Overtone spectroscopy of sulfonic acid derivatives

Vapor-phase OH-stretching overtone spectra of methanesulfonic acid and trifluoromethanesulfonic acid were recorded in the Deltav(OH) = 4 and 5 regions using cavity ring-down spectroscopy. We compare these spectra to those of sulfuric acid to consider the effect on vibrational overtone spectra of replacing one of the OH groups with a more or less electronegative group. We complement our experimental work with anharmonic oscillator local mode calculations of the OH-stretching frequencies and intensities. The presence of a weak intramolecular interaction between the hydrogen atom of the OH group and the oxygen atom of the adjacent S=O group in methanesulfonic acid lowers its OH-stretching frequency from what would otherwise be predicted based on the electronegativity of the methyl group.     

Chlorination of some benzene derivatives by chlorine fluosulfate

Conclusions Exhaustive chlorination is observed when chlorine fluosulfate is reacted with 1,3,5-trichlorobenzene and nitrobenzene under mild conditions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1160–1161, May, 1982.     

Overtone spectroscopy of butanol

Overtone spectra of CH and OH stretching vibrations in normal, secondary and tertiary butanol have been studied. A large number of combination and overtone bands, along with the fundamentals have been measured and assigned in the three cases. These data have been used to obtain the vibrational frequency, anharmonicity constant and dissociation energy for the CH and OH stretch motions in the respective molecules. Effect of dilution on the OH fundamental frequency in n-butanol causes a blue shift.     

Overtone spectra of aniline derivatives

Overtone spectra of 2-ethylaniline, N-methylaniline, N-ethylaniline, N,N-dimethylaniline and N,N-diethylaniline have been studied in 2500-15000 cm(-1) region. Vibrational frequency and anharmonicity constants for aryl/alkyl C-H stretch and N-H stretch vibrations have been determined. The effect of substitution of C(2)H(5) group on the ortho position in the ring and CH(3)/C(2)H(5) at the positions of the H-atom in NH(2) group has been studied in these molecules. It is noted that the aryl C-H stretching frequency and the N-H stretching frequency is appreciably increased due to the replacement of H in NH(2) group by CH(3)/C(2)H(5). These experimental observations are well supported by theoretical calculations for charge density on N-atom using molecular orbital AM(1) method.     

Overtone spectroscopy of isobutane at cryogenic temperatures

The spectra of the fundamental and overtones of the C---H stretches of (CH₃)₃CH have been measured in liquid argon solutions at 90 K and for the pure liquid sample at 135 K. Absorptions in the visible were obtained with a low temperature cell and a resonant continuous wave laser technique with acoustic detection. Absorptions in the IR and near-IR were observed with a Fourier transform spectrophotometer. Comparison is made between the absorption bands in gas phase, liquid argon solution, and liquid phase isobutane. The spectra of isobutane in solution show improved resolution of the vibrational bands with respect to the room temperature gas phase bands and the pure liquid bands at 135 K. To interpret the experimental results, overtone transitions are described in terms of the local mode model. A harmonically coupled anharmonic oscillator (HCAO) model was used to determine the overtone energy levels and assign the absorption bands to vibrational transitions. Ab initio molecular orbital calculations of geometries and vibrational frequencies were also performed.     

Overtone surface vibrational spectroscopy of zeolite-encaged molecules

Overtone spectra of adsorbed molecules yield information complementary to that obtained from the fundamentals, (i) enabling to follow the formation and development of bands up to high coverages, (ii) facilitating the assignment of bands, (iii) giving indication to the processes governing the bandshape and (iv) in case of diatomics making feasible the determination of changes of the constants of intramolecular potential, and so of the dissociation energy. The practicability is demonstrated by diatomics adsorbed in Mg²⁺-exchanged zeolite A.     

Reaction mechanism for the complete heterogeneous catalytic oxidation of chlorine derivatives of benzene

The complete catalytic oxidation of benzene and its chlorine derivatives is shown to proceed via the formation of a -complex that is further transformed into phenolate, carboxylate, and carbonate surface compounds, which give rise through desorption to oxides of carbon.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, Nos. 5–6, pp. 464–468, September–December, 1992.     

The electronic origin of the dual fluorescence in donor-acceptor substituted benzene derivatives

The origin of the dual fluorescence of DMABN (dimethylaminobenzonitrile) and other benzene derivatives is explained by a charge transfer model based on the properties of the benzene anion radical. It is shown that, in general, three low-lying electronically excited states are expected for these molecules, two of which are of charge transfer (CT) character, whereas the third is a locally excited (LE) state. Dual fluorescence may arise from any two of these states, as each has a different geometry at which it attains a minimum. The Jahn-Teller induced distortion of the benzene anion radical ground state helps to classify the CT states as having quinoid (Q) and antiquinoid (AQ) forms. The intramolecular charge transfer (ICT) state is formed by the transfer of an electron from a covalently linked donor group to an anti-bonding orbital of the pi-electron system of benzene. The change in charge distribution of the molecule in the CT states leads to the most significant geometry change undergone by the molecule which is the distortion of the benzene ring to a Q or AQ structure. As the dipole moment is larger in the perpendicular geometry than in the planar one, this geometry is preferred in polar solvents, supporting the twisted intramolecular charge transfer (TICT) model. However, in many cases the planar conformation of CT excited states is lower in energy than that of the LE state, and dual fluorescence can be observed also from planar structures.     

Correlation of ESCA shifts and Hammett substituent constants in substituted benzene derivatives

ESCA shifts of substituted benzene derivatives are shown to correlate with Hammett σ constants. An explanation of this correlation is given in terms of the thermodynamic model for core electron binding energy shifts, and it is shown that ESCA shifts in benzene derivatives can be treated as a linear free energy relationship.     

The electronic spectra of the alkyl,fluorine and chlorine substituted derivatives of silane

The main characteristics of the ultraviolet absorption spectra of simple alkyl, fluorine and chlorine derivatives of silane are described. The interpretation of these spectra is discussed in relation to the respective photoelectron spectra, the Rydberg-valence-shell distinction and involvement of 3d atomic orbitals.Dedicated to Professor Dr. Hermann Hartmann on the occasion of his 65th birthday.     

Overtone spectroscopy of C-H ethyl stretches of 1-butyne

Room-temperature photoacoustic (PA) spectra and jet-cooled action spectra of the first to third overtone regions of the ethyl C-H stretches in vapor phase 1-butyne, CH3CH2C[Triple Bond]C-H, were measured. Both the PA and action spectra exhibit a complex multiple peak structure being better resolved and more pronounced in the latter, due to inhomogeneous structure reduction. The observed manifolds were analyzed in terms of a simplified joint local-/normal-mode (LM/NM) model accounting for two types of C-H stretches (methyl and methylene) and for Fermi resonances between stretches and deformations. The retrieved parameters, used for calculation of the eigenstates, come from the best-fit parameters based on the diagonalization of the vibrational Hamiltonian in the LM/NM basis. The parameters were obtained by comparing the eigenvalues and the sum of the squares of the expansion coefficients of the eigenvectors of the C-H stretches of methyl and methylene to the action spectra peak positions and intensities, respectively. This approximate model vibrational Hamiltonian is proposed to explain most observed spectral features, corresponding to C-H stretch bands and to combinations of C-H stretches and deformations, indicating the importance of the Fermi resonance. The model was also applied to calculate the dynamics of the C-H stretching modes resulting from coupling with the deformations, implying rapid initial state decay on subpicosecond time scale. Decays of several picoseconds were found for complete transfer of probability from the initially prepared state of methylene and methyl to the counterpart LM states.     

A substituted benzene ring synthesis

$\text{N}$-Aminopyrroles are used in a new, versatile and high yield substituted benzene ring synthesis.     

Spectroscopic calculations of CH bond dissociation energies for ethene, propene, and benzene chlorine derivatives

CH bond dissociation energies have been determined by spectroscopic and quantum-chemical calculations for ethane, propene, and benzene chlorine derivatives. The spectroscopic values of CH bond dissociation energies were obtained from the fundamental absorption bands in an anharmonic approximation using the variation method and the Morse harmonic basis. Quantum-chemical calculations were carried out using the 6-311G(3df,3pd)/B3LYP basis. The resulting tendencies of variation of bond dissociation energies are discussed in relation to changes in the structure of the molecule.     

Oxidation of substituted phenols with chlorine dioxide

Chlorine dioxide was used to oxidize sterically hindered phenols and their derivatives (2,6-di-tertbutylphenol, 2,6-diisobornylphenol, 2,6-di-tert-butyl-4-methylphenol, 2,6-diisobornyl-4-methylphenol, and 3,5-diisobornyl-4-hydroxybenzaldehyde) in organic solvent.     

Identification of some isomeric 3,5-unsymmetrically substituted 1-aroyl-pyrazole derivatives by NMR spectroscopy

The ¹H and ¹³C nmr chemical shifts are used for the structural assignment of isomeric 1-aroyl-4,5-dihydro-5-hydroxy-4,4-dimethyl-1H-pyrazoles 1 unsymmetrically substituted with phenyl or methyl in the 3,5-positions of the pyrazole ring. The ¹H nmr spectra of 1-aroyl- or 1-acetyl-4-methyl-1H-pyrazoles 2 are useful in structure elucidation of unsymmetrically 3- or 5-methyl substituted derivatives.     

Unconvential construction of a substituted benzene ring

A substituted biphenyl suitable for elaboration to the antibiotic resistomycin ($\text{1}$) has been synthesised by a novel double Michael process involving dimethyl β-oxoglutarate and the diacetylenic diester ($\text{4}$).     

Pentafluorophenyl derivatives of chlorine trifluoride

A reaction between C₆F₅Cl and elemental fluorine under pressure produced pentafluorophenylchlorine(III)difluoride⁽¹⁾ and 1,2-difluoro-1,2-bis(pentafluorophenyl)dichlorane, C₆F₅Cl(F)Cl(F)C₆F₅.The dichlorane was a stable colorless liquid with a boiling point of 121 – 123°. Its characterization by elemental analysis, IR, NMR and Mass Spectra will be presented. It is believed to be the first stable compound with a chlorine-chlorine bond and may be considered to be a derivative of the unknown Cl₂F₄.     

Relative energies of substituted benzene valence isomers

Ab initio calculations employing the STO-3G basis set are used to obtain the relative energies of the benzene valence isomers and some selected monosubstituted derivatives. We find that 3,3'-bicyclopropenyl, the least stable of the five (CH)₆ examined, is slightly more stable in the anti conformation than the gauche (Φ = 45°) conformation in agreement with experiment. Substituents are calculated to produce significant changes in the relative energies of the benzene valence isomers. The ground-state isomerization of 1-Dewar benzeneearbinyl cation to benzyl cation is more exothermic than the aromatization of Dewar benzene, but is, in contrast to the latter, symmetry-allowed.