ChemInform Abstract: INTERACTION BETWEEN REMOTE BRIDGEHEAD SUBSTITUENTS IN 1,6-BIS-(1-CYANO-1-METHYL-ETHYL)TRIPTYCENES UNDER ELECTRON IMPACT

The constitutions of the cyclopolyarsines (AsR)n (R = methyl, ethyl, n-propyl, and phenyl) have been investigated by nuclear magnetic resonance and mass spectrometric techniques. A systematic study of their fragmentation under electron impact at different ionization potentials has confirmed the presence of pentameric alkyl and hexameric phenyl cyclic arsines. Variable temperature N.M.R. spectra obtained for pentamethylcyclopentaarsine have been interpreted in terms of a rapid pseudorotation process. Some mixed methylphenyl cyclic arsines have been identified.

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Electron-Impact Mass-Spectra of 3-Alkyl-2,1-benzisoxazoles

Australian Journal of Chemistry ◽

10.1071/ch9910863 ◽

1991 ◽

Vol 44 (6) ◽

pp. 863 ◽

Cited By ~ 3

Author(s):

LK Dyall ◽

JA Ferguson

Keyword(s):

Electron Impact ◽

Mass Spectra ◽

Methyl Ethyl ◽

Molecular Ion ◽

Partial Decomposition ◽

Methyl Cyanide ◽

Alkyl Groups ◽

Alkyl Cations ◽

Electron Impact Mass ◽

Impact Mass

3-Alkyl-2,1-benzisoxazoles underwent complex fragmentations under electron impact, and the balance between available pathways changed considerably across the range of alkyl groups (methyl, ethyl, isopropyl and t-butyl). The primary loss of CO is accounted for in terms of rearrangement of the initial molecular ion to an alkylimine ketene species. The 3-methyl compounds lost methyl as methyl cyanide, acylium cation or ketene, but the higher alkyl groups were chiefly lost as alkyl cations or by internal fragmentations in which some novel ortho-effects were noted. Most of these pathways were confirmed by B/E linked scans, and useful comparisons were made with the e.i . spectra of N- alkylanthranilic acids. All of these isoxazoles underwent partial decomposition on the heated probe.

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The Use of Styrenes as Embedding Media for Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100066498 ◽

1971 ◽

Vol 29 ◽

pp. 488-489

Author(s):

Edward D. De-Lamater ◽

Eric Johnson ◽

Thad Schoen ◽

Cecil Whitaker

Keyword(s):

Electron Microscopy ◽

Surface Tension ◽

Ultraviolet Light ◽

Methyl Ethyl Ketone Peroxide ◽

Methyl Ethyl ◽

Styrene Polymerization ◽

Radical Initiation ◽

Tertiary Butyl ◽

Low Viscosity ◽

Free Radical Initiation

Monomeric styrenes are demonstrated as excellent embedding media for electron microscopy. Monomeric styrene has extremely low viscosity and low surface tension (less than 1) affording extremely rapid penetration into the specimen. Spurr's Medium based on ERL-4206 (J.Ultra. Research 26, 31-43, 1969) is viscous, requiring gradual infiltration with increasing concentrations. Styrenes are soluble in alcohol and acetone thus fitting well into the usual dehydration procedures. Infiltration with styrene may be done directly following complete dehydration without dilution.Monomeric styrenes are usually inhibited from polymerization by a catechol, in this case, tertiary butyl catechol. Styrene polymerization is activated by Methyl Ethyl Ketone peroxide, a liquid, and probably acts by overcoming the inhibition of the catechol, acting as a source of free radical initiation.Polymerization is carried out either by a temperature of 60°C. or under ultraviolet light with wave lengths of 3400-4000 Engstroms; polymerization stops on removal from the ultraviolet light or heat and is therefore controlled by the length of exposure.

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The measurement of inner-shell ionization cross aections by electron impact in a TEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100130961 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1266-1267

Author(s):

Raynald Gauvin ◽

Gilles L'Espérance

Keyword(s):

Electron Impact ◽

Cross Sections ◽

Weight Fraction ◽

Thin Foil ◽

Specimen Thickness ◽

Ionization Cross ◽

Electron Dose ◽

Total Electron ◽

Inner Shell Ionization ◽

Shell Ionization

Values of cross sections for ionization of inner-shell electrons by electron impact are required for electron probe microanalysis, Auger-electron spectroscopy and electron energy-loss spectroscopy. In this work, the results of the measurement of inner-shell ionization cross-sections by electron impact, Q, in a TEM are presented for the K shell.The measurement of QNi has been performed at 120 KeV in a TEM by measuring the net X-ray intensity of the Kα line of Ni, INi, which is related to QNi by the relation :(1)where i is the total electron dose, (Ω/4π)is the fractional solid angle, ω is the fluorescence yield, α is the relative intensity factor, ε is the Si (Li) detector efficiency, A is the atomic weight, ρ is the sample density, No is Avogadro's number, t' is the distance traveled by the electrons in the specimen which is equal to τ sec θ neglecting beam broadening where τ is the specimen thickness and θ is the angle between the electron beam and the normal of the thin foil and CNi is the weight fraction of Ni.

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