Authors: Ping, Yin; Yucai, Hu; Xua, Yanbin; Jiang, Zhang; Zhongxi, Yu; Lin, Sun; Changrong, Bao

Source: Progress in Reaction Kinetics and Mechanism, Volume 32, Number 3, 2007 , pp. 153-164(12)

Publisher: Science Reviews 2000 Ltd

Abstract:

Theoretical studies on the thermodynamic and kinetic aspects of the reactions of Ti⁺ ion with the sulfur-transfer reagent SCO via the C—O bond activation pathway have been carried out over the temperature range 200-1200 K using the DFT/B3LYP method, general statistical thermodynamics and Eyring transition state theory with the Wigner correction. The relevant reactions comprise:

reaction 1

²Ti⁺+SCO→²IM₁→²TS₁→²IM₂ (Step 1)

→²TS₂→²IM₃→²TiO⁺+¹CS (Step 2)

and

reaction 2

⁴Ti⁺+SCO→⁴IM₁→CP→²TS₂→²IM₃→²TiO⁺+¹CS

in which the spin multiplicity changes from the quartet state to the doublet state in the crossing region. It is concluded that the order of the equilibrium constants (K) and the reaction rate constants (k) are consistent with that of their corresponding exoergic energies Δ E and reaction barriers, respectively, and their differences at low temperature are larger than those at high temperature. Step 2 of reaction 1 is both thermodynamically and kinetically favoured over the entire temperature range. Moreover, both Reaction 1 and 2 are exothermic and proceed spontaneously in which their entropy increases, and the magnitudes of their thermodynamic constants all decrease with rising temperature. The calculated ΔH°, ΔG°, and ΔS° values of the two reactions are relatively similar. However, because reactants ⁴Ti⁺ and SCO have a lower energy than that of reactants ²Ti⁺ and SCO, it is Reaction 2, in which the quartet state is changed to the doublet state through intersystem crossing, should be seen as dominant.

Keywords: thermodynamic and kinetic properties; titanium(I) ion; sulfur-transfer reagent SCO; C-O bond activation

Document Type: Research article

DOI: http://dx.doi.org/10.3184/146867807X234239

Affiliations: 1: School of Chemistry and Materials Science, Ludong University, Yantai 264025, P. R. China

Publication date: 2007-09-18

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• Progress in Reaction Kinetics & Mechanism is an international journal for the quarterly publication of both in-depth reviews and research articles.

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