Supramolecular Structure of Phenyl Derivatives of Butanol Isomers

Abstract

Wide-angle X-ray scattering patterns were recorded for a series of aliphatic butanol isomers ( n -, iso -, sec -, tert -butanol) and their phenyl derivatives (4-phenyl-1-butanol, 2-methyl-3-phenyl-1-propanol, 4-phenyl-2-butanol, and 2-methyl-1-phenyl-2-propanol, respectively) to determine their atomic-scale structure with particular emphasis on the formation of supramolecular clusters. In addition, molecular dynamics simulations were carried out and yielded good agreement with experimental data. The combination of experimental and theoretical results allowed clarification of the origin of the pre-peak appearing at low scattering angles for the aliphatic butanols and its absence for their phenyl counterparts. It was demonstrated that the location of the hydroxyl group in the molecule of alkyl butanol, its geometry, and rigidity determine the morphology of the supramolecular clusters, while the addition of the aromatic moiety causes more disordered organization of molecules. The phenyl group significantly decreases the number of hydrogen bonds and size of the supramolecular clusters formed via the O–H···O scheme. The lower association ability of phenyl alcohols via H-bonds is additionally attenuated by the appearance of competing π–π configurations evidenced by the structural models.

Nature of Dielectric Response of Phenyl Alcohols

“…It is quite surprising result as many mechanical data available in the literature for various MA clearly report an emerging of additional relaxation process slower than the α-mode (or a crossover from an intermediate to the terminal power law) for these materials. − This process was considered as evidence of an additional slow dynamics of supramolecular structures (analogous to the dielectric Debye relaxation). One can assume that the observed herein behavior typical for nonassociating liquids might be a result of the presence of phenyl group, leading to the formation of relatively small associates (which do not affect mechanical properties of examined PhAs). , Alternatively, one can postulate that this additional mechanical process might be not resolved due to a time scale similar to that of the α-mode. Note that studies on a series of octanol structural isomers ( x -methyl-3-heptanol, where x = 2–6) shown that the separation between both observed mechanical processes increases with an increasing distance between the methyl and hydroxyl groups (due to affecting the morphology, but not population, of associates) …”

Experimental and Computational Approach to Studying Supramolecular Structures in Propanol and Its Halogen Derivatives

“…Molecular dynamics simulations were carried out using the GROMACS package (version 2020). − Interactions in the systems were described using the general AMBER force field (GAFF) and topology provided by AmberTool21 . The simulation parameters were adopted the same as in our previous paper . Structure factors were calculated based on the optimized models of spatial arrangement of molecules (2000 molecules) using of the TRAVIS software. − …”

“…It is commonly observed in dielectric measurements of aliphatic MAs, irrespective of the position of hydroxyl units in the molecule. − According to the current knowledge, the dynamic properties of the D process for associating liquids are an emanation of their complex internal structure driven by the formation of various supramolecular clusters through hydrogen bonds (HBs). However, the exact molecular origin of this characteristic polarization decay is still yet to be addressed. ,− Herein one can briefly mention that there are several possible explanations for the nature of this process. − Among them, the transient chain model (TCM) proposed by Gainaru and co-workers provides the most commonly accepted description of the molecular origin of the D relaxation. The model postulates that the D mode appears due to changes in the dipole moment associated with the attachment and detachment of molecules to the ends of the H-bonded chains.…”

On the relationship between the Debye process in dielectric response and a dissociation–association phenomenon in phenyl alcohols

“…This suggests the formation of mainly y dimers or trimers in the investigated systems. 31,42 In Fig. 3, we plotted the temperature dependences of both Debye, t D , and structural, t a , relaxation times determined for all examined PhAs.…”