Rate Coefficients for Intramolecular Homolytic Substitution of Oxyacyl Radicals at Sulfur

2013 ◽  
Vol 66 (3) ◽  
pp. 323 ◽  
Author(s):  
Heather M. Aitken ◽  
Sonia M. Horvat ◽  
Michelle L. Coote ◽  
Ching Yeh Lin ◽  
Carl H. Schiesser

It is predicted on the basis of ab initio and density functional calculations that intramolecular homolytic substitution of oxyacyl radicals at the sulfur atom in ω-alkylthio-substituted radicals do not involve hypervalent intermediates. With tert-butyl as the leaving radical, free energy barriers ΔG‡ (G3(MP2)-RAD) for these reactions range from 45.8 kJ mol–1 for the formation of the five-membered cyclic thiocarbonate (8) to 56.7 kJ mol–1 for the formation of the six-membered thiocarbonate (9). Rate coefficients in the order of 104–106 s–1 and 101–104 s–1 for the formation of 8 and 9, respectively, at 353.15 K in the gas phase are predicted at the G3(MP2)-RAD level of theory.

2002 ◽  
Vol 55 (12) ◽  
pp. 753 ◽  
Author(s):  
Sunggak Kim ◽  
Sonia M. Horvat ◽  
Carl H. Schiesser

Ab initio molecular orbital and density functional calculations predict that 1,5-homolytic translocation reactions involving silyl, germyl and stannyl groups between two alkyl carbon atoms, between alkoxy oxygen atoms, and between alkyl and allylic carbon atoms proceed via concerted mechanisms involving frontside substitution at the higher heteroatom involved; CCSD(T)/DZP//B3LYP/DZP calculations predict energy barriers ranging from 69 to 114 kJ mol–1 depending on the system involved.


2006 ◽  
Vol 110 (22) ◽  
pp. 7178-7188 ◽  
Author(s):  
Theo Kurtén ◽  
Markku R. Sundberg ◽  
Hanna Vehkamäki ◽  
Madis Noppel ◽  
Johanna Blomqvist ◽  
...  

2021 ◽  
Author(s):  
Yunjian Li ◽  
Hui Pan ◽  
Xing Ming ◽  
Zongjin Li

Abstract Dissolution of mineral in water is ubiquitous in nature and industry, especially for the calcium silicate species. However, the behavior of such a complex chemical reaction is still unclear at atomic level. Here, we show that the ab initio molecular dynamics and metadynamics simulations enable quantitative analyses of reaction pathways, and the thermodynamics and kinetics of calcium ion dissolution from the tricalcium silicate (Ca3SiO5) surface. The calcium sites with different coordination environment leads to different reaction pathways and free energy barriers. The low free energy barriers lead to that the detachment of calcium ions is a ligand exchange and auto-catalytic process. Moreover, the water adsorption, proton exchange and diffusion of water into the surface layer accelerate the leaching of calcium ions from the surface step by step. The discovery in this work thus would be a landmark for revealing the mechanism of cement hydration.


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