Conformational structure of N-methylpropionamide and N-methylisobutyroamede. NMR shift reagent and IR study

The structures of the stable conformers of N-methyjpropionamide and N-methyliso-butyroamide in CCl₄, solution were determined by a combination of IR spectroscopy and NMR spectroscopy with lanthanide shift reagents. N-methyl-propionamide was found to exist in the form of two rotational isomers, 1 and 2, with the ethyl group twisted out of the plane of the amide bond by the angles Ψ = 140 and 20°, respectively. For these two conformers, the enthalpy difference is ΔH = 2.13 ± 0.08 kcal mole^?1 and the entropy difference ΔS = 7.81 ± 0.55 cal mole^?1 grad^?1. N-methylisobutyroamide exists in a single form, with the two C-methyl group positions very close to those found in the two isomers of N-methylpropionamide.     

Alkoholyse von Tris(dimethylamino)-arsin

Alcoholysis of Tris (dimethylamino)arsine The reaction of tris(dimethylamino)arsine with alcoholes and thioles leads to the formation of esters of the general formula As(XR)₃ (X = O and S). The reaction is a suitable preparative method for the synthesis of the esters As(XR)₃ (X = O and S). By alcoholysis in steps results an equilibrium system containing the molecules AsX₃, AsX₂Y, AsXY₂, and AsY₃ (X = OR, Y = N(CH₃)₂).     

Determination of the solubility of organic compounds

Summary Estimations of solubility are carried out by observing with a magnifying lens the substance while it is exposed to air laden with vapor of the solvent.

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Zusammenfassung Teilchen der Substanz werden auf einem schmalen Objektträger abwechselnd einem mit dem Dampf des Lösungsmittels beladenen und einem reinen Luftstrom ausgesetzt, während sie durch ein Vergrößerungsglas beobachtet werden. Der zur Verflüssigung erforderliche Zeitraum ist offen-kundig durch den Löslichkeitsgrad bedingt.

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Résumé Une petite particule de substance placée sur une petite lame porte-objet est soumise alternativement à un courant d'air chargé de la vapeur du solvant et à un courant d'air pur tandis qu'elle est observée à l'aide d'une loupe. Le temps nécessaire à la liquéfaction dépend évidemment du degré de solubilité de la substance.

     

Neutron Diffraction Analysis of H3Co2[C5H2(t-Bu)3]2, a Molecule with a Triply Hydrogen-Bridged Metal–Metal Bond: Some Comments on Structural Patterns in M(μ-H)nM Systems (n=1, 2, 3, 4)

The structure of H₃Co₂[C₅H₂(t-Bu)₃]₂ has been analyzed by low-temperature single-crystal neutron diffraction techniques, and shown to consist of two CoCp moieties with three hydride ligands bridging the central Co–Co bond. Despite a fairly extensive twinning problem, the structure could be solved and successfully refined to a final R factor of 9.2% for 2024 reflections. Average molecular parameters in the H₃Co₂ core of the molecule are as follows: Co–Co=2.275(21) Å, Co–H=1.637(16) Å, HH=2.050(20) Å, Co–H–Co=88.0(9)°, H–Co–H=77.0(7)°. Also included in this paper is a discussion on the molecular dimensions of symmetric hydride-bridged dinuclear systems (M(-H)_nM, n=1, 2, 3, 4) that have been studied to date by neutron diffraction.     

Nanobodies: Chemical Functionalization Strategies and Intracellular Applications

Nanobodies can be seen as next‐generation tools for the recognition and modulation of antigens that are inaccessible to conventional antibodies. Due to their compact structure and high stability, nanobodies see frequent usage in basic research, and their chemical functionalization opens the way towards promising diagnostic and therapeutic applications. In this Review, central aspects of nanobody functionalization are presented, together with selected applications. While early conjugation strategies relied on the random modification of natural amino acids, more recent studies have focused on the site‐specific attachment of functional moieties. Such techniques include chemoenzymatic approaches, expressed protein ligation, and amber suppression in combination with bioorthogonal modification strategies. Recent applications range from sophisticated imaging and mass spectrometry to the delivery of nanobodies into living cells for the visualization and manipulation of intracellular antigens.     

Microelectrochemical investigation on aluminium–steel friction welds

Aluminium–steel friction welds (AlMgSi0.5/C35 and AlMgSi0.5/X5CrNi18‐10) were electrochemically investigated in a NaAc/HAc buffer (pH 5.9) and 0.1 mol/l NaCl using the microcapillary technique. This technique allows a lateral resolution of electrochemical measurements. However, microscopic investigations and scanning electron microscopy/energy dispersive X‐ray SEM/EDX measurements show that the reaction zone (RZ) and the heat affected zone (HAZ) of the welds are smaller than the microcapillary diameter. This paper discusses the advantages and limitations of the microcapillary technique in view of friction welds. Nevertheless, the electrochemical experiments allow a clear detection of the changing active surface area and the correlation to the microstructure (intermetallics). The application of microcapillary measurements on samples which were exposed in marine climate for 2 years shows a good correlation between the local potential measurements and the local corrosion phenomena. Copyright © 2010 John Wiley & Sons, Ltd.     

Important aspects in the formulation of solid–fluid debris-flow models. Part II. Constitutive modelling

This article points at some critical issues which are connected with the theoretical formulation of the thermodynamics of solid–fluid mixtures of frictional materials. It is our view that a complete thermodynamic exploitation of the second law of thermodynamics is necessary to obtain the proper parameterizations of the constitutive quantities in such theories. These issues are explained in detail in a recently published book by Schneider and Hutter (Solid–Fluid Mixtures of Frictional Materials in Geophysical and Geotechnical Context, 2009), which we wish to advertize with these notes. The model is a saturated mixture of an arbitrary number of solid and fluid constituents which may be compressible or density preserving, which exhibit visco-frictional (visco-hypoplastic) behavior, but are all subject to the same temperature. Mass exchange between the constituents may account for particle size separation and phase changes due to fragmentation and abrasion. Destabilization of a saturated soil mass from the pre- and the post-critical phases of a catastrophic motion from initiation to deposition is modeled by symmetric tensorial variables which are related to the rate independent parts of the constituent stress tensors.