Theoretical study on the mechanism of extraction reaction between silylene carbene and its derivatives and thiirane |
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Authors: | X H Lu X Che L Shi J F Han Z X Lian Y Q Li |
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Institution: | 1.School of Chemistry and Chemical Engineering,University of Jinan,Jinan, Shandong,P. R. China |
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Abstract: | The mechanism of the sulfur extraction reaction between singlet silylene carbine and its derivatives and thiirane has been
investigated with density functional theory (DFT), including geometry optimization and vibrational analysis for the involved
stationary points on the potential energy surface. The energies of the different conformations are calculated by B3LYP/6-311G(d, p) method. From the potential energy profile, it can be predicted that the reaction pathway of this kind consists in two steps:
(1) the two reactants firstly form an intermediate through a barrier-free exothermic reaction; (2) the intermediate then isomerizes
to a product via a transition state. This kind of reactions has similar mechanism: when the silylene carbene and its derivatives
X2Si=C: (X = H, F, Cl, CH3)] and thiirane approach each other, the shift of 3p lone electron pair of S in thiirane to the 2p unoccupied orbital of C in X2Si=C: gives a p → p donor-acceptor bond, thereby leading to the formation of intermediate (INT). As the p → p donor-acceptor bond continues to strengthen (that is the C-S bond continues to shorten), the intermediate (INT) generates
product (P + C2H4) via transition state (TS). It is the substituent electronegativity that mainly affect the extraction reactions. When the
substituent electronegativity is greater, the energy barrier is lower, and the reaction rate is greater. |
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