| Autor: |
Agieienko V; Laboratory of Engineering Chemistry, Research Institute for Chemistry, Lobachevsky State University of Nizhny Novgorod, 23 Gagarina av., 603022 Nizhny Novgorod, Russian Federation. vera.n.ageenko@gmail.com.; Nanotechnology and Biotechnology Department, Nizhny Novgorod State Technical University n.a. R.E. Alekseev, 24 Minina str., 603950 Nizhny Novgorod, Russian Federation., Buchner R; Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstraße 31, D-93040 Regensburg, Germany. |
| Jazyk: |
angličtina |
| Zdroj: |
Physical chemistry chemical physics : PCCP [Phys Chem Chem Phys] 2024 Jan 17; Vol. 26 (3), pp. 2312-2323. Date of Electronic Publication: 2024 Jan 17. |
| DOI: |
10.1039/d3cp05027k |
| Abstrakt: |
High-quality dielectric data for monoethanolamine (MEA)/water mixtures covering the entire miscibility range are presented. For MEA concentrations c 1 ≥ 1 M the obtained complex permittivity spectra, covering the frequency range from 0.05 to 89 GHz, are best described by a sum of four Debye relaxations. Modes at ∼3 GHz and ∼10 GHz are solute-specific. Whilst the first can be assigned to MEA aggregates, the second is a composite arising from "free" MEA dipoles with dynamically retarded water hydrating them. The relaxations at ∼18 GHz and ∼200 GHz essentially reflect the cooperative H-bond fluctuations of more-or-less unperturbed "bulk" water, albeit with minor solute contributions. Evaluation of the bulk-water amplitude reveals that in water-rich mixtures ( c 1 ≤ 3.5 M) Z t = 3.5 ± 0.2 H 2 O molecules hydrate a MEA molecule. Then Z t drops linearly, reaching zero for neat MEA. Supported by the literature, this concentration dependence suggests that only H 2 O molecules H-bonded to the NH 2 and OH groups of MEA contribute to Z t . At concentrations beyond hydration shell overlap ( c 1 ≥ 3.5 M) these H-bonds are gradually eliminated, while new interactions with neighboring MEA molecules are formed. From the evaluation of the MEA-specific amplitudes we conclude that for c 1 ≥ 2 M, including neat MEA, ∼35% of the solute molecules are in aggregates, where breaking the intermolecular NH⋯O hydrogen bond determines the dynamics. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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