Unconventional Catalysis in Organic Chemistry: a Computational Mechanistic Study

Mattioli, Edoardo Jun (2020) Unconventional Catalysis in Organic Chemistry: a Computational Mechanistic Study, [Dissertation thesis], Alma Mater Studiorum Università di Bologna. Dottorato di ricerca in Chimica, 32 Ciclo.
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Abstract

Catalysis plays a vital role in modern synthetic chemistry. However, even if conventional catalysis (organo-catalysis, metal-catalysis and enzyme-catalysis) has provided outstanding results, various unconventional ways to make chemical reactions more effective appear now very promising. Computational methods can be of great help to reach a deeper comprehension of these chemical processes. The methodologies employed in this thesis are Quantum-Mechanical (QM), Molecular Mechanics (MM) and hybrid Quantum-Mechanical/Molecular Mechanics (QM/MM) methods. In this abstract the results are briefly summarised. The first unconventional catalysis investigated consists in the application of Oriented External Electric Fields (OEEFs) to SN2 and 4e-electrocyclic reactions. SN2 reactions with back-side mechanism can be catalysed or inhibited by the presence of an OEEF. Moreover, OEEFs can inhibit back-side mechanism (Walden inversion of configuration) and promote the naturally unfavoured front-side mechanism (retention of configuration). Electrocyclic ring opening reaction of 3-substituted cyclobutene molecules can occur with inward or outward mechanisms depending on the nature of substituent groups on the cyclobutene structure (torquoselectivity principle). OEEFs can catalyse the naturally favoured pathway or circumvent the torquoselectivity principle leading to different stereoisomers. The second case study is based on Carbon Nanotubes (CNTs) working as nano-reactors: the reaction of ethyl chloride with chloride anion inside CNTs was investigated. In addition to the SN2 mechanism, syn and anti-E2 reactions are possible. These reactions inside CNTs of different radii were examined with hybrid QM/MM methods, finding that these processes can be both catalysed and inhibited by the CNT diameter. The results suggest that electrostatic effects govern the activation energy variations inside CNTs. Finally, a new biochemical approach, based on the use of DNA catalyst was investigated at QM level. Deoxyribozyme 9DB1 catalyses the RNA ligation allowing the regioselective formation of the 3'-5' bond, following an addition-elimination two-step mechanism.

Abstract
Tipologia del documento
Tesi di dottorato
Autore
Mattioli, Edoardo Jun
Supervisore
Dottorato di ricerca
Ciclo
32
Coordinatore
Settore disciplinare
Settore concorsuale
Parole chiave
Oriented External Electric Fields; Carbon nanotubes; computational chemistry; QM ; QM/MM; DFT;
URN:NBN
Data di discussione
20 Marzo 2020
URI

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