Kinetics of the gas-phase reaction between iodine and monogermane and the bond dissociation energy D(H3Ge?H)

The title reaction has been investigated in the temperature range of 403–446 K. Monoiodogermane and di-iodogermane together with hydrogen iodide were the main products, although at high conversions at least one other product was formed. GeH₃I is clearly the primary product. Initial rates were found to obey the rate law over a wide range of initial iodine and monogermane pressures. Secondary reactions (of GeH₃I with I₂) affect the subsequent kinetics, although at sufficiently high initial reactant ratios ([GeH₄]₀/[I₂]₀ ≥ 100) an integrated rate equation fits the data with the same rate constants as the initial rate expression. The observed kinetics are consistent with an iodine atom abstraction chain mechanism, and for the step log k₁ (dm³/mol·s) = (11.03 ± 0.13) – (52.3 ± 1.0 kJ/mol)/RT ln 10 has been deduced. From this the bond dissociation energy D(GeH₃? H) = 346 ± 10 kJ/mol (82.5 kcal/mol) is obtained. The significance of this value, together with derived values for Ge–Ge and Ge–C bond strengths, is discussed.     

Characterization of a new tailoring domain in polyketide biogenesis: the amine transferase domain of MycA in the mycosubtilin gene cluster

We report the expression and characterization of a truncated form of MycA from the Mycosubtilin gene cluster from Bacillus subtilis. The MycA fragment contains a new amino transferase (AMT) tailoring domain, allowing the first detailed study of a PLP-dependent enzyme operating in cis within the PKS and NRPS biosynthetic paradigm. As the AMT domain acts on covalently bound beta-ketothioesters, and is therefore a single-turnover system, electrospray ionization-Fourier transform mass spectrometry (ESI-FTMS) was used to observe the amine-transfer reaction both for amine donor substrate specificity and to regiospecifically determine enzyme-bound intermediates. We confirm the function of the AMT domain, dissect the mechanistic steps of amine transfer, identify the preferred amine source, and localize the beta-ketothioester substrate during amine transfer.     

Morphologie und mechanische Eigenschaften von Celluloseacetat-Fasern mit aufgepfropftem Polyacrylnitril

Ohne Zusammenfassung     

Electron-impact studies—LXIV: Negative-ion mass spectrometry of functional groups. Nitroaniline derivatives

The various fragmentations of the o-nitrobenzanilide molecular anion have been studied by labelling procedures and substituent effects. The loss of HO· from the molecular anion is a specific proximity effect, involving the oxygen of the nitro group and the hydrogen of the amide moiety. The losses of NO· from variously substituted nitrobenzenes are considered in depth and it is suggested that the nitro→ nitrite rearrangement is a radical reaction. Negative-ion mass spectrometry may be used for the structure determination of sulphonamides and nitrophenylhydrazones.     

The simultaneous determination of the major,minor and trace constituents of silicate rocks using inductively coupled plasma spectrometry

An account is given of the evaluation of the inductively coupled plasma spectrometer for the simultaneous determination of a range of major and trace constituents of silicate materials. Procedures which have been used for the routine analysis of silicates are presented, and the spectral lines used noted. The results are evaluated from analyses of international rock standards and it is suggested that the method has considerable potential in silicate analysis, offering some advantages over alternative methods.