Photochemistry and vibrational spectra of matrix-isolated 5-ethoxy-1-phenyl-1H-tetrazole

A combined matrix isolation FT-IR and theoretical DFT(B3LYP)/6-311++G(d,p) study of the molecular structure and photochemistry of 5-ethoxy-1-phenyl-1H-tetrazole (5EPT) was performed. A new method of synthesis of the compound is described. Calculations show three minima, very close in energy and separated by low-energy barriers (less than 4 kJ mol-1), in the ground-state potential energy profile of the molecule. The method of matrix isolation enabled the reduction of the number of populated conformational states in the experiment at low temperature due to the effect known as conformational cooling. As a result, the spectrum of the as-deposited matrix of 5EPT closely matches that of the most stable conformer predicted theoretically, pointing to the existence of only this conformer in the low-temperature matrixes. In this structure, the dihedral angle between the two rings, phenyl and tetrazole, is ca. 30 degrees, whereas the ethyl group stays nearly in the plane of the tetrazole ring and is as far as possible from the phenyl group. In situ UV irradiation (lambda > 235 nm) of the matrix-isolated 5EPT induced unimolecular decomposition, which led mainly to production of ethylcyanate and phenylazide, this later compound further reacting to yield, as final product, 1-aza-1,2,4,6-cycloheptatetraene. Anti-aromatic 3-ethoxy-1-phenyl-1H-diazirene was also observed experimentally as minor photoproduct, resulting from direct extrusion of molecular nitrogen from 5EPT. This species has not been described before and is now characterized by infrared spectroscopy for the first time.     

Density functional study and the vibrational spectra of 4-chloro-5-fluoro-1,2-phenylenediamine

The solid phase FTIR and FT-Raman spectra of 4-chloro-5-fluoro-1,2-phenylenediamine (C(6)H(6)ClFN(2)) have been recorded in the region 4000-400 and 3500-100 cm(-1), respectively. The spectra were interpreted with the aid of normal coordinate analysis following a full structure optimization and force field calculations based on the density functional theory (DFT) using the standard B3LYP/6-31G( *) method and basis set combination. A close agreement was achieved between the observed and calculated frequencies by refinement of the scale factors.     

Efficient synthesis of methyl 4-chloro-6-fluoro-3-formyl-2H-chromene-2-carboxylate and its derivatives

Abstract  

Methyl 4-chloro-6-fluoro-3-formyl-2H-chromene-2-carboxylate was synthesized conveniently using Vilsmeier reagent. A series of new 2H-chromenes was prepared in high yields by introducing a corresponding β-halovinylaldehyde into condensation and cyclization reactions with active methylene compounds.     

The vibrational spectra, assignments and ab initio/DFT analysis for 3-chloro, 4-chloro and 5-chloro-2-methylphenyl isocyanates

The Raman (3500-50 cm(-1)) and infrared (4000-200 cm(-1)) spectra of 3-chloro, 4-chloro and 5-chloro-2-methylphenyl isocyanates have been measured. Ab initio and density functional theory calculations, at the levels of RHF/6-311G* and B3LYP/6-311G*, have been performed: energies, optimized geometrical parameters, vibrational frequencies, infrared intensities, Raman activities, depolarization ratios and nuclear displacements are obtained. Potential energy distributions (PEDs) and normal modes, for the spectral data computed at B3LYP/6-311G*, have also been obtained from a force-field calculations. A complete vibrational assignments of the observed spectra have been proposed. The force-field calculations have shown that, several of the normal modes are coupled, as is the case with large molecular systems possessing very low or no symmetry, such as investigated in the present study. Further, the investigation of the internal rotation of the isocyanate, NCO, by B3LYP/6-31G* level of theory has shown that the moiety maintains nearly the same orientation in all the three compounds (approximately 140-145 degrees tilt to the para-position) as in phenyl isocyanate. Two conformers, cis and trans forms, with respect to the substituents, NCO and CH(3), have been determined: the cis form lies above trans form by less than a kilocalorie per mole for each compound.     

The vibrational spectra and rotational isomerism of methyl ethyl sulphone-d0, -d3 and -d5

The infrared and Raman spectra of methyl ethyl sulphone, methyl ethyl sulphone-1,1,1-d₃ and methyl ethyl sulphone- 1,1,1,3,3-d₅ have been presented with vibrational assignments. Two solid states have been identified in which the molecules are either the trans or the gauche rotational isomers: one solid, the A form, occurs in cooled KBr disks used for infrared spectra while the other was found in CsI disks under ambient conditions. A mixed crystal form has also been found. In the liquid state the enthalpy of the B rotational isomer is slightly less than that of the A isomer by 90 (± 140) J mol⁻¹     

Reactions of methyl 3-hydroxythiophene-2-carboxylate. Part 4. Synthesis of methyl 5-azolyl-3-hydroxythiophene-2-carboxylates

The indirect introduction of an azolyl group in position 5 of compound 1 by an easy two-step procedure taking place at room temperature is described. A similar procedure yields the 4-chloro derivatives of these 5-azolyl compounds. The same method is applied for the introduction of a 5-azido group and from the 5-azido compounds, 5-v-triazolyl derivatives are obtained by a known method.     

Insights into the bromination of 3-aryl-5-methyl-isoxazole-4-carboxylate: synthesis of 3-aryl-5-bromomethyl-isoxazole-4-carboxylate as precursor to 3-aryl-5-formyl-isoxazole-4-carboxylate

Results of the detailed investigations on the bromination of the methyl group of 3-aryl-5-methyl-isoxazole-4-carboxylate, a precursor to obtain 3-aryl-5-formyl-isoxazole-4-carboxylate, are described. The products generated during the study have been utilized as substrates for the synthesis of isoxazole-fused heterocycles.     

Molecular structure and vibrational spectra of 3-chloro-4-fluoro benzonitrile by ab initio HF and density functional method

In this work, the experimental and theoretical spectra of 3-chloro-4-fluoro benzonitrile (3C4FBN) were studied. The Fourier transform infrared and Fourier transform Raman spectra of 3C4FBN were recorded in the solid phase. The optimized geometry was calculated by HF and B3LYP methods with 6-311++G(d,p) basis set. The harmonic-vibrational frequencies, infrared intensities and Raman scattering activities of the title compound were performed at and HF/B3LYP/6-311++G(d,p) level of theories. The scaled theoretical wave number showed very good agreement with the experimental values. The thermodynamic functions of the title compound was also performed at HF/6-31G(d,p) and B3LYP/6-311++G(d,p) level of theories. A detailed interpretation of the infrared and Raman spectra of 3C4FBN was reported. The theoretical spectrograms for FT-IR and FT-Raman spectra of the title molecule have been constructed.     

Hydrogen bond, dimerization and vibrational modes in 2-chloro-3-hydroxybenzaldehyde and 3-chloro-4-hydroxybenzaldehyde from vibrational and ab initio studies

Ab initio conformers and dimers have been computed at RHF and B3LYP/6-31G* levels for isomers 2-chloro-3-hydroxybenzaldehyde and 3-chloro-4-hydroxybenzaldehyde to explain the observed infrared absorption and Raman vibrational spectral features in the region 3500-50 cm(-1). The position of the chlorine in ortho position with respect to aldehyde group in 2-chloro-3-hydroxybenzaldehyde yields four distinct conformers; whereas the chlorine in meta position in 3-chloro-4-hydroxybenzaldehyde yields effectively only three conformers. Major spectral features as strong absorptions near 3160-80 cm(-1), down-shifting of the aldehydic carbonyl stretching mode and up-shifting of hydroxyl group's in-plane bending mode are explained using ab initio evidence of O-H?O bond-aided dimerization between the most stable conformers of each molecule. Absorption width of about 700 cm(-1) (～8.28 kJ/mol) of O-H stretching modes suggests a strong hydrogen bonding with the ab initio bond lengths, O-H?O in the range of 2.873-2.832 ?. A strong Raman mode near 110-85 cm(-1) in each molecule is interpreted to be coupled vibrations of pseudo-dimeric trans and cis structures.     

Conformational behaviour and vibrational spectra of cyclopropyl methyl ketone and methyl cyclopropyl-carboxylate

Infrared spectra in the vapour, liquid, and crystalline states and Raman spectra in the liquid and crystalline states have been obtained for cyclopropyl methyl ketone and for methyl cyclopropylcarboxylate. In cyclopropyl methyl ketone, the dominant conformer in the liquid and vapour states, the cis, has been shown to exist exclusively in the crystal. In methyl cyclopropylcarboxylate, the conformer dominant in the liquid and vapour states has been demonstrated to exist in the crystal. Vibrational assignments are made for the ring modes and for those modes which are sensitive to conformational changes.     

Synthesis of methyl 2-oxo-5-vinyl-2,5-tetrahydrofuran-3-carboxylate

A synthesis of methyl 2-oxo-5-vinyl-tetrahydrofuran-3-carboxylate involving five synthetic steps from commercially available 3,4-dihydroxybutene is reported.     

Alkylation of methyl 4-chloro-3-oxobutanoate with di- and tribromoalkanes

Russian Journal of Organic Chemistry - Alkylation of methyl 4-chloro-3-oxobutanoate with 1,2-dibromoethane, 1,3-dibromopropane, and 1,2,3-tribromopropane afforded the corresponding dimethyl...     

5-甲基-4-[3-氯-4-(3-氟苄氧基)苯氨基]吡咯并三嗪-6-甲酸乙酯的合成及其抗肿瘤活性

以3-甲基-2-氰基吡咯-4-甲酸乙酯为原料,采用新的路线,经3步反应合成了5-甲基-4-[3-氯-4-(3-氟苄氧基)苯氨基]吡咯并[2,1-f][1,2,4]三嗪-6-甲酸乙酯。通过对其合成过程中的反应条件优化,使反应收率得以提高,三步反应总收率26.4%。借助核磁共振、质谱等检测手段对反应中间体和目标化合物进行了结构表征。通过对人系肿瘤细胞SW480、A549和A431生长抑制活性实验,表明所得目标化合物能够选择性抑制肿瘤细胞A431的增殖(IC50:2.62±1.82μM)。     

Conformations and vibrational spectra of 2-chloro-3-fluoro-1-propene and 2-bromo-3-fluoro-1-propene

The infrared spectra of 2-chloro-3-fluoro- and 2-bromo-3-fluoro-1-propene as vapours and liquids were recorded in the region 4000–4050 cm^?1. Additional spectra of the amorphous and crystalline solids at ?170 °C and of the liquids in polar and non-polar solvents were recorded between 4000 and 200 cm^?1.Raman spectra, including semi-quantitative polarization measurements of the liquids were obtained. Spectra were also recorded with the samples dissolved in polar and non-polar solvents, and unannealed as well as annealed crystalline solids were studied at ?180 °C.Approximately 14 vibrational bands present in the spectra of the liquids, solutions and the glassy solids vanished in the infrared and Raman spectra of the crystals. From various criteria it can be concluded with certainty that the more polar (gauche) and less polar (cis) conformers were present in the crystalline chloro- and bromo- compounds, respectively. From infrared and Raman band intensities it was estimated that the conformational equilibrium in chlorofluoro-propene was highly displaced towards cis in the vapour, with both conformers approximately equally abundant in the liquid state (30 °C). For bromofluoro- propene the equilibrium was still further displaced towards the cis conformer.A striking similarity between the spectra of the two compounds was ob- served. The fundamental frequencies have been tentatively assigned and checked by force constant calculations. Dipole moments and relative stabilities of the conformers were estimated by a CNDO calculation.     

Electronic and vibrational spectra of 2,4,6-trichloro- and 6-chloro-2,4-dimethoxypyrimidine

This paper presents the investigations of the electronic and vibrational spectra of 2,4,6-trichloropyrimidine and 6-chloro 2,4-dimethoxypyrimidine. The electronic spectra have been recorded in the liquid and vapour states in the region 50000-28000 cm⁻¹. Then-π and π-π transitions are classified in each case. Infrared absorption spectra of 2,4,6-trichloropyrimidine in nujol have been recorded in the region 4000-400 cm⁻¹. It is concluded that substituents like Cl or OCH₃ do not have much influence on thesp ² electron of the nitrogen atom of the ring. From infrared studies the mass-dependent modes and the modes insensitive to substitution have been pointed out. The assignments are tentative and are based on the group frequency approach and data available for similar molecules.