Thermal Decomposition of NbCl2(OCH3)3

The thermal decomposition of NbCl₂(OCH₃)₃ in an atmosphere of argon or oxygen was carried out and the overall reactions of them were described. The representative reactions were determined as: The structures of the solids produced by the pyrolysis were examined. TT-Nb₂O₅ was one of the main solid products and it contains a small amount of chlorine atoms in place of oxygen atoms. Then, it is suggested that the so-called TT-modification might be composed of not only one structure, but of various structures represented by the equation, Nb_6n?2X_16n?6 (n = 1, 2, 3, …).     

Bioanalytik für Einsteiger.Diabetes,Drogen und DNA. Von Reinhard Renneberg.

Spektrum Akademischer Verlag, Heidelberg 2008. 284 S., geb., 34.95 €.—ISBN 978‐3827418319

     

Flash Photolysis of 2,4,6-Trinitrotoluene Solutions

Flash photolysis of 2,4,6-trinitrotoluene solutions (TNT) indicates a photochemically induced isomerization leading to the aci-quinoid isomer with an absorption maximum at 460 nm in nonpolar solvents, or the conjugate base of the aci-quinoid isomer with absorption maxima at 500, 540, and 630 nm in polar solvents. Both species, the quinoid isomer and the conjugate base, have transient existence and their identification was based on detailed spectroscopic and kinetic studies presented here. The magnitude of the negative charge on the transient conjugate base was determined with salt effect experiments and found to be equal to unity.     

Bridged polyaromatics: Synthesis and isomorphous properties of polymers and oligomers containing O,S, CH2 bridges

A study of the isomorphous relationships existing among five crystalline polyaromatic polymers containing O, S, CH₂ bridges, i.e., where Ph is phenyl, is reported. Appropriate series of oligomers corresponding to these polymers have also been prepared in order to investigate how the solid-state properties of the oligomers correlate with those of the polymers. A preliminary x-ray analysis is reported showing that the polymers are actually isostructural.     

Synthesis of 2‐alkyl‐4,5‐aryl‐2H‐[1λ6,2,3,6]‐thiatriazine‐1,1‐dioxides

Sulphamoyl chlorides and chlorosulphonyl isocyanate react with monosubstituted hydrazones and alkylhydrazonates to sulphamoyl hydrazones and sulphamoyl hydrazonates respectively. Reaction of benzil monoalkylhydrazones with chlorosulphonyl isocyanate results in formation of 2‐alkyl‐4,5‐aryl‐2H‐ [1λ⁶,2,3,6]‐thiatriazine‐1,1‐dioxides.     

Gas phase reaction of heptafluoroisopropyl radicals with carbon tetrachloride

The reaction was investigated in the gas phase over the range 80–225°C using the photolysis of heptafluoroisopropyl iodide as the source of radicals. The rate constant, based on the value of 10^13.36 cm³ mol^?1 s^?1 for the recombination of i-C₃F₇ radicals, is given by where θ = 2.303 RT/cal mol^?1. Arrhenius parameters for chlorine abstraction from CCl₄ by CF₃, C₂F₅, n-C₃F₇, and some hydrogenated radicals are compared.     

Bildung siliciumorganischer Verbindungen. LVI. Reaktionen Si- und C-chlorierter 1,3,5-Trisilapentane mit CH3MgCl

Formation of Organosilicon Compounds. LVI. Reactions of Si- and C-Chlorinated 1,3,5-Trisilapentanes with CH₃MgCl (Cl₃Si? CCl₂)₂SiCl₂ (1) reacts with an excess of meMgCl (me = CH₃) forming me₃Si? C?C? Sime₃ (2), Sime₄, H₂C?C(Sime₃)[CH(Sime₃)₂] (3) as main products and (me₃Si)₂C? CH(Sime₃) and as by-products. The cleavage reaction of (1) to (2) and (3) does not occur when the meMgCl-concentration is lowered. The reaction is started by the formation of a GRIGNARD reagent at a CCl-group in compound (1). Cl₃Si? CCl₂? SiCl₂? CH₂? SiCl₃ forms with ; me₃Si? CCl₂? SiCl₂? CHCl? SiCl₃ forms (me₃Si)₂C?CH(Sime₃). A reaction sequence is given.     

Molecular confirmation and crystal structure of the β form of poly(ethylene oxybenzoate)

The crystal structure of the β form of poly(ethylene oxybenzoate) was analyzed by x-ray diffraction. Four nearly extended molecular chains pass through a unit cell with parameters a = 8.19 Å, b = 11.07 Å, c (fiber axis) = 19.05 Å, β = 114.8°, and the space group P2₁/n-C. The structural difference between the α and β forms is mainly due to the internal rotation angles for the virtual bond and the ? CH₂? CH₂? bond. They are essentially in trans confirmation in the β form, while the α form contains cis and gauche (? CH₂? CH₂? ) conformations.     

Amino-phosphane. X. Einige Additionsreaktionen von N-Diphenylphosphinotetraphenyldiphosphin-imid

Diphenylphosphorous chloride and methyl iodide add readily to the N-bonded P(III)-atom of (C₆H₅)₂P? P(C₆H₅)₃?N? P(C₆H₅)₂ forming the salts [(C₆H₅)₂P? P(C₆H₅)₂ N P(C₆H₅)₂? P(C₆H₅)₂]Cl and [(C₆H₅)₂P? P(C₆H₅)₂ N P(C₆H₅)₂. CH₃]I, respectively. A similar behaviour is observed with sulfur: Under mild conditions (C₆H₅)₂P? P(C₆H₅)₂?N? P(C₆H₅)₂ = S is formed but forcing conditions are required to produce S = P(C₆H₅)₂? P(C₆H₅)₂?N? P(C₆H₅)₂?S. The monosulfide is also obtained by treating (C₆H₅)₂P(S)N[Si(CH₃)₃]₂ with diphenylphosphorous chloride, indicating the favoured formation of the phosphazene system as compared with the phosphazane system Confirmation of the structures comes from ³¹P nmr and IR data, and for the sulfides also from their degradation with bromine.     

Darstellung,Eigenschaften und Molekülstruktur eines Titan-tris(diazadien)-Komplexes

Preparation, Properties, and Molecular Structure of a Titanium-tris(diazadiene) Complex (R = i-C₃H₇) 1 was obtained by reaction of TiCl₄ · 2 THF with Li₂(NR? CH = CH? NR) in the presence of the ligand molecules. The compound was characterized by ¹H-, ¹³C-n.m.r., and mass spectroscopy. The molecular structure was determined by X-ray diffraction. The bonding distances in the identically coordinated diazadiene ligands are similar to those of radical.     

Ab-initioMRD–CI calculations on a C?NO2 decomposition pathway of nitrobenzene

To study molecular decomposition pathways it is necessary to use ab initio multireference determinant–configuration interaction or MCSCF (multiconfiguration SCF ) calculations. The MRD –CI (multireference double excitation–configuration interaction technique of Buenker and Peyerimhoff) calculations on the decomposition pathway of nitrobenzene were carried out using all of the occupied molecular orbitals in the region of the bond being dissociated, plus all of the virtual orbitals. An effective CI Hamiltonian was used into which were folded the effects of all of the occupied molecular orbitals from which excitations were not allowed. So far we have investigated the lowest ¹A₁, ³A₁, ¹A₂, ³A₂, ¹B₁, ³B₁, ¹B₂, ³B₂ states and are investigating the higher states. Our results show a wealth of structure in the potential energy surfaces for the various electronic states of nitrobenzene as a function of distance. A number of the states are predissociative and change dominant configuration one or more times along these potential energy surfaces.     

The potential energy surface for the [C2H2O]+˙ system: The ketene radical cation [CH2CO]+˙ and its isomers

Ab initio molecular orbital calculations with large, polarization basis sets and incorporating valence electron correlation have been employed to examine the [C₂H₂O]^+˙ potential energy surface. Four [C₂H₂O]^+˙ isomers have been identified as potentially stable, observable ions. These are the experimentally well-known ketene radical cation, [CH₂?C?O]^+˙ (a), and the presently unknown ethynol radical cation, [CH₂?C? OH]^+˙ (b), the oxirene radical cation (c) and an ion resembling a complex of CO with [CH₂]^+˙, (d). The calculated energies of b, c and d relative to a are 189, 257 and 259 kJ mol^?1, respectively. Dissociation of ions a and d is found to occur without reverse activation energy.     

Synthesis and psychotropic properties of furyl- and thienyl-germatranes

Trihalogermyl-furans and -thiophenes were prepared by inserting germanium dibromide (GeBr₂) generated from the dibromogermane(II) dioxanate complex into the carbon-halogen bond of halo-furans and -thiophenes. Their ethanolysis and transesterification by triethanolamine yielded the germatranes which were subjected to psychotropic activity assays. The psychotropic properties of germatranes were found to depend on the type of the heterocycle and on the position of the germatrane moiety.     

The pyrolyses of tri- and tetramethylethylene in the presence of nitric oxide

The pyrolyses of trimethylethylene and tetramethylethylene have been investigated in the presence and absence of nitric oxide. It appears that apart from a unimolecular split, e.g., a disproportionation reaction such as may play an important role in initiation. Nitric oxide had no effect on H₂ production, which is probably a molecular process. There was similar behavior of both compounds in the presence of NO, indicating that the olefinic hydrogen atom does not play a decisive role. Other aspects of the mechanisms are discussed.     

Fluorsulfonylstickstoffverbindungen

The reactions of fluorosulfonylurea derivatives with phosphorus pentachloride in carbon tetrachloride leads to and . These compounds are easily fluroinated by arsenic trifluoride to the corresponding fluorosulfonyl derivatives. It was shown that PCl₅ is reliable for the fluorine-chlorine exchange. Isocyanate esterchlorides as well as carbonyl-fluoride derivatives react with compounds which have an active hydrogen atom. By this way were prepared: . By hydrolysis of , is probably formed as the first reaction product. The acid could be trapped with tetraphenylphosphoniumchloride as a well-cristalline salt. Fluorosulfonyl isocyanate reacts with aldehydes to the following compounds: FSO₂N ? CHCH₃, FSO₂N ? CHC₂H₅, FSO₂N ? CH? CH(CH₃)₂ and FSO₂N ? CHC₆H₅. The physical and chemical properties as well as IR and NMR spectra of the compounds are described and, in part, compared and discussed.     

Reactions of Cl2P3/2: Absolute rate constants for reaction with H2, CH4, C2H6, CH2Cl2, C2Cl4, and c?C6H12

The absolute rate constants have been measured for several gas-phase chlorine atom-molecule reactions at 25°C by resonance fluorescence. These reactions and their corresponding rate constants in units of cm³ mole^?1 sec^?1 are: The effects of varying the substrate pressure, total pressure, light intensity and chlorine-atom source on the value of the bimolecular rate constants have been investigated for all these reactions. Conditions under which no competing side reaction occurs were established and the reported rate constants were measured under these conditions. For reactions (2), (5), (6), (7), and 8, there is a discrepancy of a factor of two between the rate constants measured in this work and values in the literature; it is suggested that this is due to an error in the previously measured value of k/k upon which the relative measurements in the literature ultimately depend.     

Dichloromaleimide chemistry. IV. Preparation of poly(maleimide–ethers) from the reaction of bisdichloromaleimides with bisphenols

A newly discovered reaction between phenols and dichloromaleimides has led to the synthesis of a new class of polymers of high molecular weight. These materials, represented by the general formula may be called poly(maleimide–ethers). Unlike polyimides, these materials are soluble in appropriate solvents and may be cast or compressionmolded into tough, flexible films.     

[2, 3] Sigmatropic Rearrangements on Lithiation of Some Allyl Sulfides. Preliminary communication

In five cases, [2,3] sigmatropic rearrangement of the type has been observed.     

Kinetics of recombination,dismutation, and disproportionation reactions involving neutral ketyl radicals and radical anions

The kinetics of fast elementary recombination of neutral ketyl radicals of benzophenone and its four derivatives (BPH?), the dismutation of benzophenone radical anions, the disproportionation between BPH? and stable nitroxyl radicals, ( ), and the electron transfer have been investigated in both individual solvents and binary mixtures of different viscosities. Reaction (1) for unsubstituted BPH in water, water glycerol, and n-hexane is controlled by diffusion with 2k₁ ? k_diff. In aliphatic alcohols and toluene, which form solvation complexes with BPH?, reaction (1) is diffusion-enhanced and activation-controlled, respectively, with 2k₁ < k_diff. In a viscous solvent such as 1-propanol–glycerol mixture (100 ? η ? 450 cP) reaction (1) is diffusion-controlled. Reaction (2) in alkaline 1-propanol and alkaline 1-propanol–glycerol mixture is activation controlled. The rates of reactions (3) and (4) for benzophenone radicals and nitroxyl radicals of the imidazoline series decrease as the viscosity of the water–glycerol and 1-propanol–glycerol mixtures is increased. The reactions are molecular mobility limited; nevertheless, the numerical values of k₃ (k₄) are 2–6 times as small as the corresponding k_diff values due to the low steric factor of the reactions (therefore called pseudodiffusion-controlled reactions). The theoretical estimates of k₃ (k₄) are in good agreement with the experimental results. The elimination of spin forbiddance in the process of radical recombination in viscous solvents is discussed.     

Spectral Studies of Mercaptoacid Amides III: Nuclear Magnetic Resonance Spectra

NMR spectra of twelve newly synthesised mercaptoacid amides are being reported and discussed. The syntheses and structure of more than thirty mercaptoacid amides have been reported^(1-3) from our laboratories. The study has revealed that N -phenyl-2-mercaptoacetamide and related compounds have intramolecular hydrogen bonded structure (I).