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41.
Zusammenfassung Es wird für den Fall von zum gleichen Endprodukt führenden Parallelwegen der schließliche Endzustand erörtert; dieser ist notwendig der thermodynamische Gleichgewichtszustand zwischen sämtlichen Reaktionskomponenten; ein thermodynamisches Paradoxon existiert nicht.Mit 1 Abbildung. 相似文献
42.
A. Zaidi S. Lahmar Z. Ben Lakhdar P. Rosmus M. Hochlaf 《Theoretical chemistry accounts》2005,114(4-5):341-349
For the most stable linear isomer of C3S in its X1Σ+ state a six-dimensional potential energy surface (PES) has been calculated ab initio by coupled cluster – connected triples
(CCSD(T)) method. The analytic form of the PES has been transformed in a quartic force field in dimensionless normal coordinates
and employed in calculations of spectroscopic constants using second-order perturbation theory. The PES and the full kinetic
energy operator in internal coordinates have been used to calculate variationally the anharmonic ro-vibrational energies for
J=0 and J=1. The two experimental band origins of C3S observed in the gas phase, ν1 and ν1+ν5−ν5, agree very well with the theoretical values. The anharmonic ro-vibrational levels, including the bending modes up to 2200
cm−1, are reported. The singlet ground state PES has a saddle point at about 1.25 eV above the linear minimum and two other higher
lying cyclic local minima. The only dipole- and spin-allowed electronic transition between 0 and 5 eV is calculated to be
the 1Π−X1Σ+ transition with a vertical transition energy of 353.2 nm in good agreement with the matrix value of 378 nm. The dissociative
paths C + C2S, C2 + CS and C3 + S of low lying singlet and triplet states have been investigated.
Electronic Supplementary Material: Supplementary material is available in the online version of this article at dx.doi.org/10.1007/s00214-005-0683-7
Dedicated to Professor H. Stoll. 相似文献
43.
Dr. J. Oscar C. Jiménez‐Halla Dr. Marcin Kalek Prof. Jacek Stawinski Prof. Fahmi Himo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(39):12424-12436
The mechanism and sources of selectivity in the palladium‐catalyzed propargylic substitution reaction that involves phosphorus nucleophiles, and which yields predominantly allenylphosphonates and related compounds, have been studied computationally by means of density functional theory. Full free‐energy profiles are computed for both H‐phosphonate and H‐phosphonothioate substrates. The calculations show that the special behavior of H‐phosphonates among other heteroatom nucleophiles is indeed reflected in higher energy barriers for the attack on the central carbon atom of the allenyl/propargyl ligand relative to the ligand‐exchange pathway, which leads to the experimentally observed products. It is argued that, to explain the preference of allenyl‐ versus propargyl‐phosphonate/phosphonothioate formation in reactions that involve H‐phosphonates and H‐phosphonothioates, analysis of the complete free‐energy surfaces is necessary, because the product ratio is determined by different transition states in the respective branches of the catalytic cycle. In addition, these transition states change in going from a H‐phosphonate to a H‐phosphonothioate nucleophile. 相似文献
44.
Multiconfiguration self-consistent field and multiconfiguration reference interaction including the Davidson’s correction techniques were employed to calculate the potential energy curves (PECs) of the BeS/BeS+ electronic states correlating to the 4/5 lowest dissociation limits. After nuclear motion treatment, we deduced reliable spectroscopic data for the neutral and cationic bound states. For BeS, the transition moments and spin-orbit couplings were also evaluated and used later with the PECs to deduce the rovibronic transition probabilities and the radiative lifetimes in the low-lying states, and to investigate the unimolecular decomposition processes of BeS (X1Σ+, A1Π, 3Σ+ and B1Σ+) leading to Be(1Sg) + S(3Pg). The prominent mechanism is a spin-orbit induced predissociation via the repulsive BeS(13Σ−) state. Finally, we give the single ionization spectrum of BeS (X1Σ+) populating the BeS+ (X2Π, 12Σ−, 12Σ+, 12Δ, 22Σ+, 22Π and 32Π) electronic states. The adiabatic ionisation energy of BeS is estimated to be ∼9.15 eV. 相似文献
45.
46.
Andreas Stoy Julian Böhnke Prof. Dr. J. Oscar C. Jiménez‐Halla Dr. Rian D. Dewhurst Torsten Thiess Prof. Dr. Holger Braunschweig 《Angewandte Chemie (International ed. in English)》2018,57(20):5947-5951
The room‐temperature, ambient‐pressure reactions of CO2 with two species containing boron–boron multiple bonds led to the incorporation of either one or two CO2 molecules. The structural characterization of a thermally unstable intermediate in one case indicates that an initial [2+2] cycloaddition is the key step in the reaction mechanism. 相似文献
47.
48.
Frontispiece: Platinum Complexes Containing Pyramidalized Germanium and Tin Dihalide Ligands Bound through σ,σ ME Multiple Bonds 下载免费PDF全文
49.
Prof. Dr. Holger Braunschweig Dr. K. Geetharani Dr. J. Oscar C. Jimenez‐Halla Marius Schäfer 《Angewandte Chemie (International ed. in English)》2014,53(13):3500-3504
A new catalytic synthetic route to functionalized 1,2‐azaborinines has been developed by the [2+2]/[2+4] cycloaddition reactions of di‐tert‐butyliminoboranes and alkynes in presence of a rhodium catalyst. The first examples of ferrocene‐functionalized azaborinines have been synthesized using this strategy. Moreover, the regioselectivity of this reaction can be controlled by the formation of an intermediate rhodium 1,2‐azaborete complex, which results in the isolation of the first azaborinine boronic ester. The isolation of an NH‐containing BN isostere by elimination of isobutene from an N(tBu) group under thermolytic conditions has also been achieved. Theoretical studies give further insight into the formation of 1,2‐azaborinines and the elimination of isobutene from the N(tBu) group. 相似文献
50.
Ohne Zusammenfassung 相似文献