The new ONIOM (our own n-layered integrated molecular orbital and mechanics) approach has been proposed shown to be successful in reproducing benchmark calculations experimental results. ONIOM3, a three-layered version, divides system into an active part treated at very high level of ab initio theory like CCSD(T), semiactive that includes important electronic contributions is the HF or MP2 level, nonactive handled using force field approaches. scheme allows us study larger more accurately...

A new theoretical method, called IMOMO (integrated MO (molecular orbital)+MO), for integration of two different levels approximation is presented. Only the active or more difficult part a molecule treated at higher level and rest lower approximation. The integrated total energy derivatives are defined from three calculations, structure transition state as well equilibrium can be optimized using energy. Any combination any molecular orbital approximations (ab initio, density functional to...

The integrated MO+MO (IMOMO) method, recently proposed for geometry optimization, is tested accurate single point calculations. principle idea of the IMOMO method to reproduce results a high level MO calculation large ‘‘real’’ system by dividing it into small ‘‘model’’ and rest applying different levels theory two parts. Test examples are activation barrier SN2 reaction Cl−+alkyl chlorides, C=C double bond dissociation olefins energy epoxidation benzene. effects basis set in lower as well...

An original computational method of ab initio valence bond type is proposed, aiming at yielding accurate dissociation energy curves, while dealing with wave functions being very compact and clearly interpretable in terms Lewis structures. The basic principle that the function allowed to have different orbitals for Thus, throughout process, so-called ‘‘breathing orbitals’’ follow instantaneous charge fluctuations broken by undergoing changes size, hybridization, polarization. applied F2 FH....

An expedient synthesis of a new family configurationally stable dioxa[6]helicenes was established using sequential helicoselective organocatalyzed heteroannulation/eliminative aromatization via enantioenriched fused 2-nitro dihydrofurans featuring both central and helical chiralities. Starting from simple achiral precursors, broad range these previously unknown chiral heterocyclic scaffolds were obtained with good efficiency, their proceeded very high enantiopurity retention in most cases.

Enantioselective construction of small molecules displaying a configurationally stable helical shape built on fused-tetracyclic core is daunting synthetic challenge even more pronounced when five-membered rings are incorporated in the structure. The resulting higher configurational lability strongly hampers their access, and therefore development new efficient methodologies timely highly desirable. In this context, we describe padlocking approach

Abstract Diffusion coefficients of a broad range molecules with molecular weight ranging from 100 to 800 g/mol have been measured in polypropylene, by solid/solid contact methods (without liquid contact), at 40°C. The behaviors the different are compared those linear alkanes. diffusion correlated parameters describing size, shape, and flexibility molecules. concept weighted fractionated volume is introduced using modeling. It enables classification according modes molecule displacement...

A new and less expensive G2-type approach, G2MS, which can be used for accurate energy prediction up to seven eight atoms has been proposed tested against the standard G2 data set. The results compare well with other methods. G2MS method performs an extrapolation of correlation basis set effects, while integrated MO+MO (IMOMO) provides electronic steric effects from a small model large real system. Thus, using as high-level in IMOMO is natural approach predictions molecular systems. predicts...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNature of the Differential Electron Correlation in Three-Electron Bond Dissociations. Efficiency a Simple Two-Configuration Valence Method with Breathing OrbitalsPhilippe C. Hiberty, Stephane Humbel, and P. ArchirelCite this: J. Phys. Chem. 1994, 98, 45, 11697–11704Publication Date (Print):November 1, 1994Publication History Published online1 May 2002Published inissue 1 November...

Well-defined optically pure transition metal (TM) complexes bearing C1- and C2-symmetric N-heterocyclic carbene (NHC) ligands were prepared from prochiral NHC precursors. As predicted by DFT calculations, our strategy capitalizes on the formation of a metal-carbene bond which induces an axis chirality. Configurationally stable atropisomers various NHC-containing TM isolated preparative HPLC chiral stationary phase in good yields excellent optical purities (up to 99.5% ee). The transfer Cu...

Polycyclic molecules and tetrahydroquinoleines were obtained in a tandem reaction involving the diastereoselective addition of alpha-aminoalkyl radicals to (5R)-5-menthyloxy-2[5H]-furanone 1. The facial diastereoselectivity on 1 is >/=90%. produced from tertiary amines by photochemical-induced electron transfer. When N,N-dialkylanilines 19 used as starting amines, rearomatization step was involved important side reactions observed. A mechanistic study isotopic labeling amine indicated that...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTWhat Is Physically Wrong with the Description of Odd-Electron Bonding by Hartree-Fock Theory? A Simple Nonempirical RemedyPhilippe C. Hiberty, Stephane Humbel, David Danovich, and Sason ShaikCite this: J. Am. Chem. Soc. 1995, 117, 35, 9003–9011Publication Date (Print):September 1, 1995Publication History Published online1 May 2002Published inissue 1 September 1995https://doi.org/10.1021/ja00140a017RIGHTS & PERMISSIONSArticle...

Ammonium adducts of trimethylsilyl-terminated poly(dimethylsiloxane) (CH(3)-PDMS) produced by electrospray ionization were submitted to collision induced dissociation and revealed a particular MS/MS behavior: the same three main product ions at m/z 221, 295, 369 always generated in very similar relative abundances regardless size precursor ion. Combining accurate mass measurements ab initio calculation allowed stable cyclic geometries be obtained for these ionic species. Dissociation...

The configurational stability of chlorophosphines is investigated. Several mechanisms involving chlorophosphine monomer, dimers, and adducts with HCl are evaluated by density functional theory calculations. presence in the medium found to catalyze P-center chiral inversion at room temperature. reaction involves a two-step mechanism low transition states (10 kcal.mol-1) stabilized achiral intermediate (-2.6 kcal.mol-1). Further calculations experiments on halogen exchange HBr corroborate this...

A new approach to extract the coefficients and weights of Lewis structures from Hückel wave function is designed: Hückel-Lewis projection (HL-P). The are obtained by on overlapping structures. This straightforward alternative ab initio approaches detailed used typical cases, including acrolein, allyl radical, pyrrole-like systems, imidazolylidene. trust parameter defined shown as a guide retrieve most important emblematic examples butadiene benzene chosen illustrate use this parameter.

The role of cations in the fragmentation polymer nitroxide labile end groups, as often deplored matrix-assisted laser desorption/ionization, was investigated. A combination different spectroscopic techniques and theoretical calculations implemented to address mechanistic aspect end-group cleavage a nitroxide-terminated poly(ethylene oxide) macroinitiator agent upon activation mass spectrometry. When occurring during ionization process, homolytic C−ON bond group results release moiety...

A set of 16 chiral ruthenium complexes containing atropisomerically stable N-Heterocyclic Carbene (NHC) ligands was synthesized from prochiral NHC precursors. After a rapid screening in asymmetric ring-opening-cross metathesis (AROCM), the most effective atrop BIAN-NHC Ru-catalyst (up to 97 : 3 er) then converted Z-selective catechodithiolate complex. The latter proved be highly efficient AROCM exo-norbornenes affording valuable trans-cyclopentanes with excellent Z-selectivity (>98 %) and...

Short strong hydrogen bonds are modeled with two resonating bonding structures issued from a valence bond analysis. A formula giving the dissociation energy as function of difference in proton affinities (ΔPA) is demonstrated. This equation expanded Taylor series and compared to similar equations found literature. It that correlations either experimental data or derived Marcus can be justified by same arguments.

Abstract Indium triflate catalysed tandem allylation–intramolecular hydroalkoxylation was efficiently carried out by using 1 mol‐% of the catalyst under mild conditions to afford dihydrobenzopyran ring system (chroman‐type structure) in good yields. Kinetic, mechanistic and theoretical studies are also presented.

Abstract Interactions of gold(I) catalysts with alkenes and alkynes are analyzed. Neutral chlorido, cationic phosphine N‐heterocyclic carbene complexes studied. High‐level ab initio calculations performed to benchmark the accuracy popular DFT methods. Donation backdonation contributions in bond between gold fragment alkene/alkyne substrate discussed. These depend on nature fragment, but also substituents alkene/alkyne.

A recent valence bond scheme based on Lewis structures, the BOND (VBB) method (BOND: Breathing Orbitals Naturally Delocalized) (Linares, M.; Braida, B.; Humbel, S. J. Phys. Chem. 2006, 110, 2505-2509), is applied to explore nature of resonance in allyl systems. Whereas radical correctly described by between two traditional a third "long-bonded" structure, which apparently creates pi distant carbon atoms, appears plays an important role ions description. The similar vertical energy (VRE) for...

Palladium(II) acetate complexes with phosphinous acids such as tert-butyl(phenyl)phosphinous acid (PAPd) have been successfully applied in a new [2 + 1] cycloaddition reaction between norbornadiene (NBD) and phenylacetylene (PhCCH) to produce exo-phenylmethylidenecyclopropane the solution phase. In present study, collision-activated (CAR)/collision-induced dissociation (CID) mass spectral experiments were performed on cationic Pd(II) complex (Pd(OPPhtBu)2H ion, [a]+). These useful for...

High-level ab initio calculations were performed on a two-center three-electron (2c−3e) bond between formaldehyde and the radical cation of ammonia. The stability resulting complex is found to be 21.8 kcal/mol, only 2.2 kcal/mol higher than hydrogen bonded same species. Upon replacing by thioformaldehyde (H2CS), 2c−3e 20 more stable corresponding complex. imine group also studied via H2CNH system. This compound exhibits larger energy, 32.0 but this still 8.8 in energy first theoretical...

A method for expressing the wave function in terms of Lewis structures is proposed and tested on allyl cation. This computational scheme called valence bond BOND (VBB). The compact VBB gives consistent results with breathing orbital (BOVB) resonance energy cation (54 55 kcal/mol BOVB, respectively). optimization sigma orbitals, such a way they adapt to each structure, makes use effect. It shown that this "breathing" frame more efficient resonant hybrid than localized state, so 63 obtained at...