ChemInform Abstract: THE FORMATION AND FRAGMENTATION OF NEGATIVE IONS DERIVED FROM ORGANIC MOLECULES

1985 ◽  
Vol 16 (1) ◽  
Author(s):  
J. H. BOWIE
Keyword(s):  
Organic Molecules ◽  
Negative Ions

Negative Ion Mass Spectra of Some Pesticidal Compounds

1971 ◽  
Vol 54 (6) ◽  
pp. 1340-1348 ◽  
Author(s):  
Peter C Rankin
Keyword(s):  
Organic Chemistry ◽  
Structural Analysis ◽  
Characteristic Feature ◽  
Mass Spectra ◽  
Organic Molecules ◽  
Negative Ions ◽  
Negative Ion ◽  
Carbamate Pesticides ◽  
Complex Organic

Abstract A study of the negative ion mass spectra of a number of complex organic molecules (pesticides) was undertaken to determine what information this technique would yield for structural analysis. The simplicity of the negative ion mass spectra was a characteristic feature and the most abundant negative ions in the spectra were assumed to be similar to the stable carbanions postulated in classical organic chemistry. The simplicity of the mass spectra suggested a possible application of the technique to the identification of carbamate pesticides.

Concluding remarks

1979 ◽  
Vol 293 (1400) ◽  
pp. 167-168
Keyword(s):  
Mass Spectrometry ◽  
High Pressure ◽  
Mass Spectrometer ◽  
Organic Molecules ◽  
Negative Ions ◽  
Negative Ion ◽  
Current Status ◽  
Source Analysis ◽  
Biological Chemistry ◽  
Mass Spectrometers

It is good that from time to time, a group of leading workers in a field should come together to discuss the current status of their research, and the direction in which it will most probably develop. We should all be grateful to the Royal Society in acting as hosts to this conference and to Professor Johnson and Professor Beynon for organizing it. I think that all will agree that the high quality of the papers presented have made this occasion a very memorable and valuable one. I should also like to thank the organizers for the relaxed atmosphere of the Conference, which made it so enjoyable. The last decade has seen a tremendous growth in both the instrumentation and techniques of mass spectrometry and the applications of mass spectrometry to organic and biological chemistry. On the instrumentation side, the modification of a double focusing mass spectrometer to yield ion kinetic energy spectra, giving information about the progenitors of a given ion, and the reversed geometry instrument, yielding information as to the daughter ions of a given parent, have both considerably contributed to our knowledge of the fragmentation of organic molecules. Again the development of special sources, field ionization and field desorption, the linking of a gas or high pressure liquid chromatograph to a mass spectrometer, and the introduction of high pressure sources for chemical ionization, have all made important contributions to organic and biological chemistry. The study of negative ions has also shed considerable light on the structure of organic molecules. Finally, the linking of computers with mass spectrometers has enabled results to be obtained very much more rapidly than in the past, and also made possible library searches to identify the substances present. Mr Craig discussed recent modifications in the source, analysis systems and detector systems of commercial mass spectrometers. Of particular importance was the increased sensitivity obtained by more effective ion collection. Among the newer techniques described during the meeting were g.c.-m.s. (Professor Jellum, Professor Jackson, Dr Morris, Professor Brooks and Professor Eglinton), collisional activation (Professor McLafferty and Dr Morris), negative ion mass spectrometry (Professor Jennings) and reversed geometry mass spectrometry (Professor Beynon).

The electron affinity of tetracyanoethylene and other organic electron acceptors

1976 ◽  
Vol 29 (9) ◽  
pp. 1919 ◽  
Author(s):  
LE Lyons ◽  
LD Palmer
Keyword(s):  
Electron Affinity ◽  
Organic Molecules ◽  
Threshold Energy ◽  
Negative Ions ◽  
Surface Ionization ◽  
Electron Affinities ◽  
Strong Electron ◽  
A Value ◽  
Organic Electron ◽  
Relative Electron

Information on the molecular structure of tetracyanoethylene and its mononegative ion is used to derive the electron affinity of tetracyanoethylene from the experimentally determined threshold energy for photodetachment of electrons from the negative ions. The resultant electron affinity of 2.3(� 0.3) eV is 0.6(� 0.4) eV less than a value derived by the magnetron surface ionization technique. Relative electron affinities for the strong electron acceptor organic molecules, which are known from charge-transfer spectra, are placed on an absolute scale using the photodetachment result for tetracyanoethylene.

High Resolution Replication of Organoclay Surfaces

1982 ◽  
Vol 40 ◽  
pp. 576-577
Author(s):  
W. W. Barker ◽  
W. E. Rigsby ◽  
V. J. Hurst ◽  
W. J. Humphreys
Keyword(s):  
Clay Mineral ◽  
Organic Molecule ◽  
Organic Molecules ◽  
X Ray Diffraction ◽  
Xrd Pattern ◽  
X Ray ◽  
Naturally Occurring ◽  
Silicate Layers ◽  
Mineral Identification

Experimental clay mineral-organic molecule complexes long have been known and some of them have been extensively studied by X-ray diffraction methods. The organic molecules are adsorbed onto the surfaces of the clay minerals, or intercalated between the silicate layers. Natural organo-clays also are widely recognized but generally have not been well characterized. Widely used techniques for clay mineral identification involve treatment of the sample with H2 O2 or other oxidant to destroy any associated organics. This generally simplifies and intensifies the XRD pattern of the clay residue, but helps little with the characterization of the original organoclay. Adequate techniques for the direct observation of synthetic and naturally occurring organoclays are yet to be developed.

Direct phase determination in electron crystallography: small organic molecules

1992 ◽  
Vol 50 (2) ◽  
pp. 1166-1167
Author(s):  
Douglas L. Dorset
Keyword(s):  
Organic Molecules ◽  
Data Sets ◽  
Temperature Structure ◽  
3D Analysis ◽  
Intensity Data ◽  
Electron Crystallography ◽  
Phase Determination ◽  
Measured Intensity ◽  
3D Data

The quantitative use of electron diffraction intensity data for the determination of crystal structures represents the pioneering achievement in the electron crystallography of organic molecules, an effort largely begun by B. K. Vainshtein and his co-workers. However, despite numerous representative structure analyses yielding results consistent with X-ray determination, this entire effort was viewed with considerable mistrust by many crystallographers. This was no doubt due to the rather high crystallographic R-factors reported for some structures and, more importantly, the failure to convince many skeptics that the measured intensity data were adequate for ab initio structure determinations.We have recently demonstrated the utility of these data sets for structure analyses by direct phase determination based on the probabilistic estimate of three- and four-phase structure invariant sums. Examples include the structure of diketopiperazine using Vainshtein's 3D data, a similar 3D analysis of the room temperature structure of thiourea, and a zonal determination of the urea structure, the latter also based on data collected by the Moscow group.

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