BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//CERN//INDICO//EN
BEGIN:VEVENT
SUMMARY:Quantum chemical study of methanol interaction with a pyrene-based
  acid
DTSTART;VALUE=DATE-TIME:20260922T141500Z
DTEND;VALUE=DATE-TIME:20260922T142000Z
DTSTAMP;VALUE=DATE-TIME:20260914T040402Z
UID:indico-contribution-552@indico.bitp.kiev.ua
DESCRIPTION:Speakers: Oksana Kremen (Chuiko Institute of Surface Chemistry
  of National Academy of Sciences of Ukraine)\n**Quantum chemical study of 
 methanol interaction with a pyrene-based acid**\n\n*Kremen O. S.1\, Bychko
  I. B.2\, Nikolaienko T.Y.3\, Lobanov V. V.1\, Strizhak P. E.2*\n\n1Chuiko
  Institute of Surface Chemistry of the NAS of Ukraine\, \nOleh Mudrak Str.
 \, 17\, Kyiv-03164\, Ukraine\, kremenoksana@ukr.net\n2L. V. Pisarzhevskii 
 Institute of Physical Chemistry of the NAS of Ukraine\, \nProspect Nauki\,
  31\, Kyiv-03028\, Ukraine\n3Taras Shevchenko National University of Kyiv\
 , Faculty of Physics\, \nVolodymyrska Str.\, 64/13\, Kyiv 01601\, Ukraine*
 \n\nThe conversion of methanol (MeOH) to dimethyl ether (DME) is a large-s
 cale industrial process\, and developing advanced catalysts to reduce cost
 s is important. Oxygen-containing carbons are promising metal-free catalys
 ts for many reactions\; therefore\, this report presents quantum-chemical 
 calculations (DFT\, M062X/6-31G**/D3\, ORCA 6.0.0) of the interaction betw
 een MeOH and pyrene-based acid (Pyr) in the gas phase at T = 0 K to elucid
 ate the initial interaction mechanism for further investigation of the Met
 hanol-to-DME conversion.\n\nGeometry optimisation yielded two acid isomers
  (A and B)\, depending on the orientation of the –COOH group plane relat
 ive to the aromatic plane. The –COOH group was covalently bonded to the 
 terminal hexagonal carbon atom (alpha carbon) of the Pyr molecule (instead
  of a hydrogen atom) in the so-called syn conformation (where the O=C–O
 –H dihedral angle (θ) is defined to be 0°). Isomer A has a more twiste
 d –COOH group relative to the aromatic core (θ=19.96°) than isomer B (
 θ=0.82°)\, due to the asymmetry of the carbon skeleton. The total energy
  of the planar B-Pyr acid is lower by 5.95 kJ/mol than that of the twisted
  A-Pyr acid molecule.\n\nBader's Quantum Theory of Atoms in Molecules was 
 used to identify the presence or absence of intramolecular hydrogen bonds 
 (HB) in Pyr. The topological analysis of the electron density distribution
  confirmed the presence of two intramolecular HBs in the B-Pyr (between O 
 atoms of the –COOH group and H atoms of the aromatic core)\, as evidence
 d by the presence of the corresponding bond critical points (BCPs) of type
  (3\, −1). In contrast\, only a single intramolecular HB was observed in
  the A-Pyr acid (between the O atom of the –OH group and the hydrogen at
 om of the aromatic core). Despite the C=O···H–C length being 2.361 Å
  (less than the sum of the van der Waals radii of the O and H atoms\, whic
 h is 2.5 Å)\, there are no BCPs according to Bader’s analysis. Two poss
 ible ways of MeOH interaction with the B-Pyr acid are considered: formatio
 n of a cyclic complex (CC) and attack of the –C=O of the Pyr by MeOH. Th
 e CC is stabilised by two intermolecular HBs\, forming a six-membered ring
  (6MR) between the –COOH group atoms of the Pyr acid and the –OH group
  atoms of the MeOH molecule. The interaction energy is –66.48 kJ/mol. Th
 e CC have two tautomeric forms (causing asymmetry in the carbon skeleton)\
 , more twisted CCa and CCb\, which can interconvert through an activation 
 barrier of 42.40 kJ/mol. The transition state (TS) for the transition betw
 een CCa and CCb structural isomers is characterised by a flip-flop switchi
 ng of a hydrogen atom between adjacent acceptor centres (two O atoms of th
 e –COOH group and one O atom of the MeOH)\, forming a two-sided hydrogen
  trap. The configuration of CCb is thermodynamically more stable than CCa\
 , since its formation energy is lower by 4.43 kJ/mol.\n\nIn the second pat
 hway\, the MeOH molecule attacks the C=O bond of the Pyr\, forming a tetra
 hedral structure because the carbon atom orbitals in the –COOH group cha
 nge hybridisation from sp2 to sp3. This atom is bound to four substituents
 : a Pyr-based group (–C16H9)\, two –OH groups and a single methoxy gro
 up (–OCH3). The analysis of the atomic vibrations for the cyclic four-me
 mbered TS structure confirmed the presence of a single imaginary frequency
  at i1620.70 cm–1. The activation barrier is +169.01 kJ/mol\, and the ad
 sorption energy is +23.88 kJ/mol.\n \nBased on the obtained energetic para
 meters\, it was established that the bonding of the MeOH molecule preferen
 tially proceeds via the formation of 6MR CC structures\, as this pathway i
 s significantly more energetically favourable than direct attack on the C=
 O bond of the –COOH group.\n\nThis research was partially funded by the 
 National Research Foundation of Ukraine (grant 2023.03/0041).\n\nhttps://i
 ndico.bitp.kiev.ua/event/18/contributions/552/
LOCATION:Bogolyubov Institute for Theoretical Physics Conference Hall
URL:https://indico.bitp.kiev.ua/event/18/contributions/552/
END:VEVENT
END:VCALENDAR