The use of ceric ammonium nitrate in pyrrole chemistry
Ceric ammonium nitrate, in aqueous acetic acid buffered with sodium acetate, rapidly oxidizes 2,2′-dipyrromethanes to the corresponding 2,2′-dipyrroketones.
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The Twist Structure of Open-End Yarns
A single measurement of twist is insufficient to typify open-end yarns because the twist (tpi) of the fibers comprising the yarn core is different from those comprising the outer sheath, and both are usually lower than the machine value. The differences may be expressed in terms of a twist gradient which is a function…
Studies on Phenylpyruvic Acid
The tautomerism of phenylpyruvic acid (PPA) and its sodium salt was investigated. The 1H and 13C spectra of PPA in aprotic solvents and in methanol show almost complete prevalence of the enol form, whereas the keto form prevails only in water. The Z configuration was assigned to the sole enol tautomer present on the b…
Different Temperature Dependence of Magnetic Susceptibility of Different Molecular Complexes of Copper (II) with 7-Hydroxy-4-methyl-5-aza-hept-4-en-2-on
Abstract Two principally different molecular structures in the crystalline state are known from the copper (II) complex with 7-hydroxy-4-methyl-5-aza-hept-4-en-2-on. The magnetic susceptibilities of three forms of this compound [α-(CuEIA) 4 , β-(CuEIA) 4 , and β-(CuEIA) 4 ·2 C 6 H 6 ] have been measured in the tempera…
NMR and molecular dynamics in the choline ion
Proton magnetic resonance spectra of three crystalline choline halides have been obtained over a temperature range of 77 to 440 °K. In all of these materials the line shapes are strong functions of temperature with multiple changes observed for each substance. Above 353 °K, the temperature at which a crystal–crystal p…
Kristall‐ und Molekülstruktur des 1,2‐Heptalendicarbonsäure‐dimethylesters
Eine überraschend einfache Heptalen‐Synthese besteht in der Umsetzung von Azulen ( 1 ) mit Acetylendicarbonsäure dimethylester. Die Ausbeute an ( 2 ) beträgt 15%. Die Synthese ist auch auf alkylierte Azulene anw end bar. Die detaillierte Struktur des Produktes ( 2 ) ergab sich aus einer Röntgenanalyse. magnified image
Cation Distribution and Magnetic Exchange Interactions in MgFe2O4 Studied by the Mössbauer Effect
Abstract The quenching temperature dependence of the magnetic hyperfine fields at the Fe 57 nucleus in magnesium ferrite has been investigated by the Mössbauer effect technique. Since the outer absorption lines are broad and asymmetric, the average magnetic hyperfine field is calculated from the two most inner lines.…
Ferroelasticity in ReP5O14 (Re : La-Tb)
The ferroelasticity of rare earth pentaphosphates, ReP 5 O 14 (Re : La, Ce, Pr, Nd, Sm, Eu, Gd and Tb) which belongs to the species mmmF2/m is studied by DSC, Weissenberg camera and polarizing microscope. Anomaly of heat capacity at the ferroelastic transition point (second order), ferroelastic hysteresis loop, space…
Silver(I)-promoted reactions of strained hydrocarbons. Oxidation vs. rearrangement
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSilver(I)-promoted reactions of strained hydrocarbons. Oxidation vs. rearrangementGerald F. Koser and J. Neil FairclothCite this: J. Org. Chem. 1976, 41, 3, 583–585Publication Date (Print):February 1, 1976Publication History Published online1 May 2002Published inissue 1 Febr…
Effective quantum efficiency of photodetectors for photon energies much larger than threshold
Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text T. Hirschfeld, "Effective quantum efficiency of photodetectors for photon energies much larger than threshold," Appl. Opt. 15, 305-305 (1976) Export Ci…
New Coenzymically‐Active Soluble and Insoluble Macromolecular NAD + Derivatives
Reaction in dimethyl sulfoxide of nicotinamide 8-bromoadenine dinucleotide with the disodium salt of 3-mercaptopropionic acid afforded nicotinamide-8-(2-carboxyethylthio)adenine dinucleotide, a new NAD+ analogue functionalized at the adenine C-8 position by an omega-carboxylic side chain. Carbodimide coupling of the l…
On the Initiation of Crevice Corrosion on Stainless Steel
The site of crevice corrosion initiation on stainless steels has been investigated. It has been found that the initiation takes place at sulfide inclusions situated at the junction between a covering layer and the free metal surface with a portion of the inclusion covered and the rest exposed to the solution. A mechan…
Gas chromatographic and nuclear magnetic resonance determination of linear formaldehyde oligomers in formalin
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTGas chromatographic and nuclear magnetic resonance determination of linear formaldehyde oligomers in formalinWim. Dankelman and Jacq. M. H. DaemenCite this: Anal. Chem. 1976, 48, 2, 401–404Publication Date (Print):February 1, 1976Publication History Published online1 May 200…
Structural Analysis of Sepiolite by Selected Area Electron Diffraction—Relations with Physico-Chemical Properties
Abstract The electron structural analysis of a Madagascar sepiolite (Ampandrandava) was carried out by selected area electron diffraction obtained from monocristals. Fourier projections, derived from the experimental intensity of Okl , hOl and hkO reflections, show that the Mg 2+ cations on the edges of the sheets are…
Determination of molecular weight distribution of cellulose by conversion into tricarbanilate and fractionation
Abstract Two samples of cellulose (molecular weight 2.97 × 10 5 and 1.25 × 10 5 ) were transformed into carbanilates (CTC) which were then fractionated by the elution method at a constant composition of the acetone‐water elution mixture with the column temperature gradually increasing from −30°C to 30°C, and by the GP…
Melting and degradation behaviour of needle‐like poly(oxymethylene) crystals
Abstract DSC/TG (differential scanning calorimetry/thermal gravimetry) simultaneous measurements have been carried out for needle‐like and other poly(oxymethylene) crystals and the occurrence of degradation, overlapping the melting, has been confirmed for needle‐like and fibrous extended‐chain crystals. A theory to an…
A compact formulation for the bond-polarizability theory of the Raman effect
A compact formulation for the computation of the Raman tensors of vibrating molecules as a function of bond polarizabilities is presented. This formulation is conceptually clearer than those given previously and also very convenient for the numerical computation of Raman intensities. The Raman tensors of the vibration…
Atomistic calculation of the core structure and Peierls energy of an (a/2) [110] edge dislocation in MgO
The core configuration and energies of the two symmetric configurations of an (a/2) [110] edge dislocation in a model MgO crystal were calculated atomistically using a point-ion or shell model with a rigid boundary region. Two short-range potentials and one set of shell-model parameters used in the present calculation…
The influence of crystal form on the radial stress transmission characteristics of pharmaceutical materials
Various crystal forms of sulphathiazole, barbitone and aspirin were compressed in a single-punch tablet machine instrumented to monitor axially applied and radially transmitted forces, and upper punch movement. The changes in radial stress during the compression cycle depended upon the polymorphic form of the compress…
Elastic scattering of 0.1-1-MeV photons
Theoretical values of Rayleigh scattering amplitudes for the $K$ shell and for higher atomic shells are calculated from the second-order $S$ matrix of quantum electrodynamics. The calculations are combined with nuclear Thomson scattering to predict elastic scattering differential cross sections for photon energies bet…