https://hdl.handle.net/20.500.11811/689 2026-04-11T06:04:49Z https://hdl.handle.net/20.500.11811/12872 Efficient Prediction of Mole Fraction Related Vibrational Frequency Shifts Blasius, Jan; Drysch, Katrin; Pilz, Frank Hendrik; Frömbgen, Tom; Kielb, Patrycja; Kirchner, Barbara While so far it has been possible to calculate vibrational spectra of mixtures at a particular composition, we present here a novel cluster approach for a fast and robust calculation of mole fraction dependent infrared and vibrational circular dichroism spectra at the example of acetonitrile/(R)-butan-2-ol mixtures. By assigning weights to a limited number of quantum chemically calculated clusters, vibrational spectra can be obtained at any desired composition by a weighted average of the single cluster spectra. In this way, peak positions carrying information about intermolecular interactions can be predicted. We show that mole fraction dependent peak shifts can be accurately modeled and, that experimentally recorded infrared spectra can be reproduced with high accuracy over the entire mixing range. Because only a very limited number of clusters is required, the presented approach is a valuable and computationally efficient tool to access mole fraction dependent spectra of mixtures on a routine basis. 2023-11-16T00:00:00Z https://hdl.handle.net/20.500.11811/12871 A Quantum Cluster Equilibrium Theory for Multi-Component Liquids Frömbgen, Tom; Drysch, Katrin; Zaby, Paul; Dölz, Jürgen; Ingenmey, Johannes; Kirchner, Barbara In this work, we present a new theory to treat multi-component liquids based on quantum-chemically calculated clusters. The starting point is the binary quantum cluster equilibrium theory that is able to treat binary systems. The theory provides one equation with two unknowns. In order to obtain another linearly independent equation, conservation of mass is used. However, increasing the amount of components leads to more unknowns and this requires linearly independent equations. We address this challenge by introducing a generalization of the conservation of arbitrary quantities, accompanied by a comprehensive mathematical proof. Furthermore, a case study for the application of the new theory to ternary mixtures of chloroform, methanol and water is presented. Calculated enthalpies of vaporization for the whole composition range are given, and populations or weights of the different clusters are visualized. 2024-02-19T00:00:00Z https://hdl.handle.net/20.500.11811/10549 Acid-Catalyzed Rearrangements of 3-Aryloxirane-2-Carboxamides: Novel DFT Mechanistic Insights Qu, Zheng-Wang; Zhu, Hui; Katsyuba, Sergey; Mamedova, Vera L.; Mamedov, Vakhid A.; Grimme, Stefan Efficient synthesis of 3-arylquinolin-2(1H)-ones and N-(2-carboxyaryl)-oxalamides from protic acid-catalyzed rearrangements of 3-aryloxirane-2-carboxamides was achieved recently but not well understood. In contrast to the classical Meinwald rearrangement, extensive DFT calculations reveal that the proximal aryl and amide groups have strong synergetic effects to control the amide-aided and aryl-directed oxirane-opening and further rearrangement sequences. The ortho-nitro substituent of the proximal aryl is directly involved in a nucleophilic oxirane ring-opening, the amide C=O is an important proton shuttle for facile H-shifts, while the N-aryl may act as a potential ring-closing site via Friedel-Crafts alkylation. The mechanistic insights are useful for rational design of novel synthesis by changing the aryl and amide functional groups proximal to the oxirane ring. 2020-07-01T00:00:00Z https://hdl.handle.net/20.500.11811/10547 Regenerated Hoof Keratin from 1-Ethyl-3-Methylimidazolium Acetate and Insights into Disulfide-Ionic Liquid Interactions from MD Simulation Apostolidou, Christina Regeneration of the hoof keratin from ionic liquids was never successful in the past because the ionic liquids were not strong enough. However, this biomaterial starts to play a central role for the preparation of biofilms in the future. In the present study, hoof keratin was regenerated for the first time from an ionic liquid by experiment and characterized by FTIR spectroscopy, Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM). As 1-Ethyl-3-methylimidazolium acetate is strong enough to dissolve hooves, which have a lot of disulfide bonds, a Molecular Dynamics (MD) simulation was performed with this ionic liquid and diphenyl disulfide. The MD simulation reveals that not only the cation as postulated after experiments were carried out, but also the anion is very important for the dissolution process. This complete picture was and is not accessible via experiments and is therefore valuable for future investigations. The anion always interacts with the disulfide bond, whereas the cation prefers in some situations a strong H−O interaction with the anion. If the cations and the anions are separated from each other so that the cation can not interact with the anion, both interact with the disulfide bond. The high solvation power of this solvent is shown by the fact that the cation interacts from the left and right side and the anion from above and below the disulfide bond. 2020-06-08T00:00:00Z