IRAS ID Research Articles

Conformation, ordering and mobility of macromolecules in aromatic polyesters as studied by IR and solid‐state NMR spectroscopy

AbstractThermotropic main‐chain LC polyesters have been studied with the aid of IR and NMR spectroscopy. Rigid mesogens and mesogens with a possibility of conformational isomerism were examined. The dependence of the order parameters of the mesogens and spacers on the chemical structure of the polymer has been determined. The IR spectroscopy data and the data of the calculation of the possible conformations of the mesogen and the spacer confirm the theoretical predictions about the straightening of macromolecules in the anisotropic melt. Solid‐state 2H NMR spectra show that p‐oxybenzoic rings adjacent to a flexible spacer are more mobile than inner terphthalic rings. In decamethylene spacer the contrary holds true: the mobility of inner methylene groups is more marked than that of the α‐methylene groups bound to the mesogen.

Synthesis and reactivity of metal-containing monomers. 20. Photochemical structurization of gelatin mixtures with the participation of transition metal acrylates

The structurization activity of cobalt, nickel, and copper acrylates in gelatin layers under the influence of monochromatic laser radiation with a wavelength of 633 nm has been studied. It has been established with the aid of IR and electronic spectroscopy that the complexation of the acrylate salts of Co(II), Ni(II), and Cu(II) with gelatin is accomplished by means of the OH groups of the hydroxyproline residues. It has been shown that the photosensitivity and density of the photographic layers are determined by the nature of the transition metal and increase along the series Co(II) < Ni(II) < Cu(II). Thin phase holograms with a diffraction efficiency (η) equal to 33% have been obtained.

Azide-tetrazole tautomerism of diazidodiazines and their benzo analogs

It has been discovered with the aid of IR and NMR spectroscopy that 5-azidotetrazolo [1,5-a]quinazoline exists in solutions in a tautomeric equilibrium with ditetrazolo [1,5-a:1′,5′-c]quinazoline, and the thermodynamic and kinetic characteristics of the equilibrium have been determined. Azide-tetrazole tautomerism is not observed under these conditions for ditetrazolo[1,5-a:5′,1′-c]pyrazine, 6-azidotetrazolo [1,5-b]pyridazine, and their benzo analogs.

Polymerization of Acetylene with New Catalytic Systems and Optimization of the Properties of the Polymers

Abstract This paper reports a comparative study of different catalytic systems for the synthesis of novel polyacetylene films. That the morphology could be optimized by the use of a highly viscous complexing solvent together with thermal treatment [1,2] encouraged us to study the catalytic systems with the aid of ESR spectroscopy. The different samples were characterized with the aid of IR and ESR spectroscopic methods, conductivity measurements, and scanning electron microscopy before and after doping.

ChemInform Abstract: Oxidative Addition of Iodomethane to Acetylacetonatocarbonylphosphinerhodium(I) Complexes.

AbstractThe kinetics and mechanism of the title reaction (phosphine PR3 (R: ‐p‐chlorphenyl, ‐Ph, ‐p‐methoxyphenyl)) are studied with the aid of IR and visible spectrophotometry in 1,2‐dichloroethane.

The oxidative addition of iodomethane to acetylacetonatocarbonylphosphinerhodium(I) complexes

The kinetics and mechanism of the oxidative addition of CH 3I to [Rh(acac)(CO)(PX 3)], where X = p-chlorophenyl, phenyl and p-methoxyphenyl, were studied with the aid of IR and visible spectrophotometry in 1,2-dichloroethane. The reaction proceeds through an initial ionic intermediate followed by two consecutive equilibrium steps, the first involving acetyl formation followed by acyl → alkyl rearrangement to give [Rh(acac)(CO)(CH 3)- (I)(PX 3)] as final product. Equilibrium and rate constants are correlated with phosphine basicity.

Nature of the transformations of oleanolic acid in an acid medium

3-Trifluoroacetoxyoleanolic acid and 3-trifluoroacetoxyolean-13(18)-en-28-oic acid have been isolated from the mixture of the products of the transformation of oleanolic acid in a trifluoroacetic acid medium, and their structures have been established with the aid of IR, PMR and mass spectra. The formation of these products indicates an unambiguous route of the stabilization of the intermediate carbocation with the charge on the C-13 atom. The hydroxy group at C-3 is esterified by the trifluoroacetic acid.

Condensed imidazo-1,2,4-azines. 12. Synthesis and structure of substituted 5-H-imidazo[1,2-b]-1,2,4-triazepin-4-ones (-thiones)

The synthesis has been effected of new representatives of the imidazo[1,2-b]-1,2,4-triazepin-4-ones (-thiones). It has been shown with the aid of IR and UV spectroscopic and mass spectrometric methods that the lactam (thione) form is the predominant one for the compounds synthesized.

A spectral study of transition-metal complexes on a chelating ion-exchange resin containing aminophosphonic acid groups

The coordination mode of a commercial chelating ion-exchange resin, ES 467, containing aminomethylphosphonic acid groups anchored on a macroporous styrenedivinylbenzene copolymer, with several metal ions, such as chromium(III), cobalt(II), nickel(II), copper(II) and zinc(II) has been studied with the aid of IR, ligand field and ESR spectra. The chelating group of ES 467, aminomethylphosphonic acid, appears to bind different metal ions mainly through oxygen atoms of the phosphonic acid group, though, in the case of those species containing low-loading of metal ions, the secondary amine nitrogen atom also appears to take part in coordination. Most of the metal ions studied seem to be present as six-coordinated species in the polymeric matrix, whereas cobalt(II) species show electronic spectra which are consistent with the presence of both four-coordinated (tetrahedral) and six-coordinated (octahedral) structures of these species. The distribution coefficients for cobalt(II), nickel(II), copper(II) and zinc(II) have been determined and it appears that the resin ES 467 binds copper(II) ions selectively. An attempt has been made to find a possible relationship between the selectivity of the chelating resin and the stereochemistry of the adsorbed metal ions.

PHOTOOXIDATION OF 8‐METHOXYPSORALEN WITH SINGLET OXYGEN*

Abstract— The in vitro photooxidation of 8‐methoxypsoralen (8‐MOP) with singlet oxygen is studied. Irradiation of 8‐MOP(295–400 or320–400 nm) in the presence of oxygen for 72 h results in the formation of a product (1.4%) which is identified as 6‐formyl‐7‐hydroxy‐8‐methoxycoumarin by aid of IR, NMR, MS and co‐chromatography with an authentic sample. A study of this reaction in the presence of l,4‐diazobicyclo(2,2,2)octane, a singlet oxygen scavenger, indicates the involvement of 1O2 in the formation of this compound. In addition to this, formation of a novel dimer of 8‐MOP is reported.

Structure of trisphaeridine

The structure of the alkaloid trisphaeridine has been established with the aid of IR and UV spectroscopy, high-resolution mass spectroscopy, and PMR and13C NMR spectroscopy.

Norbornadiene complexes of transition metals : II. Stereochemistry of {2-(α-hydroxyethyl)norbornadiene} cyclopentadienylrhodium complexes

The interaction of Rh(CO) 2(acac) with diastereomeric 2-(α-hydroxyethyl)norbornadienes affords a racemic mixture of the diastereomeric Rh {η 4-C 7-H 7CH(OH)Me} (acac) (I), from which the individual isomers Ia and Ib are isolated by fractional crystallization. The ψ- exo (IIa) and ψ- endo (IIb) carbinols Rh {η 4-C 7H 7CH(OH)Me}(η 5-C 5H 5) are derived by substituting acetylacetonate ligand in Ia and Ib for cyclopentadienyl by the action of TlC 5H 5. Carbinol IIb is also obtained as the only product in the stereoselective reaction of aldehyde Rh(η 4-C 7H 7CHO)(η 5-C 5H 5) wiht methyllithium. The study of the stereochemistry of the removal of a hydroxy group from carbinols IIa and IIb, to form the cationic syn (IVa) and anti (IVb) η 3-allylic complexes [Rh(η 5-C 7H 7CHMe)(η 5-C 5H 5)] +PF 6 −, respectively, enables one to reliably assign their configuration. An estimation of the preferred conformation of diastereomers IIa and IIb with the aid of IR and 1H NMR data, as well as of other physical characteristics of the individual carbinols, has been made.

Linear-chain ferromagnetism in the one-dimensional compounds CoCl 2(pyrazole) 2 and CoCl 2(indazole) 2

Two linear-chain compounds of formula CoCl 2L 2, with L = pyrazole (pz) and indazole (indz), have been investigated with the aid of IR, far-IR, ligand field and ESR spectra. Magnetic susceptibility data have been collected in the temperature region 4.2–80 K. Analysis of the susceptibility data in terms of the Ising model yielded the values of the ferromagnetic intrachain exchange constants J = 7.2(6) and 7.4(9) cm -1 for the pz and indz compound, with corresponding g-values of g∥ = 7.9(7), g⊥ = 4.6(9) and g∥ = 10.8(9), g⊥ = 3(1), respectively. The results are discussed and compared with the similar compound CoCl 2(pyridine) 2. The influence of the bridge geometry and of the π-bonding properties of the organic ligands on the exchange constant are considered for the explanation of different J-values. It is suggested that the π-bonding properties of the organic ligand influence the magnitude of the superexchange constant to a great extent.

ChemInform Abstract: INTRAMOLECULAR DISPROPORTIONATION OF UNSATURATED ETHERS

We examined the possibility of the disproportionation of ethers on an aluminum--rhenium catalyst promoted by tetraalkylstannanes in a static system in the liquid phase with stirring at 20~ The products were analyzed chromatographically, as well as with the aid of IR, NMR, and mass spectrometry. It was found that the disproportionation of vinyl butyl and allyl butyl ether does not take place. However, the intramolecular disproportionation of diallyl ether (1) and the allyl ether of allylcarbinol (2) takes place with a high rate and a selectivity of ~i00% to form ethylene, 2,5-dihydrofuran, and 2,3-dihydro-u-pyran, respectively:

Intramolecular disproportionation of unsaturated ethers

We examined the possibility of the disproportionation of ethers on an aluminum--rhenium catalyst promoted by tetraalkylstannanes in a static system in the liquid phase with stirring at 20~ The products were analyzed chromatographically, as well as with the aid of IR, NMR, and mass spectrometry. It was found that the disproportionation of vinyl butyl and allyl butyl ether does not take place. However, the intramolecular disproportionation of diallyl ether (1) and the allyl ether of allylcarbinol (2) takes place with a high rate and a selectivity of ~i00% to form ethylene, 2,5-dihydrofuran, and 2,3-dihydro-u-pyran, respectively:

Isolation and identification of oxidation product of 2,6‐Di‐(tert‐butyl)‐4‐methylphenol from polyethylene film

Abstract2,6‐Di‐(tert‐butyl)‐4‐methylphenol is a widely used antioxidant in the production of polyethylene. An oxidation product of this antioxidant was isolated from aged polyethylene film and purified by preparative thin layer chromatography. This compound was identified as 3,3′, 5,5′‐tetra‐bis(tert‐butyl)‐stilbenequinone with the aid of IR‐ and mass spectroscopy. The generation of this oxidation product can lead to the discoloration of polyethylene film, and its formation can be catalyzed by contact with carbon black.

Isolation and identification oftrans‐3,5‐dimethoxystilbene from high quality tall oil fatty acids by liquid chromatography and mass spectrometry

Abstracttrans‐3,5‐Dimethoxystilbene has been isolated from high quality tall oil fatty acids (unsaponifiables 1.5% maximum, rosin acids 1.5% maximum), using liquid column chromatography and low temperature solvent fractional crystallization. The structure of this compound was determined with the aid of IR, mass and NMR spectrometry. Thetrans‐3,5‐dimethyoxystilbene was found to be responsible for the development of a red color during the epoxidation of the tall oil fatty acids.

Copolymerization of carbon dioxide and epoxide with organometallic compounds

AbstractAttempts to copolymerize carbon dioxide with epoxide led us to the first success in using carbon dioxide as a direct starting material for synthesizing high polymers. Some organometallic catalyst systems were found to catalyze the alternate copolymerization of carbon dioxide and epoxide, resulting in the formation of polycarbonates, the structures of which were confirmed with the aid of IR, NMR and elemental analysis. Diethylzinc‐water system produced a methanol insoluble aliphatic polycarbonate of much higher molecular weight than that produced by polycondensation. Thermal properties of the methanol insoluble polycarbonate were studied by differential thermal analysis and thermogravimetric analysis.

The structure of the product of oxidation of pyrrole C 8H 10N 2O

From the experimental results and with the aid of IR, UV and NMR techniques it is shown that structure of 5-(2-pyrrolyl)-2-pyrrolidinone (III) must be attributed to the product of oxidation of pyrrole, commonly known as oxo-bipyrrole (I, II).