Diiodo Acetals and Unsaturated Lactones From Dihydropyran

1993 ◽  
Vol 46 (2) ◽  
pp. 203 ◽  
Author(s):  
MJ Lynch ◽  
J Simpson ◽  
RT Weavers
Keyword(s):  
Free Radical ◽  
X Ray ◽  
Ester Formation ◽  
Propiolic Acid ◽  
Unsaturated Lactones ◽  
By Products

Reaction of dihydropyran with propiolic acid and N- iodosuccinimide gave an iodo ester which was cyclized under free-radical conditions to form an (E) iodomethylene lactone. Photolysis of this lactone could be controlled to generate mixtures of (E) and (Z) iodomethylene lactones, or alternatively the iodine-free methylene lactone. The structures of some by-products of the iodo ester formation have been shown to be a succinimide derivative and two stereoisomers of a diiodo acetal. X-Ray determination of the structure of one of the diiodo acetal isomers is described.

A Curious By-Product in the Tipson-Cohen Reaction of a Carbohydrate Ditosylate

1990 ◽  
Vol 43 (6) ◽  
pp. 1111 ◽  
Author(s):  
LM Engelhardt ◽  
M Mocerino ◽  
RV Stick ◽  
AH White
Keyword(s):  
Single Crystal ◽  
Structure Determination ◽  
X Ray ◽  
By Products

The treatment of methyl 4,6-O-benzylidene-2,3-di-O-p-toluenesulfony-β- D- galactoside , methyl 4,6-O-benzylidene-3-O-benzenesulfonyl-2-O-p- toluenesufonyl-β-D-galactoside and methyl 4,6-O-benzylidene-2-O- benzenesulfonyl-3-O-p-touenesulfonyl-β-D-galactoside under Tipson-Cohen conditions (Zn/ Nal/dimethylformamide ) gives mainly the alkene, methyl 4,6-O-benzylidene-2,3-dideoxy-β-D-threo-hex-2-enoside. However, the first two glycosides give methyl 4,6-O-benzylidene-3-deoxy-3-C-(m-methylphenyl )-β-D- galactoside, and the last, methyl 4,6-O-benzylidene- 3-deoxy-3-C-phenyl-β-D-gaactoside, as minor by-products resulting from a curious reaction of the supposed iodo sulfonate intermediate. The structure of methyl 4,6-O-benzylidene-3-deoxy-3-C-(m- methylphenyl )-β-D- galactoside was confirmed by a single-crystal X-ray structure determination of the derived p-bromobenzoate.

Application of X-Ray-Fluorescence Spectrometry to the Analysis of Ta-Nb-Sn Slags and Associated By-Products

1987 ◽  
Vol 41 (3) ◽  
pp. 509-512 ◽  
Author(s):  
A. M. E. Balaes ◽  
K. Dixon ◽  
G. J. Wall
Keyword(s):  
Computer Program ◽  
Analytical Procedure ◽  
Influence Factor ◽  
Matrix Effects ◽  
Fluorescence Spectrometry ◽  
Solid Materials ◽  
X Ray ◽  
Residual Matrix ◽  
By Products

This paper describes the development of an accurate, precise, and rapid analytical procedure using x-ray-fluorescence spectrometry for the determination of Nb, Ta, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe, Zr, and Sn in a wide variety of materials resulting from the processing of Ta-Nb-Sn slags to produce Ta-Nb oxides. The method involves evaporation of all the liquids to dryness, a 1:8 fusion of the solid materials with a flux consisting of Na-Li tetraborate and Na2CO3, and the addition of La oxide as a heavy absorber. With the use of a computer program, residual matrix effects are corrected for by influence-factor calculations.

Heterocyclic Compounds from Alloxan and Amines. XIV. Structure of Even-Electron Products Derived from Free-Radical Betaines

1979 ◽  
Vol 32 (9) ◽  
pp. 1943 ◽  
Author(s):  
JW Clark-Lewis ◽  
MR Taylor ◽  
J Westphalen
Keyword(s):  
Free Radical ◽  
Least Squares ◽  
Heterocyclic Compounds ◽  
Full Matrix ◽  
X Ray ◽  
Dimer Structure

X-ray crystallographic determination of structure has shown that the even-electron product obtained thermally from 5-(10-phenyl-5,10-dihydro-5-phenazinioyl)-1,3-dimethyl-4-barbiturate (1) (e.g. by heating in benzene) has the structure 1,3-dimethy1-5-(10-phenyl-2,10-dihydrophenazin-2-ylidene)- hexahydropyrimidine-2,4,6-trione (3) instead of the previously supposed dehydro dimer structure (2). Crystals of compound (3) are triclinic, Pī, a 11�014(3), b 9�343(3), c 10�927(3) �, α 110�47(4), β 64�99(4), γ 101�47(4)�, Z = 2. Full-matrix least-squares refinement gave R 0�09. The rearrangement that occurs in the conversion of the free-radical betaine (1) into the trione (3) is a novel type of N to p-aromatic rearrangement which presumably entails dissociation followed by recombination and oxidation.

X-Ray Fluorescence Analysis of Ferrophosphorus and Slag from the Electric-Reduction Furnace Manufacture of Elemental Phosphorus

1970 ◽  
Vol 24 (2) ◽  
pp. 247-249 ◽  
Author(s):  
F. M. Yelinek ◽  
A. J. Graffeo ◽  
R. L. Carroll
Keyword(s):  
Chemical Analysis ◽  
Electric Furnace ◽  
Phosphate Rock ◽  
Production Control ◽  
Fluorescence Analysis ◽  
Elemental Phosphorus ◽  
X Ray ◽  
Reduction Furnace ◽  
By Products

X-ray fluorescence analysis has been applied to the determination of Si, P, and Fe in the ferrophosphorus and slag which are by-products in the manufacture of elemental phosphorus by reduction of phosphate rock in the electric furnace. Accuracy comparable to chemical analysis is obtained in a considerably shorter time, a factor important in production control.

Lateral resolution of the electron microbeam analysis

1978 ◽  
Vol 36 (1) ◽  
pp. 542-543
Author(s):  
H.J. Dudek
Keyword(s):  
Quantitative Analysis ◽  
Depth Resolution ◽  
Lateral Resolution ◽  
Cylindrical Particle ◽  
Correction Procedure ◽  
X Ray ◽  
Element Concentrations ◽  
Microbeam Analysis ◽  
The Matrix

The chemical inhomogenities in modern materials such as fibers, phases and inclusions, often have diameters in the region of one micrometer. Using electron microbeam analysis for the determination of the element concentrations one has to know the smallest possible diameter of such regions for a given accuracy of the quantitative analysis.In th is paper the correction procedure for the quantitative electron microbeam analysis is extended to a spacial problem to determine the smallest possible measurements of a cylindrical particle P of high D (depth resolution) and diameter L (lateral resolution) embeded in a matrix M and which has to be analysed quantitative with the accuracy q. The mathematical accounts lead to the following form of the characteristic x-ray intens ity of the element i of a particle P embeded in the matrix M in relation to the intensity of a standard S

Sem and X-Ray Analysis of Renal and Biliary Calculi

1976 ◽  
Vol 34 ◽  
pp. 306-307
Author(s):  
R. J. Narconis ◽  
G. L. Johnson
Keyword(s):  
Chemical Constituents ◽  
Natural State ◽  
X Ray Diffraction ◽  
Chemical Methods ◽  
X Ray ◽  
Additional Dimension ◽  
Biliary Calculi ◽  
Calculus Formation ◽  
Scanning Electron

Analysis of the constituents of renal and biliary calculi may be of help in the management of patients with calculous disease. Several methods of analysis are available for identifying these constituents. Most common are chemical methods, optical crystallography, x-ray diffraction, and infrared spectroscopy. The application of a SEM with x-ray analysis capabilities should be considered as an additional alternative.A scanning electron microscope equipped with an x-ray “mapping” attachment offers an additional dimension in its ability to locate elemental constituents geographically, and thus, provide a clue in determination of possible metabolic etiology in calculus formation. The ability of this method to give an undisturbed view of adjacent layers of elements in their natural state is of advantage in determining the sequence of formation of subsequent layers of chemical constituents.

Preparation And elemental analysis of ancient fibers

1987 ◽  
Vol 45 ◽  
pp. 410-411
Author(s):  
Allen Angel ◽  
Kathryn A. Jakes
Keyword(s):  
Cross Sections ◽  
Physical Structure ◽  
Energy Dispersive ◽  
Archaeological Sites ◽  
X Ray ◽  
Long Term Storage ◽  
Backscattered Electron ◽  
Electron Imaging

Fabrics recovered from archaeological sites often are so badly degraded that fiber identification based on physical morphology is difficult. Although diagenetic changes may be viewed as destructive to factors necessary for the discernment of fiber information, changes occurring during any stage of a fiber's lifetime leave a record within the fiber's chemical and physical structure. These alterations may offer valuable clues to understanding the conditions of the fiber's growth, fiber preparation and fabric processing technology and conditions of burial or long term storage (1).Energy dispersive spectrometry has been reported to be suitable for determination of mordant treatment on historic fibers (2,3) and has been used to characterize metal wrapping of combination yarns (4,5). In this study, a technique is developed which provides fractured cross sections of fibers for x-ray analysis and elemental mapping. In addition, backscattered electron imaging (BSI) and energy dispersive x-ray microanalysis (EDS) are utilized to correlate elements to their distribution in fibers.

Determination of Stoichiometry of GaAs Component in (Gaas)Ge Epitaxially Grown Thin Films by Electron Microprobe X-Ray Analysis

1990 ◽  
Vol 48 (2) ◽  
pp. 264-265
Author(s):  
D. R. Liu ◽  
S. S. Shinozaki ◽  
R. J. Baird
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Compound Semiconductors ◽  
Energy Dispersive Analysis ◽  
X Ray ◽  
Metastable Alloys ◽  
Lower Voltage

The epitaxially grown (GaAs)Ge thin film has been arousing much interest because it is one of metastable alloys of III-V compound semiconductors with germanium and a possible candidate in optoelectronic applications. It is important to be able to accurately determine the composition of the film, particularly whether or not the GaAs component is in stoichiometry, but x-ray energy dispersive analysis (EDS) cannot meet this need. The thickness of the film is usually about 0.5-1.5 μm. If Kα peaks are used for quantification, the accelerating voltage must be more than 10 kV in order for these peaks to be excited. Under this voltage, the generation depth of x-ray photons approaches 1 μm, as evidenced by a Monte Carlo simulation and actual x-ray intensity measurement as discussed below. If a lower voltage is used to reduce the generation depth, their L peaks have to be used. But these L peaks actually are merged as one big hump simply because the atomic numbers of these three elements are relatively small and close together, and the EDS energy resolution is limited.

Polarity Determination in Sphalerite and Wurtzite Structures

1990 ◽  
Vol 48 (2) ◽  
pp. 500-501
Author(s):  
Stuart McKernan ◽  
C. Barry Carter
Keyword(s):  
Opposite Polarity ◽  
Single Domain ◽  
Polar Material ◽  
Electron Microscopic ◽  
Dynamical Interaction ◽  
X Ray ◽  
Polarity Determination ◽  
The Absolute ◽  
Microscopic Techniques

The determination of the absolute polarity of a polar material is often crucial to the understanding of the defects which occur in such materials. Several methods exist by which this determination may be performed. In bulk, single-domain specimens, macroscopic techniques may be used, such as the different etching behavior, using the appropriate etchant, of surfaces with opposite polarity. X-ray measurements under conditions where Friedel’s law (which means that the intensity of reflections from planes of opposite polarity are indistinguishable) breaks down can also be used to determine the absolute polarity of bulk, single-domain specimens. On the microscopic scale, and particularly where antiphase boundaries (APBs), which separate regions of opposite polarity exist, electron microscopic techniques must be employed. Two techniques are commonly practised; the first [1], involves the dynamical interaction of hoLz lines which interfere constructively or destructively with the zero order reflection, depending on the crystal polarity. The crystal polarity can therefore be directly deduced from the relative intensity of these interactions.

Problems in Thin-Film X-ray Quantification

1990 ◽  
Vol 48 (2) ◽  
pp. 458-459
Author(s):  
J N Chapman ◽  
W A P Nicholson
Keyword(s):  
Thin Film ◽  
Specimen Thickness ◽  
X Rays ◽  
Characteristic Peak ◽  
Local Composition ◽  
X Ray ◽  
Measured Ratio ◽  
Path Lengths ◽  
Composition Changes

Energy dispersive x-ray microanalysis (EDX) is widely used for the quantitative determination of local composition in thin film specimens. Extraction of quantitative data is usually accomplished by relating the ratio of the number of atoms of two species A and B in the volume excited by the electron beam (nA/nB) to the corresponding ratio of detected characteristic photons (NA/NB) through the use of a k-factor. This leads to an expression of the form nA/nB = kAB NA/NB where kAB is a measure of the relative efficiency with which x-rays are generated and detected from the two species.Errors in thin film x-ray quantification can arise from uncertainties in both NA/NB and kAB. In addition to the inevitable statistical errors, particularly severe problems arise in accurately determining the former if (i) mass loss occurs during spectrum acquisition so that the composition changes as irradiation proceeds, (ii) the characteristic peak from one of the minority components of interest is overlapped by the much larger peak from a majority component, (iii) the measured ratio varies significantly with specimen thickness as a result of electron channeling, or (iv) varying absorption corrections are required due to photons generated at different points having to traverse different path lengths through specimens of irregular and unknown topography on their way to the detector.

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