Conghao Deng

Theoretical studies on the structures and reactivity of silylenoids. III. The structures and isomerization of silylenoid H2SiNaF

The potential energy surface of the singlet silylenoid H2SiNaF has been examined by ab initio calculations. The 3-21G and 6-31G* basis sets were used for full geometry optimizations. Four equilibrium structures and three isomeric transition states were located. The calculations have shown that the structures with three-membered ring and p-complex form are the most stable, and that there are two basic structures in which silylenoid, H2SiNaF, exists and takes part in chemical reactions. The classical tetrahedral and σ-complex forms are also local minima, but should rearrange easily to the three-membered ring structure with minimal activation.

An inner-sphere reorganization model of hetero-exchange electron transfer reaction of diatomic reactants

Abstract An accurate theoretical scheme for obtaining directly the inner-sphere reorganization energies of the hetero-exchange electron transfer reactions from ionization potentials and electron affinities is first reported in this paper. Ionization potentials and electron affinities are alternatively obtained from the Rydberg spectroscopic data via a numerical procedure for some diatomic molecules. The inner-sphere reorganization energy values are calculated for the hetero-exchange electron transfer reactions (AB + CD+ → AB+ + CD) of diatomic molecules and are compared with those from other approximate methods.

Theoretical studies of carbenes and carbenoids. Structures and decompositions of carbenoids HXC=CLiF (X=H, F)

Abstract Structures and decomposition pathways of carbenoids HXC=CLiF (X=H, F) have been studied using the RHF/3-216 gradient method. H2C=CLiF has one detectable structure (1) and decomposes via FBW rearrangement. HFC=CLiF has two detectable structures (6 and 8) and decomposes via FBW rearrangement or cis β-elimination. The fluoro substituent yields a stable four-membered ring structure, stabilizes the three-membered ringstructures and retards FBW rearrangement.

Theoretical studies on the structures and reactivity of silylenoids. II: The reaction of H2SiLiCl with H2

Abstract The reaction of silylenoid, H 2 SiLiCl, with H 2 has been investigated by ab initio molecular orbital theory. The structures of the reactants and transitions state were optimized with STO-3G and 3-21G basis sets. The activation barriers of the reaction are 48.8 kcal/mol (STO-3G) and 39.5 kcal/mol (3-21G). The reaction of H 2 SiLiCl with H 2 resembles the insertion reaction of silylene SiH 2 with H 2 . The electronic energies. Mulliken populations, dipole moments od various structures are also given and analyzed.

Novel structure and ring-opening mechanism of cyclopropylidene lithium fluorocarbenoid

Abstract Cyclopropylidene lithium fluorocarbenoid is studied using the ab initio method. 3-21 G is used for geometry calculations and 6-31G * for energies. Its structure is characterized by an unconventional CLiF ring with all ligands of the carbene center in a cone. It isomerizes with a 6.7 kcal/mol barrier. The ring opening to allene occurs in a fashion of disrotation-conrotation with a 16.4 kcal/mol barrier. The reaction mechanism is the same as that of cyclopropylidene, but the transition state arrives earlier and the relative rotation direction of two methylene terminals changes later.

AN EXTENDED LCAC-SW QUANTUM SCATTERING STUDY ON THE ION-PAIR FORMATION REACTIONS

Abstract In this Letter the LCAC–SW method has been extended to study the reaction dynamics for ion-pair formation processes on an M+X2→M++X2− reaction system involving two potential energy surfaces, i.e., the covalence state (M+X2) and the ionic state (M++X2−), and their crossing effect. The working equations for calculating the state-to-state probability have been derived based on the above two-state model, and the collinear state-selected probabilities for M+I2→M++I2− (M=Na, K, Cs) ion-pair formation systems have been obtained.

Mechanism of the isomerization of azirinylidene to ketenimine

Abstract The isomerization of azirinylidene to ketenimine has been studied with RHF/6-31 G* gradient methods. The ring opening is via conrotation-disrotation, and retarded by the stable π bond in azirinylidene. The barrier is 46.3 kcal/mol and the released energy 46.7 kcal/mol. The Mobius-Huckel concept is extended to ring opening of the carbenes, which are Mobius type with 4 n electrons leading to transition states and Huckel type with 4 n +2 electrons thereafter, or vice versa. Azirinylidene and cyclopropylidene are typical examples of the former and latter cases, respectively.

Ab initio studies on the structures and isomerization of the carbenoids CH2LiX (X = F, Cl)

Abstract The potential energy surface of the singlet carbenoid H 2 CLiCl has been examined using ab initio methods including electron correlation. The 6–31G ∗ basis set was used for all geometry optimizations. Three equilibrium structures and two isometrc transition states were located, but only the lowest energy structure with a three-membered ring should be experimentally observable and take part in chemical reactions. In addition, CH 2 LiF has been re-examined and it was found that isomerization of the structure with p-complex form to the structure with three-membered ring form was more reasonable via a rotational transition state than an inversion transition state.