Kostiantyn Kulyk

Chirally sensitive collision induced dissociation of proton‐bound diastereomeric complexes of tryptophan and 2‐butanol

In this work we report the stereo-dependent collision-induced dissociation (CID) of proton-bound complexes of tryptophan and 2-butanol. The dissociation efficiency was measured as a function of collision energy in single collision mode. The homochiral complex was found to be less stable against CID than a heterochiral one. Additional gas dependence measurements were performed with diastereomeric complexes that confirm the findings.

Low-Energy Collisions of Protonated Enantiopure Amino Acids with Chiral Target Gases

AbstractHere we report on the gas-phase interactions between protonated enantiopure amino acids (l- and d-enantiomers of Met, Phe, and Trp) and chiral target gases [(R)- and (S)-2-butanol, and (S)-1-phenylethanol] in 0.1–10.0 eV low-energy collisions. Two major processes are seen to occur over this collision energy regime, collision-induced dissociation and ion-molecule complex formation. Both processes were found to be independent of the stereo-chemical composition of the interacting ions and targets. These data shed light on the currently debated mechanisms of gas-phase chiral selectivity by demonstrating the inapplicability of the three-point model to these interactions, at least under single collision conditions. Graphical Abstract

Kinetics of Valeric Acid Ketonization and Ketenization in Catalytic Pyrolysis on Nanosized SiO2, γ-Al2O3, CeO2/SiO2, Al2O3/SiO2 and TiO2/SiO2

Valeric acid is an important renewable platform chemical that can be produced efficiently from lignocellulosic biomass. Upgrading of valeric acid by catalytic pyrolysis has the potential to produce value added biofuels and chemicals on an industrial scale. Understanding the different mechanisms involved in the thermal transformations of valeric acid on the surface of nanometer-sized oxides is important for the development of efficient heterogeneously catalyzed pyrolytic conversion techniques. In this work, the thermal decomposition of valeric acid on the surface of nanoscale SiO2 , γ-Al2 O3 , CeO2 /SiO2 , Al2 O3 /SiO2 and TiO2 /SiO2 has been investigated by temperature-programmed desorption mass spectrometry (TPD MS). Fourier transform infrared spectroscopy (FTIR) has also been used to investigate the structure of valeric acid complexes on the oxide surfaces. Two main products of pyrolytic conversion were observed to be formed depending on the nano-catalyst used-dibutylketone and propylketene. Mechanisms of ketene and ketone formation from chemisorbed fragments of valeric acid are proposed and the kinetic parameters of the corresponding reactions were calculated. It was found that the activation energy of ketenization decreases in the order SiO2 >γ-Al2 O3 >TiO2 /SiO2 >Al2 O3 /SiO2 , and the activation energy of ketonization decreases in the order γ-Al2 O3 >CeO2 /SiO2 . Nano-oxide CeO2 /SiO2 was found to selectively catalyze the ketonization reaction.

Non-statistical fragmentation of large molecules in collisions with atoms

Non-statistical fragmentation processes are important when Polycyclic Aromatic Hydrocarbon (PAH) molecules, fullerenes, or other large molecules collide with atoms at center- of-mass energies from a few tens to a few hundreds of eV. The typical result is the prompt, billiard-ball-like knockout of single atoms (CHx-loss). This is distinct from the well-known statistical fragmentation patterns of these molecules, which are dominated by H- and C2H2-loss for PAHs and C2-loss for fullerenes. We have explored the role of non-statistical fragmentation of PAHs and fullerenes in a series of experimental and theoretical studies. In general, the yield of non-statistical fragments depends sensitively on their stability against secondary statistical fragmentation following knockout.

Fragmentation of anthracene C₁₄H₁₀, acridine C₁₃H₉N and phenazine C₁₂H₈N₂ ions in collisions with atoms.

We report experimental total, absolute, fragmentation cross sections for anthracene C14H10, acridine C13H9N, and phenazine C12H8N2 ions colliding with He at center-of-mass energies close to 100 eV. In addition, we report results for the same ions colliding with Ne, Ar, and Xe at higher energies. The total fragmentation cross sections for these three ions are the same within error bars for a given target. The measured fragment mass distributions reveal significant contributions from both delayed (≫10(-12) s) statistical fragmentation processes as well as non-statistical, prompt (∼10(-15) s), single atom knockout processes. The latter dominate and are often followed by secondary statistical fragmentation. Classical Molecular Dynamics (MD) simulations yield separate cross sections for prompt and delayed fragmentation which are consistent with the experimental results. The intensity of the single C/N-loss peak, the signature of non-statistical fragmentation, decreases with the number of N atoms in the parent ion. The fragment intensity distributions for losses of more than one C or N atom are rather similar for C14H10 and C13H9N but differ strongly for C12H8N2 where weak C-N bonds often remain in the fragments after the first fragmentation step. This greatly increases their probability to fragment further. Distributions of internal energy remaining in the fragments after knockout are obtained from the MD simulations.

Interactions of amino acid enantiomers with chiral target in high and low energy collisions

The study is focused on investigation of stereospecific interaction of amino acid enantiomers with chiral targets in collisions of 1 keV and ~ 1 eV energy using tandem mass spectrometry.