Tetrazene–Characterization of Its Polymorphs

The reinvestigation of tetrazene single crystalline material by means of X-ray methods resulted in a slightly different structure when compared to previously published data. Reaction conditions responsible for different crystalline modification formation were investigated. Newly described C form was found to be the primary reaction product and the combined action of temperature and the presence of water over time is required for the transition to the A form. Both forms were described by X-ray powder diffraction. Tetrazene was also subjected to infrared and Raman spectroscopy, which allowed differentiating between the forms. The molecule was isotopically labeled with 15N atoms at two different locations (ring and nitrogen sidechain) and employed in assigning vibrational modes to the resulting bands. Differences between sensitivities to mechanical stimuli of the two modifications were investigated and found industrially insignificant. In the same vein, the performance of either modification in primer composition and primer was identical.

Isolation and characterisation of enzymatic zearalenone hydrolysis reaction products

Zearalenone (ZEA) is an oestrogenic mycotoxin produced by several Fusarium species, and it frequently contaminates cereals used for food or animal feed. A ZEA-lactonase of Gliocladium roseum was previously described to hydrolyse ZEA to an unstable intermediate, which spontaneously decarboxylates to non-oestrogenic, decarboxylated hydrolysed ZEA (DHZEN). We expressed a codon-optimised version of the ZEA-lactonase (ZHD101) gene of G. roseum MA 918 with a secretion leader in Pichia pastoris and purified the recombinant enzyme from culture supernatant by His-tag mediated affinity chromatography. After incubation of the enzyme with ZEA, we detected the previously elusive primary reaction product hydrolysed ZEA (HZEN) by liquid chromatography tandem mass spectrometry, purified it by preparative high-performance liquid chromatography, and confirmed its postulated structure ((E)-2,4-dihydroxy-6-(10-hydroxy-6-oxo-1-undecen-1-yl)benzoic acid) by nuclear magnetic resonance techniques. Spontaneous decarboxylation to DHZEN ((E)-1-(3,5-dihydroxy-phenyl)-10-hydroxy-1-undecen-6-one), but not to a previously reported isomer, was observed. Biomass resuspensions of G. roseum strains MA 918 and the strains used for previous work, NBRC 7063 and ATCC 8684, all converted ZEA to HZEN, DHZEN, and further unknown metabolites. We studied partitioning of HZEN and DHZEN between aqueous phases and organic solvents, and found that HZEN did not partition into chloroform as extraction solvent, under the conditions used by previous authors. In contrast, extraction with ethyl acetate at pH 2.0 was suitable for simultaneous extraction of HZEN and DHZEN. The detection of HZEN and its availability as an analytical standard may assist further work towards possible application of ZEA-lactonase (e.g. determining kinetic parameters) for detoxification of ZEA.

Synthesis of sodalite from Brazilian kaolin wastes

Kaolin wastes from the Capim and Jari regions (Brazil) were used to produce sodalite under the same conditions used in the Bayer process, in order to control its formation when necessary. Of the two kaolin source materials, the kaolinite from the Jari region was more reactive in the synthesis of sodalite, which is attributed to the low degree of structural order of this clay mineral which increased its reactivity. At a temperature of 150°C and with a Na/Al ratio of 2, although the kaolinite did not react completely, sodalitewas the primary reaction product. An increase in the temperature to 200°C provoked the complete reaction of the kaolinite only for the products in which carbonate and sulfate were used. With a Na/Al ratio >2 and for both of the temperatures, the kaolinite reacted completely to form sodalite.

Effect of pH on the mechanism of OClO· oxidation of aromatic compounds

Contrary to previous reports, the reaction mechanism of chlorine dioxide (OClO·) with benzyl alcohols involves both radical cation and benzyl radical mechanisms dependent on pH. The primary reaction product between OClO· and 1-(3,4-dimethoxy-phenyl) ethanol at pH 8 is 3,4-dimethoxyacetophenone. At pH 4 no acetophenone was observed; the majority of the degradation products were chlorinated and aromatic ring-oxidized compounds. A primary kinetic isotope effect (kH/kD = 2.05) was observed in the reaction of OClO· with 1-(3,4-dimethoxy-phenyl)-(1-2H) ethanol at pH 8, but was absent at pH 4 (kH/kD [Formula: see text] 1). Similarly, the corresponding methyl ether (4-(1-methoxy)ethyl-1,2-dimethoxybenzene) was substantially less reactive at pH > 6. On the basis of these results, competing pH-dependent reaction mechanisms have been proposed, where at high pH OClO· reacts with benzyl alcohols via a OClO·–benzyl alcohol complex.Key words: chlorine dioxide, mechanism, kinetic isotope effect, aromatic radical cation, benzyl radical.

Combustion synthesis of cubic Al3Ti alloys

Combustion synthesis of elemental powder compacts has been used to produce alloys with compositions corresponding to Al3Ti, Al73Ti24Cr3, and Al67Ti25Cr8. The binary composition exhibits a strong exothermic reaction at ∼665 °C, resulting in formation of single phase Al3Ti with the tetragonal DO22 structure. The heat of formation of the compound at 298 K, δHf(298), was estimated from peak reaction temperature measurements to be −35.0 kJ mol−1. Additions of Cr lowered the reaction initiation temperature and resulted in the formation of intermediate products attributed to Al–Cr reactions. The DO22 structure remained the primary reaction product in Cr-containing alloys. The Cr particles did not completely dissolve during initial reaction; an additional heat treatment at 1200 °C or above was required to homogenize the material, resulting in partial or complete transformation of the DO22 structure to the cubic L12 structure, depending upon Cr content. Homogenization at 1250 °C for 4 h produced material consisting approximately of a 50-50% mixture of the DO22 and L12 structures for Al73Ti24Cr3, and 100% L12 for Al67Ti25Cr8. In all cases, reaction at ambient pressure was accompanied by swelling, resulting in final densities less than 60% of theoretical. Application of external pressure, either during or subsequent to combustion synthesis, produced near theoretical density materials exhibiting a homogeneous and equiaxed microstructure.

Evaluation of an Scs-6/Ti-22al-23nb “Orthorhombic” Composite

ABSTRACTstudy was undertaken to examine the attributes of utilizing a high niobiumcontaining titanium aluminide (orthorhombic) composition, specifically Ti-22AI-23Nb (a%), for use as a matrix for a continuously reinforced metal matrix composite. Both unreinforced “neat” panels and 35v% 4-ply unidirectional ([0]4) SiC (SCS-6) panels were fabricated by HIP'ing using a foil / fiber / foil approach. The microstructure of these panels were examined via optical, scanning electron and transmission electron microscopy. Reaction zone kinetics including both the primary reaction product and any beta-depleted zone growth were determined at 982°C. Analytical electron microscopy was employed to identify fiber / matrix interfacial compounds as well as local phases and their associated chemistries. Preliminary mechanical properties were obtained which included: longitudinal and transverse tensile, matrix thermal stability, thermal fatigue, thermal mechanical fatigue and transverse composite creep. The results were compared with panels fabricated from the baseline matrix composition, Ti-24AI-11 Nb.

Reaktionen von Titantetrachlorid mit Bistrimethylsilylsulfid. Die Kristallstrukturen von (NEt4)2[TiSCl4], (PPh4)2[TiSCl4]·2CH2Cl2, (PPh4)2[Ti3O(S2)3Cl6]CH3CN und Ti4O(S2)4Cl6 / Reactions of Titanium Tetrachloride with Bistrimethylsilyl Sulfide. Crystal Structures of (NEt4)2[TiSCl4], (PPh4)2[TiSCl4]·2CH2Cl2, (PPh4)2[Ti3O(S2)3Cl6]CH3CN and Ti4O(S2)4Cl6

The reaction of TiCl4 with (Me3Si)2S in dichloromethane yields black, insoluble, impure TiSCl2. In the presence of oxygen, additionally Ti3O(S2)3Cl4 and Ti4O(S2)4Cl6 are formed. By reactions of TiSCl2 with NEt4Cl and PPh4Cl in dichloromethane (NEt4)2[TiSCl2] and (PPh4)2[TiSCl4] ·2CH2Cl2 are formed, respectively. They were characterized by their IR spectra and by X-ray crystal structure determinations. They contain the square-pyramidal [TiSCl4]2- ion. which has a rather short Ti = S bond of 211.1(2) pm. Crystal data: (NEt4)2[TiSCl4]: tetragonal. P4/n, a = 923.9(3). c = 1406.7(2) pm. Z = 2. 966 unique observed reflexions. R = 0.053; positionally disordered ethyl groups. (PPh4)2[TiSCl4] · 2CH2Cl2: triclinic, P1, a = 1009.7(4), b = 1115.1(3). c = 1242.1(5) pm, α = 70.27(3), β = 79.06(3), γ = 81.37(3)°, Z = 1, 1504 reflexions, β-(AsPh4)2UCl6·2CH2Cl2 structure type, high R = 0.107 due to positional disorder of the anion. Addition of NEt4Cl or PPh4Cl in CH2Cl2 to the primary reaction product in presence of O2 yields (NEt4)2[Ti3O(S2)3Cl6] and (PPh4)2[Ti,O(S2)3Cl6] · CH2Cl2, respectively. Upon recrystallization of the latter from acetonitrile, (PPh4)2[Ti3O(S2)3Cl6] · CH3CN is obtained which forms triclinic crystals with a = 1138.8(3). b = 1268.8(4), c = 2166.4(6) pm, α = 101.26(3). β = 97.21(2). γ = 109.24(2)°, Z = 2, P1 (3053 reflexions, R = 0.070). The [Ti3O(S2)3Cl6]2- ion has a cluster-like structure with Ti atoms at the vertices of a triangle, with a μ3-O bridging atom and with tree bridging disulfide groups. Crystal data for Ti4O(S2)4Cl6: monoclinic, C2/c, a - 917.3(2), b - 1632.5(2), c = 1268.5(2) pm, β - 108.35(2)°, Z = 4. 1009 reflexions. R = 0.027. In the Ti4O(S2)4Cl6 molecule, four Ti atoms form a distorted tetrahedron around an μ4-O atom; two edges of the tetrahedron are spanned by chloro bridges, four edges by disulfide bridges.

The photochemistry of phenanthrene-substituted molecules

The photochemistry of 3-methyl-3-(9-phenanthryl)-1-butene was examined as part of an investigation into the effects of having two π chromophores of widely different energies participating in a di-π-methane rearrangement. We observed both direct and sensitized reactivity with quantum yields [Formula: see text] and [Formula: see text]. The primary reaction product from both direct and sensitized photolyses was 1,1-dimethyl-2-(9-phenanthryl)cyclopropane. However, in practice this product was obtained only from sensitized irradiations where it was almost completely unreactive. The triplet reactivity is unusual in that the typical free rotor decay exhibited by triplets does not lead to inhibition of di-π-methane reactivity in this case. This point is discussed. The intersystem crossing efficiency of the phenanthryl vinyl methane reactant was obtained from the sensitization of biacetyl phosphorescence by the phenanthrene derivative at varying biacetyl concentrations. This was [Formula: see text]. This result and the bracketing relationships signify that essentially all of the direct irradiation rearrangement utilizes T1. In addition, from these experiments, 3kd(tot), was determined as 5.8 × 103 s−1. Similarly,3kr = 250 s−1 which is the slowest di-π-methane rearrangement encountered thus far. The rearrangement of the cyclopropane product to form 2-methyl-4-(9-phenanthryl)-1-butene was also investigated. [Formula: see text] was determined to be 0.091 and [Formula: see text] was determined as 0.00072. Thus the interesting contrast was encountered in which the di-π-methane rearrangement proceeds from the triplet while the rearrangement of the cyclopropane product proceeds most efficiently from the singlet.