Item – Theses Canada

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OCLC number
1006663190
Author
Sannigrahi, Mousumi,1970-
Title
Ab initio studies on reaction paths of the novel sulfur containing compounds : S₄², HCSNSCH, HCSNSN and FSSNSN⁺.
Degree
M. Sc. -- University of New Brunswick, 1994
Publisher
Ottawa : National Library of Canada = Bibliothèque nationale du Canada, 1995.
Description
2 microfiches
Notes
Includes bibliographical references.
Abstract
The energetics and formation of some sulfur containing homocyclic and heterocyclic systems have been studied using theoretical methods. Ab initio studies up to the MP2/6-31G* level were performed on the geometry and energy of S$\sb4\sp{2+}$. Eleven different isomers were considered. In the RHF/6-31G* method, the square structure was found to be most stable, followed by the trans-planar C$\sb{\rm 2h}$ structure. Minimum energy paths were calculated for the reaction $\rm2S\sb2\sp+ \to S\sb4\sp{2+}$, both in C$\sb{\rm 2v}$ and D$\sb{\rm 2h}$ symmetry. The transition state for both approaches was found to be a $\pi\sp*$-$\pi\sp*$ complex. CASSCF methods were used to recalculate the surface around the transition state to get a better estimate of the activation energy. Using the Woodward-Hoffmann rules, the reaction was shown to be symmetry-disallowed. In gas phase, the formation of the dication was found to be endothermic whereas in the solid state it is exothermic. This makes the reaction the first known example of a lattice-energy driven symmetry-disallowed reaction. The 1,3-dipolar-like cycloaddition of the SNS$\sp+$ cation to $\rm C\sb2H\sb2$, HCN and FSN has been studied in detail at the RHF/3-21G* and RHF/6-31G* level of theory. All of the above systems were found to undergo a retro-Diels Alder type of reaction where the triply bonded species is the electron donor. The reactions were found to be symmetry allowed and the principal interacting orbitals are the HOMO(triple bond) and LUMO(SNS$\sp+$). In each case the product was thermodynamically stable. (Abstract shortened by UMI.)
ISBN
031597009X
9780315970090