Is the neutral Knoevenagel reaction initiated by the carbanion formation?

The title reactions were studied by means of the density functional theory calculations. A base promoted reaction (called here ‘B’) was traced in a model composed of benzaldehyde, malononitrile, and (H₂O)₁₁. A neutral model (‘N’) of Ph‐CHO, H₂C(CN)₂ and (H₂O)₁₂ was also examined in line with a reported clean reaction. It was found that the ion pair of HC(CN) and H₃O⁺ is generated at the first step for N. For B, there are five elementary processes, and for N, four ones were obtained. By RB3LY/6‐311 + G** SCRF = PCM//RB3LYP/6‐31(+)G* energy calculations, the rate determining steps for both B and N reactions are the second proton removal, TS5(B) and TS3(N), respectively. In both B and N, the neutral species Ph(HO)HC‐CH(CN)₂ is the key intermediate. Copyright © 2010 John Wiley & Sons, Ltd.     

Structural analysis of certain linear operators representing chemical network systems via the existence and uniqueness theorems of spectral resolution. VI*

The present Part VI of this series of articles provides a mathematical and methodical link between (i) fundamental methodology in the repeat space theory (RST), which is referred to as the approach via the aspect of form and general topology and which has universal unifying power to handle additivity problems of molecules that have many identical moieties, and (ii) frontier electron theory of reactivity indices. Using theoretical tools required to link (i) and (ii), we establish a theorem from which the Generalized Alpha Existence Theorem (a theorem essential in the RST and proved in the previous Part V) directly follows. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 389–400, 2001     

Solid-state thiotropolone: an extremely rapid intramolecular proton transfer

Through variable-temperature solution-state NMR and molten- and solid-state CP/MAS (13)C NMR spectra, thiotropolone is found to exist as two rapidly equilibrated tautomeric structures, thione and enethiol, even in the solid state far below the melting point. The crystal structure shows an almost perpendicular packing, suggesting that the intramolecular hydrogen bond is dominant.     

An unsymmetrical behavior of reactant units in the Kolbe�CSchmitt reaction

Paths of the Kolbe?CSchmitt reaction were investigated by the use of RB3LYP/6-311(+)G(d,p) density functional theory calculations. In a monomer model composed of C₆H₅O^?, Na⁺ and CO₂ affording sodium salicylate [C₆H₄(OH)CO₂ ^?Na⁺], a proton-shift step (Z Naturforsch 57a:812, 2002) was found to have an unrealistically large activation energy. In consideration of the phenol volatilization in the Kolbe??s experiment and the need of the linearity of the proton-transfer path, a dimer model was constructed. Again, a mutual proton-transfer step has a large activation energy. Alternatively, in a dimer model, a transfer path where the phenoxide ion in one monomer acts as a proton acceptor was found to have a reasonable energy. Addition of one more sodium ion leads to the significant lowering of activation energies. Thus, in the dimer, two monomers behave differently (A?+?A????A?+?B); one is as if it were a catalyst.     

Structure of protonated thioformaldehyde

It is proposed, from an ab initio (4–31G) SCF calculation, that the most stable forms of protonated thioformaldehyde may be the C-protonated complexes H₃CS⁺. The energy-gradient technique was used for geometry optimization, and an energy decomposition analysis was carried out to elucidate the origin of this abnormal behavior of the C=S group.     

ESR studies of polyacenic semiconductive material

ESR measurements have been performed on the polyacenic material prepared by the pyrolytic treatment of phenol-formaldehyde resin. Six kinds of samples (A)-(F) with various electrical conductivity (σ) were employed for the measurements. Each sample shows a single narrow line, the g-values of which suggest the existence of unpaired electrons of π-type. If the sample (F) (σ = 1 × 10° S cm^?1) the single narrow line becomes drastically diminished in the presence of a small amount of oxygen.     

Cis-trans isomerization of iodine-doped polyacetylene

A quantitative analysis of the cis—trans isomerization of the lightly doped polyacetylene with iodine at room temperature is reported. The cis—trans ratio was determined on the basis of the infrared absorption measurement. The result clearly demonstrates the promotion of the isomerization with increase in the dopant concentration. The degree of the amount of the isomerization, however, is rather small compared with the previous study based on the nuclear magnetic resonance measurement.     

On the Hartree-Fock approximation to the electronic structure of molecule in the intense radiation field and the strong vibronic coupling

The Hartree-Fock approximation has been generalized to incorporate the nonadiabatic effect of molecular vibration previously by Tachibana et al. Here, we will derive the Hartree-Fock equation which reflects also the nonlinear effect of the infrared radiation field as well by using the Bloch-Nordsieck transformation which was discussed first by Nguyen-Dang and Bandrauk in the field of molecular physics. The Hartree-Fock equation reflects the non-adiabatic coupling between an electron and a molecular vibration and between the electron and a infrared radiation fields. The infrared radiation field also affects the dynamics of nuclear motion.Dedicated to Professor J. Koutecký on the occasion of his 65th birthday     

The electronic structures of cis-polyacetylene

The electronic structures of two possible forms of the so-called $\text{cis}$-skeletal polyacetylene ($\text{cis}$-polyacetylene) are investigated on the basis of the tight-binding LCAO-SCF-MO method under the CNDO/2 version. The analyses of the total energies per unit cell, the π bond orders and the interatomic interaction energies as to the both forms predict the $\text{cis}$-transoid backbone for the $\text{cis}$-polyacetylene. The examination of the patterns of particular molecular orbitals of the hypothetical $\text{cis}$-polymer with equal C-C bond lengths also supports the $\text{cis}$-transoid form.