Synthetic division and matrix factorization

Synthetic division is viewed as a change of basis for polynomials written under the Newton form. Then, the transition matrices obtained from a sequence of changes of basis are used to factorize the inverse of a bidiagonal matrix or a block bidiagonal matrix.     

Photoinduced hydrogen abstraction‐coupling reaction mechanism of Δ5‐steroids with substituted 1, 4‐benzoquinones via electron transfer pathways

The photochemical reaction between three A⁵‐steroids (1–3) and a series of substituted 1,4‐benzoquinones and their mechanistic study were reported. The reaction in nitrogen atmosphere led to the formation of three products including the steroid‐quinone coupling compound (A), 7‐hydroxy derivatives of Δ⁵‐steroids (B) and substituted 1, 4‐hydroquinone (C). Both chemical and spectrometric evidences such as UV‐Visible spectra, ESR, chemically induced dynamic nuclear polarization (CIDNP) and cyclic voltammetry (CV) verified that the title reaction underwent a predominant photoinduced electron transfer pathway via the triplet quinone.     

The gas‐phase H‐abstraction reactions of CCl3H with CX1X2•− (X1X2 = HF,HCl, HBr,HI, FF,ClCl, BrBr,and II), a DFT study

A systematic investigation on the H‐abstraction reactions of 8 carbene radical anions with CCl₃H has been performed theoretically using the popular DFT functional BHandHLYP/aug‐cc‐pVTZ/RECP level of theory. As a result, our studies strongly suggest that the reactivity of the title reactions (CX¹X^{2 ??} + CCl₃H) present increase in the order: CHI ^?? < CHBr ^?? < CHCl ^?? < CHF ^?? for first halogen CHX ^?? and CCI₂ ^?? < CBr₂ ^?? < CCl₂ ^?? < CF₂ ^?? for second halogen CX^{2 ??} , more important, the reactions of the former exhibit more activity than those of corresponding the latter. Moreover, based on the NBO analysis, the Activation Strain model analysis and the correlations analyses of activation barrier with both PA and IE, respectively, we further confirm over the conclusion. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

SYNTHESIS AND SOLUTION NMR-STUDIES OF THE TRIS(3,5-DIMETHYLPYRAZOL-1-YL) HYDROBORATOPALLADIUM(II) COMPLEX,Pd{(pz*)3BH}(PPh3)CI

Abstract

The sterically hindered tris(3, 5-dimethylpyrazol-l-yl)hydroborate complex of palladium, Pd{(pz*)₃BH}(PPh₃)Cl (1) has been prepared by the stepwise reaction of (CH₃CN)₂PdCl₂ with K{(pz*)₃BH}, and then PPh₃. The complex 1 has been fully characterized by microanalysis and various spectroscopic methods. A solution NMR study of 1 revealed that two pz* groups of the {(pz*)₃BH} ligand coordinate to palladium in cis positions, while the remaining group is not coordinated. VT NMR experiments have been performed to determine that signal broadening of the phenyl proton resonances in the ¹H-NMR spectrum is likely attributed to restricted rotation of the coordinated PPh₃ within the congested complex on the NMR time scale. Complex 1 was metastable in solution towards reaction with water to decompose into several uncharacterized species, in which a facile hydrolytic cleavage of the B-H bond proceeded as judged by IR and ¹H-NMR spectra of the products. Reaction of 1 with PPh₃ in CDCl₃ exclusively yielded cis-PdCl₂(PPh₃)₂, implicating a chlorine abstraction from the solvent.     

Coordination and Activation of the BF Molecule

No CO : Fluoroborylene (BF), isoelectronic with CO and N₂, can be trapped by a transition metal. The structurally characterized complex [{CpRu(CO)₂}₂(μ‐BF)] contains an unsupported bridging BF ligand, which is unprecedented in the structural chemistry of CO. With AlCl₃ , metal‐bound CO coordinates through the O atom without bond rupture, while the more polar and less π‐bonded BF ligand is heterolytically cleaved (see picture).

     

Quantum chemical study on insertion and abstraction reaction of dichlorocarbene with methyl alcohol and methyl mercaptan

The insertion and abstraction reaction mechanisms of singlet and triplet CCl₂ with CH₃MH (M=O, S) have been studied by using the DFT, NBO and AIM methods. The geometries of reactions, the transition state and products were completely optimized by B3LYP/6–311G(d, p). All the energy of the species was obtained at the CCSD(T)/6–311G(d, p) level. The calculated results indicated that the major pathways of the reaction were obtained on the singlet potential energy surface. The singlet CCl₂ can not only trigger the insertion reaction with C-H and M-H in four pathways, by which the products P1 [CH₃OCHCl₂, reaction I(1)], P3[Cl₂HCCH₂OH, reaction I(2)], P5[CH₃SCHCl₂, reaction II(1)] and P7[Cl₂HCCH₂SH, reaction II(2)] are produced respectively, but also abstract M-H, resulting P4 [CH₂O+CH₂Cl₂, reaction I(3)] and P8[CH₂S+CH₂Cl₂, reaction II(3)]. In addition, the important geometries in domain pathways have been studied by AIM and NBO theories. Supported by the National Natural Science Foundation of China (Grant No. 20335030) and Foundation of Education Committee of Gansu Province (Grant No. 0708-11)     

Thermodynamic and kinetic study of ibuprofen with hydroxyl radical: A density functional theory approach

Ibuprofen, a frequently detected pharmaceutical in natural and engineered waters, was studied in both neutral and anionic forms using density functional theory at the B3LYP/6‐311++G**//B3LYP/6‐31G* level of theory in its reaction with hydroxyl radical ( ? OH). The reaction pathways included ? OH addition to aromatic ring, abstraction of a H‐atom, and nucleophilic attack on the carbonyl group. The results showed that H‐atom abstraction pathways are the most favorable. The free energy change for H‐atom abstraction reaction ranges from ?37.8 to ?15.9 kcal/mol; for ? OH addition ranges from ?3.85 to ?1.23 kcal/mol; and for nucleophilic attack on the carbonyl group is 13.9 kcal/mol. The calculated rate constant between neutral ibuprofen and ? OH, 6.72 × 10⁹ M^?1s^?1, is consistent with the experimental value, 6.5 ± 0.2 × 10⁹ M^?1s^?1. Our results provide direct evidence for byproduct formation and identification on the molecular level. © 2013 Wiley Periodicals, Inc.     

1,n‐Hydrogen‐Atom Transfer (HAT) Reactions in Which n≠5: An Updated Inventory

Hydrogen‐atom transfer (HAT) counts amongst the most widely investigated routes to carbon‐centered radicals. Intramolecular processes involving 1,5‐HAT are widespread to promote regioselective radical “C?H activation”. The aim of this review is to draw up a comprehensive inventory of the less commonly encountered 1,n‐radical translocations (n≠5) with the aim to update this topic with the most recent relevant data.