Designing Green Chemical Avenues to Sequester and Metamorphosis of a Few Challenging Small Molecules by N-heterocyclic Carbene: Theoretical Investigations

Logdi, Ratan (2023) Designing Green Chemical Avenues to Sequester and Metamorphosis of a Few Challenging Small Molecules by N-heterocyclic Carbene: Theoretical Investigations. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Ratan Logdi (16RS053)) 16RS053.pdf - Submitted Version Restricted to Repository staff only Download (13MB)

Abstract

Small molecules like SOx, COx and NOx (x = 1, 2) etc. are harmful to the environment and human health. Industrial and anthropogenic emissions of SOx and NOx exacerbate the atmospheric level of the SOx and NOx everyday. Therefore, the fixation of SOx and NOx are highly demandable. Conversion of atmospheric N₂ to NH₃ is a grand challenging scientific problem over many decades. The prime aim of the thesis is to sequester SO₂ and NO₂ to valued chemicals, capturing of N₂ and formation of NH₃ through computational approaches at ambient conditions. This thesis provides a guide and sequential approaches toward this direction. In Introduction chapter, the importance of SOx and NOx is discussed. Chapter 1 is dedicated to investigating whether carbenes are applicable for SO₂ sequestering or not. It reflected that three carbenes are able to form thermodynamically stable oxathiirane S-oxide derivatives and three carbenes can produce sulfene derivatives. The competitive reactivity of SO₂ and NO₂ with carbenes are tested in Chapter 2. The mechanistic investigation of carbene-SO₂ reaction affirms that oxathiirane S-oxide derivative forms a stable keto–SO adduct. Chapter 3 highlights the complete conversion of the captured SO₂ to thiocarbonyl S-oxide derivative. The thiocarbonyl S-oxide derivative is formed from oxathiirane S-oxide derivative using second NHC molecule like Frog’s hunting mechanism. Chapter 4 discusses N₂ fixation and NH₃ formation at room temperature. Chapter 5 deals with carbene–N₂ reaction analyzed at the electronic level employing a new technique termed as Molecular Handycam technique. In this technique, the IRC trapping method is employed along with an AIMD study to describe real-time electron flow of the reaction. The perspectives of the present research and the scope for future studies are described in Future Prospects.

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