Molecules-in-molecules calculations with fixed resonance integrals

A simple equation for the evaluation of resonance integrals from overlap integrals and ionization potentials of the molecular fragments is suggested for molecules-in-molecules π electron calculations. The singlet π → π* transition energies of some benzene derivatives containing donor substituents were calculated. The best results were obtained if in the expression of the resonance integral the first experimental ionization potential of the methyl derivative of the donor groups is used.     

Molecular-orbital calculations on some mesoionic compounds

Molecular-orbital calculations have been performed on sydnone, sydnone imine, ψ-oxatriazole, and isosydnone rings and their positive ionized forms by the Pariser–Parr–Pople–Brown–Heffernan method. The importance of elaborate open-shell calculations and the effect of introducing nonneighbor core resonance integrals in this order of approximation are investigated. The available experimental data on closely related compounds are qualitatively in agreement with the calculated values. The computed charges and bond orders demonstrate that certain structural features are common to all five-membered mesoionic ring systems and in agreement with recent experimental findings.     

Hydroxyalkylation of conjugated nitroalkenes with activated nonenolizable carbonyl compounds

[reaction: see text] The Morita-Baylis-Hillman reaction of a variety of conjugated nitroalkenes with activated nonenolizable carbonyl compounds such as glyoxylate, trifluoropyruvate, pyruvaldehyde, and ninhydrin in the presence of 40-100 mol % of DMAP in acetonitrile or 100 mol % of imidazole in CHCl(3) or THF provided the adducts in decent to good yields. In most cases, the reactions catalyzed by DMAP in acetonitrile were faster and provided the desired MBH adducts in higher yields as compared to the imidazole catalyzed reactions.     

Molecular mechanics calculations on carbonyl compounds. III. Cycloketones

Molecular mechanics (MM4) calculations were carried out on cycloketones for ring sizes ranging from 4 to 11 carbon atoms. The MM4 relative energies for the various conformations of the cycloketones were compared to density functional theory (DFT) calculations (B3LYP/6‐31G*), which were also carried out in this work. For small ring sizes (n=4–6), calculated molecular geometries, dipole moments, moments of inertia, and vibrational spectra were compared to experimental data. The axial–equatorial energy differences in methyl‐substituted cyclohexanones were also calculated by MM4 and compared to ab initio, DFT, and experimental results. The results of the MM4 studies on cycloketones showed significant improvement from those of MM3 calculations performed in parallel with the MM4 calculations. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1451–1475, 2001     

Regio- and stereoselectivity in the addition of metal n,n-dimethylphenylacetamide enolates to some conjugated carbonyl compounds

The nucleophilic addition of lithium, sodium, potassium and bromomagnesium N,N-dimethylphenylacetamide enolates to cinnamic aldehyde, chalcone and methyl cinnamate is studied. The regioselectivity of the reaction is found to depend on the metal counter ion and other reaction conditions. The stereoselectivity under kinetic and thermodynamic conditions does not depend on the metal. The reactivity of the amide-enolates is compared with the reactivity of other enolates already studied.     

The reactions of combined organocuprate-chlorotrimethylsilane reagents with conjugated carbonyl compounds

Organocuprates and chlorotrimethylsilane are compatible as separate species in THF or ether solution at ?50 to ?78°, and in combination can both accelerate and improve 1,4-addition reactions with conjugated carbonyl compounds.     

Molecular mechanics calculations on carbonyl compounds. IV. Heats of formation

Molecular mechanics (MM4) calculations on the heats of formation of aldehydes and ketones were carried out for a total of 59 compounds (10 aldehydes and 49 ketones). Optimization of the heat of formation parameters was obtained by a least squares fit to the experimentally known heats of formation. With the optimized MM4 heat of formation parameters, the MM4 calculated heats of formation showed significant improvement over those of MM3. The standard and weighted root mean square deviations for the MM4 values were 0.35 and 0.31 kcal mol^?1, respectively, whereas for the MM3 values they were 0.42 and 0.39 kcal mol^?1, respectively. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1476–1483, 2001     

Effect of hydration on polarographic reduction of some carbonyl compounds

Hydration and acid-base equilibria of the hydrated form govern the reduction and oxidation of numerous carbonyl compounds. Aliphatic and aromatic aldehydes are reduced in the free carbonyl form and oxidized as geminal diol anions. In haloacetaldehydes and haloacetones the C?X bond can be reductively cleaved both in the free carbonyl and in the hydrated form, oxidized form is again the geminal diol anion. Schemes (6), (7), (10), (11), (12) and (13) summarize the mechanism of the hydration and its relation to electrooxidation and reduction. Differential pulse of polarographic waves enabled measurement of heights of waves close to the initial or final rise of current and following the variations of their height with changes in activity of the solution.     

Preparation of some metal carbonyl cluster formyl compounds

The reduction of H₂Os₃(CO)₁₀S or HOs₃(CO)₁₀(O₂CMe) with KBH(OPr-i)₃ at low temperatures yields unstable formyl complexes which have been identified by ¹H NMR spectroscopy; at higher temperatures conversion into stable hydridoanions is observed.     

Quantum mechanical calculations on vibronic activity in the MCD spectra of carbonyl compounds

The magnetooptical properties (B terms) vibronically induced have been calculated for a series of carbonyl compounds in the region of the first absorption band. The rules deduced experimentally for the signs and sizes of the B terms induced by vibrations of different symmetry are generally confirmed by these calculations.     

The electronic structure of some heteroatom conjugated compounds

Molecular orbital calculations have been carried out on some heteroatom and heterocyclic conjugated compounds. Parameters have been chosen for the coulomb and resonance integrals which lead, in general, to the correctly predicted values of dipole moments, bond lengths and chemical reactivity. The exceptions are azides, oxamide and tetrazole derivatives, and the discrepancies are discussed.     

Condensation of salicylnitrile with some α-halo carbonyl compounds

3-Aminobenzofuran derivatives were obtained by condensation of salicylnitrile and 5-bromosalicylnitrile with -monochloroacetic acid derivatives and -halo ketones.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1171–1173, September, 1974.     

Reactions of cyclic sulfur ylides with some carbonyl compounds

The reaction of a six‐membered sulfonium ylide 5 with aldehydes or ketones afforded the oxirane derivatives 6a–d as a mixture of cis and trans isomers in excellent yields. In addition, the same reactions, using five‐ or six‐membered cyclic oxosulfonium ylides 7 and 11 , gave the corresponding oxirane derivatives in good yields. Moreover, the reaction of 11 with two equimolar amounts of base and 4‐hexen‐3‐one afforded the cyclooctene oxide derivative 16 with high stereoselectivity in 59% yield via a sequential Michael–Michael‐type addition of the ylide and the resulting enolate ion followed by an intramolecular Corey–Chaykovsky reaction. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:216–222, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10022     

Molecular mechanics calculations on carbonyl compounds. II. Open‐chain ketones

Open‐chain aliphatic ketones were studied with the molecular mechanics (MM4) force field. A total of seven compounds were examined. Structures were well fit, including moments of inertia. Rotational barriers, vibrational spectra, and dipole moments were also well fit. The overall root mean square errors for MM3 and MM4 were 0.27 and 0.18%, respectively, for the six moments of inertia (known experimentally for two compounds) and 31 and 20 cm^?1, respectively, for the vibrational frequencies (over 99 weighted modes). © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1426–1450, 2001     

Semi-empirical calculations of π-electron affinities for some conjugated organic molecules

Energy levels have been calculated for some conjugated systems containing C, N, and O atoms using a semi-empiricalmethod based upon a variableβ-γ modification of the Pariser-Parr-Pople approximation to the Hartree-Pock equation. Koopmans' theorem is used to relate the calculated energy of the lowest vacant molecular orbital, ?_LVMO, to the adiabatic electron affinity of a molecule. The approach is identical to that used previously by Kunii and Kuroda [13]. An excellent correlation is found between electron affinities deduced from recent beam experiments and ?_LVMO. This relationship is used to predict electron affinities for over 100 other organic molecules. In addition, excited state energies for negative ions are calculated, and good agreement is found with the available experimental data. Bound excited states are also predicted for some organics which contain the =C(CN)₂ substructure. The additive contribution of group substitutions to the electron affinity is discussed for the case of CN substitutions to ethylene, benzene, and naphthalene.