The Debye relaxation of dielectric spectroscopy exists extensively in monohydroxy alcohols. We model the relaxation based on the infinite-pseudospin-chain Ising model and the Glauber dynamics, and the corresponding complex permittivity is obtained. The model results are in good agreement with the experimental data of 3,7-dimethyl-1-octanol, 2-ethyl-1-hexanol and 5-methyl-2-hexanol in a wide temperature range. Moreover, in the model parameters, the sum of the mean-field interaction energy and two times the orientation is nearly twice the hydrogen bond energy, which further states the rationality of this model.

Measurements and analyses of the conductivities of probe ions in monohydroxy alcohol liquids

The conductivities (σ) of probe ions in three kinds of monohydroxy alcohol liquids, 2-pentanol, 2-methyl-1-propanol, and 2-methyl-1-pentanol, were measured in the temperature (T) range of 150–375 K. The results show that, with increasing T, σ increases first and then decreases, which is obviously different from the monotonically exponential increase in the typical glass-forming liquid, glycerol. The temperatures (Tσ) corresponding to the maximum σ values are 297, 338, and 300 K, respectively. By comparison with the typical glass-forming liquid, glycerol, it is concluded that Tσ is the crossover temperature between the promotion by thermal activation and the hindrance of the ion motion coming from the interspace reduction among the hydrogen bonding molecular chains due to the decrease of the chain length as T goes up. σ vs T satisfies a phenomenological equation with a modifying factor originating from the hindrance.

Linear and nonlinear shear studies reveal supramolecular responses in supercooled monohydroxy alcohols with faint dielectric signatures.

Monohydroxy alcohols (MAs) with methyl and hydroxyl side groups attached to the same carbon atom in the alkyl backbone can display very weak structural and supramolecular dielectric relaxation processes when probed in the regime of small electrical fields. This can render their separation and assignment difficult in the pure liquids. When mixing with bromoalkanes, a faint Debye-like process can be resolved dielectrically for 4-methyl-4-heptanol. To achieve a separation of structural and supramolecular processes in pure 4-methyl-4-heptanol and 3-methyl-3-heptanol, mechanical experiments are carried out in the linear-response regime as well as using medium-angle oscillatory shear amplitudes. It is demonstrated that first-order and third-order nonlinear mechanical effects allow for a clear identification of supramolecular viscoelastic modes even for alcohols in which they leave only a weak signature in the linear-response shear modulus. Additionally, the nonlinear rheological behavior of 2-ethyl-1-hexanol is studied, revealing that its linearly detected terminal mode does not coincide with that revealed beyond the linear-response regime. This finding contrasts with those for the other MAs studied in this work.

Local dielectric response in 1-propanol: α-relaxation versus relaxation of mesoscale structures.

The dielectric Debye relaxation in monohydroxy alcohols has been subject of long-standing scientific interest and is presently believed to arise from the relaxation of transiently H-bonded supramolecular structures. Therefore, its manifestation in a measurement with a local dielectric probe might be expected to be different from the standard macroscopic dielectric experiment. In this work we present such local dielectric measurements obtained by triplet state solvation dynamics (TSD) and compare the results with macroscopic dielectric and light scattering data. In particular, with data from an improved TSD setup, a detailed quantitative comparison reveals that the Debye process does not significantly contribute to the local Stokes shift response function, while α- and β-relaxations are clearly resolved. Furthermore, this comparison reveals that the structural relaxation has almost identical time constants and shape parameters in all three measurement techniques. Altogether our findings support the notion that the transiently bound chain structures lead to a strong cross-correlation contribution in macroscopic dielectric experiments, to which both light scattering and TSD are insensitive, the latter due to its local character and the former due to the molecular optical anisotropy being largely independent of the OH bonded suprastructures.

Inflection point in the Debye relaxation time of 2-butyl-1-octanol.

We report a striking anomaly in the pressure dependent Debye-relaxation time of the branched monohydroxy alcohol 2-butyl-1-octanol. Evidence of a crossover from slower to faster than exponential pressure dependency was obtained at different temperatures via high pressure broadband dielectric spectroscopy. At the same time, viscosity measurements reveal similar behavior in the viscosity, respectively, the structural relaxation time, indicating a similar origin of the phenomena.

Dynamics of two glass forming monohydroxy alcohols by field cycling 1H NMR relaxometry

The dynamics of 2,2-dimethylbutan-1-ol (2,2-DM-1-B) and 3,3-dimethylbutan-1-ol (3,3-DM-1-B), two glass forming monohydroxy alcohols, was investigated by field cycling 1H NMR relaxometry in their liquid phase, including the supercooled regime. Nuclear Magnetic Relaxation Dispersion (NMRD) curves (i.e. longitudinal relaxation rate R1vs1H Larmor frequency), acquired for the two alcohols at different temperatures in the 0.01-35 MHz frequency range, were analyzed in terms of suitable models for internal motions, overall molecular reorientations, and molecular self-diffusion, and the corresponding correlation times were quantitatively determined. In addition, trends of 1H R1 as a function of the frequency square root at low frequencies, where the contribution of translational motions dominates, were exploited to achieve an independent determination of the self-diffusion coefficients (D), which does not require the separation of different motional contributions to relaxation. Good agreement was found between D values determined by the two methods, thus corroborating the model used for the description of the NMRD curves. Self-diffusion was found to be slower and more strongly temperature dependent for 2,2-DM-1-B with respect to 3,3-DM-1-B, whereas molecular reorientations were quite similar for the two isomeric alcohols. Correlation times for molecular reorientations were found to be at least one order of magnitude shorter than those reported in the literature for the Debye-like relaxation observed by dielectric spectroscopy in the liquid phase.