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Kinetics and Mechanism of 4,4-Dicyano 5-Ethyl 1,5-Heptadiene Reaction in Gas and Solution Phase; Theoretical Approach
, M.Sc. Thesis Sharif University of Technology ; Gholami, Mohammad Reza (Supervisor) ; Sajjadi, Ali Akbar (Co-Advisor)
Abstract
Kinetics and mechanism of 4,4-dicyano-5-ethyl-1,5-heptadiene rearrangement reaction, a pericyclic type reaction, were studied with ab initio calculations in gas and solution phases. This reaction is one of the cope rearrangement in which secondary kinetic isotope effect is observed. Theoretical study on these reactions showed that probability of radicalic mechanism is inconsiderable and reaction proceeds through out a concerted mechanism with cyclic transition state. Isotope effect was studied by replacement of H1, H2 and H4,H5 with deuterium. The isotope effect data confirmed the concerted mechanism. Solvent effects on this reaction were studied by CPCM model. Solvation energies at...
Carbon dioxide: A waste product in the catalytic cycle of α-ketoglutarate dependent halogenases prevents the formation of hydroxylated by-products
, Article Journal of Physical Chemistry B ; Volume 113, Issue 1 , 2009 , Pages 12-14 ; 15206106 (ISSN) ; Latifi, R ; Sharif University of Technology
American Chemical Society
2009
Abstract
We present the first density functional theory study on α-ketoglutarate dependent halogenase and focus on the mechanism starting from the iron(IV)-oxo species. The studies show that the high-valent iron(IV)-oxo species reacts with substrates via an initial and rate determining hydrogen abstraction that is characterized by a large kinetic isotope effect (KIE) of 26.7 leading to a radical intermediate. This KIE value is in good agreement with experimental data. The reaction proceeds via two-state reactivity patterns on competing quintet and septet spin state surfaces with close lying hydrogen abstraction barriers. However the septet spin radical intermediate gives very high barriers for...