Thermal decomposition of copolymers of styrene and halogenated monomers

Copolymers of 1,2,2,2-tetrachloroethyl esters of unsaturated acids and halogenated N-phenyl maleimides with styrene were pyrolyzed; volatile products were analyzed with a mass spectrometer combined with a gas chromatograph. Hydrogen halide and carbon dioxide in the volatile products were determined during the thermal decomposition of copolymers in glass ampoules; the acyl chloride groups were determined in the residues. The thermal decomposition of copolymers of tetrachloroethyl esters with styrene sets in at ca. 230° by the release of chloral from the copolymer and splitting of some of the CCl bonds in the copolymer. The decomposition of copolymers of styrene with halogenated N-phenyl maleimides starts above 300° by depolymerization of the polystyrene chain sections and by splitting of some of the carbon-halogen bonds. At 310 and 500° for copolymers of tetrachloroethyl esters and at 500° for halogenated N-phenyl maleimides, there is radical dehydrohalogenation of the copolymers, with depolymerization of polystyrene blocks and splitting of carbon-carbon bonds in the main chain.     

A viscometric study of poly(methyl methacrylate) in 2-alkoxyethanols

θ-Conditions, the temperature coefficient of unperturbed dimensions of the macromolecules and the thermodynamic interaction parameters ψ and κ were determined for solutions of poly(methyl methacrylate) in 2-alkoxyethanols (methoxy, ethoxy and butoxy). The results for this series of solvents fit the data reported for other solvents and dln $\text{r}{}_0{}^2\text{/}\text{d}\text{T = 2.6 × 10}{}^{\mathrm{?3}}\text{K}{}^{\mathrm{?1}}$. The dependence of parameters ψ and κ exhibited deviations from the theoretical dependence, mainly near the limiting value ψ = 0.5.     

A field theoretical approach to calculate electronic Born-Oppenheimer coupling terms

In this paper we suggest to consider the spatial distribution of the Born-Oppenheimer nonadiabatic coupling terms as fields which are created by sources, located at degeneracy points, and which can be derived using the ordinary mathematical tools of field theory. It is shown that the curl-divergence equations as formed within a given Hilbert space [M. Baer, Chem. Phys. Lett. 35, 112 (1975)] can be converted into a set of inhomogeneous coupled Poisson equations which are solved for a given set of boundary conditions. The method is applied to the three-state Hilbert subspace of the H(3) system. The numerical results are compared with ab initio calculations for which a very encouraging fit is found.     

On distribution of molecular weight in anionic polymerizates of caprolactam

Measurement has been made of the dependence of the molecular weight distribution on the ratio of the catalytic system components and on the polymerization time for polycaprolactam obtained by anionic polymerization. A bimodal character of the curves was observed for products made using molar ratios of activator (N-benzoylcaprolactam) to initiator (sodium dihydro-bis(methoxyethoxy)aluminate) of 1:1 and 1:3, when the polymerization times were less than 1 hr. This course is explained by the influence of fast side-reactions, mainly condensations. For a ratio of 3:1 of the components of the catalytic system, smooth integral distribution curves are obtained, accounting for a very fast decrease in the strong base concentration in the initial stages of the polymerization.     

A gas electron diffraction and ab initio quantum-mechanical investigation into the molecular structure of tricyclo-(3.1.002,4)-hexane

The structure of tricyclo-(3.1.00^2,4)exane has been determined by gas phase electron diffraction. The molecule has an inversion centre. The mean carbon—carbon bond length, averaged over both three- and four-membered rings is 1.508 A. A model with equal C-C bond lengths fits to the measured diffraction intensities. The four-membered ring is planar with valency angles of 90°, while the carbon atoms of the three-membered rings form isosceles triangles. Ab initio quantum mechanical calculations at the STO-3G level support this geometry. The valency angle CCC (between three- and four-membered rings) for the equilateral four-membered ring model has been found experimentally to be 109.9°. The average C-H bond distance (1.080 Å) is small as a result of increased s-character in these bonds in agreement with reported INDO—LMO calculations.     

Obtention de selenopysultones lors de l'oxydation de thio-1 chromenes par le dioxyde de selenium

Selenium dioxide oxidation of 1-thiochromene leads to 3-formyl (5,6)benzo-1,2 thiaseleninne-1,1-dioxide, which is a representative of a hitherto unknown class of heterocyclic compounds. Pyrolysis of this compound leads to 2-formyl benzo(b)selenophen, by loss of sulphur dioxide. The reaction can be applied to other 1 thiochromenes but no similar behaviour has been observed for their selenium isologues.     

Application of capillary zone electrophoresis and reversed-phase high-performance liquid chromatography in the biopharmaceutical industry for the quantitative analysis of the monosaccharides released from a highly glycosylated therapeutic protein

Two assays for the quantitative determination of the neutral and amino-monosaccharides attached to a therapeutic glycoprotein were developed using capillary zone electrophoresis (CZE) and RP-HPLC. These assays meet the strict batch release requirements of the quality control in biopharmaceutical industry. The monosaccharides were released from the glycoprotein by hydrolysis with 2N trifluoroacetic acid. In the CZE assay the monosaccharides were reacetylated prior to derivatization with 8-aminopyrenesulfonic acid (APTS), reacetylation in the glycoprotein matrix was investigated in detail. The RP-HPLC method used pre-column derivatization with anthranilic acid in methanol-acetate-borate reaction medium; reacetylation was not necessary. However, epimerization of the different monosaccharides was observed and studied in detail. For the quantitative assay, separation of the amino-monosaccharide epimers had to be developed. The HPLC assay was validated.     

Spectral and electrochemical study of coordination molecules Cu4OX6L4: 3-Methylpyridine and 4-Methylpyridine Cu4OBrnCl(6−n)L4 complexes

The tetranuclear Cu₄OBr_nCl_(6-n)L₄ complexes, where L = 3-methylpyridine (3-Mepy), 4-methylpyridine (4-Mepy) and n=0–6 with trigonal bipyramidal coordination of copper(II) were prepared and their infrared and electronic absorption spectra as well as cyclic voltammograms in nitromethane solutions were measured. The polyhedra in Cu₄OBr_nCl_(6−n) (3-Mepy)₄ molecules are less distorted comparing with those of 4-Mepy analogues as indicated by infrared Cu₄O absorptions, far infrared Cu—Br, Cu—Cl, and Cu—N absorptions, d—d bands in electronic spectra and potentials, measured by cyclic voltammetry. The 3-Mepy complexes exhibit strong single infrared Cu₄O absorptions, while for related 4-Mepy complexes doubly split Cu₄O bands were observed. Two strongly overlapped d—d bands in electronic absorption spectra of the 3-and 4-Mepy complexes in nitromethane were resolved by Gaussian fitting. The 4-Mepy ligand produces slightly stronger ligand field than its 3-Mepy analogue. The maxima of high-energy d—d bands are in a linear correlation with the number of bromide ligands. The correlations for corresponding low-energy bands are considerably deviated from linearity. The halfwave potentials of the complexes in nitromethane correlate with both the number of bromides and the data of electronic absorption spectra suggesting that the reducing electron at the electrode process enters the half-filled d _{z 2} orbital of the copper(II) atom. The origin of a difference between the 3-and 4-Mepy complexes in their spectral and electrochemical properties is also discussed.     

Oxidative addition of some geminal halonitroalkanes to iridium(I) and platinum(0) compounds

Oxidative addition of 1-chloro-1-nitroethane to trans-IrCl(CO)-[P(CH₃)₂C₆H₅]₂ followed by treatment of the initial product with pyridine yields a new iridium(III) complex IrCl(py)[COC(NO₂)CH₃][P(CH₃)₂C₆H₅]₂, whose structure has been confirmed by X-rays crystallography. Two intermediate products have been observed by NMR spectroscopy; their structures have been tentatively assigned. The reaction of the corresponding bromine derivatives yields two isomers of the composition IrBr₂(CO)[CH(NO₂)CH₃][P(CH₃)₂C₆H₅]₂, and these are not affected by pyridine. The reaction of 1-chloro-1-nitroethane with Pt[P(C₆H₅)₃]₄ takes a completely different course in that yields nitrorethane and cis-PtCl₂[P(C₆H₅)₃]₂ as the main products, with no detectable formation of the products of oxidation addition. A brief mechanistic investigation points towards the participation of radicals and radical anions as transient intermediates and a mechanism is proposed which explains most of the experimental results.     

Influence of the pyridine methyl substituent position on the chemical changes of the NCS groups in the thermal decomposition of coordination compounds of the type Cu(NCS)2L2

The influence of the position of the CH₃ group in picoline and lutidine ligands on the degree of chemical change of the NCS groups in coordination compounds of the type Cu(NCS)₂L₂ (whereL=2-, 3- and 4-picoline, and 2,3-, 2,4-, 2,5-, 2,6-, 3,4- and 3,5-lutidine) is dealt with. The most marked effect of the CH₃ group is found to be exerted in position 4. This effect of the methyl group on the degree of chemical change points to the mutual influence of the ligands in coordination compounds of Cu(II).

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Zusammenfassung Der Artikel befaßt sich mit dem Einfluß der Lage der CH₃ Gruppe in Pikolinen und Lutidinen als Liganden auf den Grad der chemischen Änderungen der Gruppen NSC in Koordinationsverbindungen des Typs Cu(NCS)₂L₂ (L=2-, 3- und 4-Pikoline, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- und 3,5-Lutidine). Der ausgeprägteste Effekt der CH₃ Gruppe wurde in der Position 4 beobachtet. Dieser Einfluß der Methylgruppe auf das Ausmaß der chemischen Änderungen deutet auch auf die gegenseitige Wirkung der Liganden in Koordinationsverbindungen von Cu(II).

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Résumé L'article a trait à l'influence de la position du groupe CH₂ dans les picolines et lutidines, en tant que ligands, sur le degré des changements chimiques des groupes SCN dans les composés de coordination du type Cu(SCN)₂L₂ (L=2-, 3 et 4-picoline, 2,3-, 2,4-,2,5-, 2,6-, 3,4- et 3,6-lutidine). L'effet le plus prononcé du groupe CH₃ s'observe en position 4. Cette influence du groupe méthyle sur le degré des changements chimiques indique aussi l'influence mutuelle des ligands dans les composés de coordination du Cu(II).

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- , , NCS Cu(NCS)₂,L₂, L=2-, 3- 4- , 2.3-, 2.4-, 2.5-, 2.6-, 3.4- 3.5-. , 4. Cu(II).