A molecular orbital study of the rotation about the C-C bond in 1,3-butadiene

The geometry and energy of 1,3-butadiene have been calculated using the 6-311G** basis set as a function of the CCCC dihedral angle-0 ° (trans), 30 °, 60 °, 75 °, 90 °, 120 °, 135 °, 150 °, 165 ° and 180 ° (cis)-assuming that the vinyl groups remain planar. Potential minima are located at 0 ° and 141.4 °, with the trans structure more stable than the gauche by 13.2 kJ mol^–1. Potential maxima are located at 76.7 °, giving a barrier height of 25.4 kJ mol^–1 relative to the trans structure, and at 180 ° giving a barrier height of 3.0 kJ mol^–1 relative to the 141.4 °-gauche structure. Using the 6-31G* basis set the inclusion of electron correlation, accounting for about 52% of the correlation energy, was found to produce no significant change in the shape of the potential energy curve. The magnitude of the expectation energy differences is such that both barriers with respect to the 14l.4 °-gauche maximum structure can be categorized unequivocally as attractive-dominant, whereas the values for the energy barrier with respect to the trans structure, although characteristic of a repulsive-dominant barrier at the 6–311G** level, are sufficiently small that higher level calculations might give the opposite result. Analysis of V _nn for the conversion reactions cis 150 °-gauche, trans 60 °-gauche, and trans 90 °-gauche in terms of the individual contributions from the various internuclear interactions shows that nonbonded interactions are important, not only in initiating the destabilization of the crowded cis structure, but also through-out the entire range of CCCC dihedral angles, 0 ° to 180 °.     

Surface enhanced Raman spectra of benzotriazole adsorbed on a copper electrode

The surface enhanced Raman spectrum of benzotriazole (BTAH) adsorbed on a copper electrode has been studied as a function of the potential applied to the electrode. The effect of pH and of the type of halide in the electrolyte solution has also been investigated. The presence of some complexes involving Cu(I), benzotriazole or benzotriazolate (BTA^-) and the halide has been characterized. The protective film formed on copper surface, in the presence of benzotriazole, has been identified as cuprous benzotriazolate [Cu(I)BTA].     

Membrane structure and its correlation with membrane permeability

Methods for the investigation of pore and molecular structure of synthetic membranes are reviewed. Membranes are classified as coarse-porous, fine-porous, and solution-diffusion membranes, on one hand; and homogeneous, asymmetric, and composite on the other, Pore structure of synthetic membranes can be elucidated in detail only by electron and raster electron microscopic investigations. Inspection of molecular structure requires diversely specific test probes such as low-energy neutron scattering and/or diffraction, and gas sorption and permeability measurements, as well as thermodynamic and thermomechanical analysis. Other methods used to elucidate pore and molecular structure of synthetic membranes are discussed and, concurrently, membrane structure is correlated with membrane permeability.     

Zur Kenntnis der Sulfensäurefluoride CF3SF und CF2ClSF sowie deren Dimeren

The Sulfenic Fluorides CF₃SF and CF₂CISF and their Dimers The reactions of R_fSCl (R_f = CF₃, CF₂Cl) with HgF₂ and AgF give R_fSF and the dimer product R_fSF₂SR_f in high yield and various ratios, in contrast, activated KF leads only to R_fSF in low yield. A complex of transition metal and sulfenic halide as an intermediate step is discussed for the dimerisation. As liquid CF₃SF₂SCF₃ disproportionates into CF₃SF₃ and CF₃SSCF₃ and the hydrolysis of CF₃SF₂SCF₃ gives the stable compound CF₃S(O)SCF₃ · PF₃ reacts with R_fSF as well as with R_fSF₂SR_f to R_fSPF₄. The products of the spontaneous decomposition of CF₂ClSF were investigated. I.r., n.m.r., and mass spectra are reported and discussed. It was possible to carry out vapour pressure measurements of CF₂ClSF.     

Stoffwechselprodukte von Mikroorganismen 6-Chlorgenistein und 6,3′-Dichlorgenistein. 164. Mitteilung

Metabolites from Microorganisms, 6-Chlorogenistein and 6,3′-Dichlorogenistein A strain of Streptomyces griseus produced chlorinated metabolites in media containing soybean meal. Two of these metabolites were isolated together with a chlorine free compound which could be identified as the isoflavone genistein (I) by its spectral properties and by comparison with an authentic sample. By NMR. and mass spectroscopy the chlorinated compounds were shown to be 6-chlorogenistein (II) and 6,3′-dichlorogenistein (III). The 7-glucoside of genistein is a constituent of soybean meal; it is hydrolysed and chlorinated by Streptomyces griseus.     

Anisotropy of the T-T absorption spectra of naphthalene and phenanthrene

The naphthalene absorption in the spectral region of 3500–4100 Å consists of two perpendicularly polarized band systems. This can be shown by polarization measurements. The arguments given do not allow a decision as to whether or not the short axis polarized band is the ³A_g⁻ ← ³B_iu⁺ transition or an induced vibronic band of the ³B_3g⁻ ← ³B_iu⁺ transition generated by a b_3g vibration mode. The T-T polarization of phenanthrene as a function of the excitation wavenumber is quantitatively compared with the equivalent S₁ ← S₀ fluorescence polarization. There is a good agreement between the calculated and the measured curve.     

Die automatisierte Bestimmung von Kohlenstoff und Wasserstoff. IV

Zusammenfassung Ein Gemisch von-Naphthylisocyanat mit etwa 6 1,4-Diazabicyklo-[2,2,2]-oktan (10–15 ml) reagiert quantitativ und sofort mit mg-Mengen Wasser unter Bildung von Kohlendioxid, das anschließend automatisch titriert wird. Wassermengen von etwa 0,3–3 mg lassen sich in etwa 8 min mit einer Standardabweichung von 0,8% rel. bestimmen.

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The automatic determination of carbon and hydrogen. IV

Summary A mixture of about 10–15 ml of-naphthylisocyanate with about 6%. 1,4-diazabicyclo [2,2,2]-octane reacts instantaneously and quantitatively with water in mg quantities. The resulting carbon dioxide is automatically titrated. Amounts of water of about 0.3–3 mg were determined within 8 min. with a standard deviation of 0.8% rel.

     

Beitrag zur Stickstoffschnellbestimmung nach Merz

Zusammenfassung Einige Änderungen an der Apparatur zur Stickstoffschnellbestimmung nachMerz wurden vorgenommen. Dadurch wird erreicht, daß zwischen den einzelnen Verbrennungen Sauerstoff das Verbrennungsrohr durchspült und vor dem Reduktionsrohr nach außen tritt. Der Verbrennungsraum ist daher bereits zu Beginn jeder Analyse mit Sauerstoff gefüllt, wodurch günstigere Bedingungen für die schlagartige Verbrennung erzielt werden. Der Umbau der von der Firma Heraeus gelieferten Apparatur und die Herstellung eines Oxydationskatalysators (Kobaltoxid-Wolframoxid) werden beschrieben.

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Contribution to the rapid nitrogen determination according to merz

Summary The apparatus for rapid nitrogen determination according toMerz has been modified. Between each two combustions, oxygen is flushed through the combustion tube and is vented before the reduction tube. Therefore, at the beginning of each analysis, the combustion chamber is filled with oxygen, providing a more favorable atmosphere for the rapid ignition. The alterations in the Hereaus apparatus and the preparation of an oxidation catalyst (cobalt oxide and tungsten oxide) are described.

     

Synthesis of phenylated phthalimides. The diels-alder reaction of tetraphenylcyclopentadienone with maleimides

A series of phenylated dihydrophthalimides has been synthesized by the Diels-Alder reaction of tetraphenylcyclopentadienone with maleimide, N-phenylmaleimide, and N,N'-o-, -m-, and -p-phenylenedimaleimide. Subsequent dehydrogenation of these compounds yielded the corresponding phenylated phthalimides. These phthalimides were also obtained in one step when the initial reactions were carried out in refluxing nitrobenzene.     

Rydberg states in fluorinated benzenes; hexa-, penta-, and monofluorobenzene

Spectra of fluorobenzene (FB), pentafluorobenzene (PFB) and hexafluorobenzene (HFB) from 50000 to 93000 cm⁻¹ are presented. Rydberg series converging to the first and to a higher ionization limit are found in each molecule. The orbital natures of the excited states and ions are discussed.