Structural and energetics effects in the chemical ionization of halogen-substituted benzenes and toluenes

1976 ◽  
Vol 54 (21) ◽  
pp. 3439-3452 ◽  
Author(s):  
Hei-Wun Leung ◽  
Alex G. Harrison
Keyword(s):  
Mass Spectra ◽  
Chemical Ionization ◽  
The Other ◽  
Substituted Benzenes ◽  
Fragment Ions ◽  
Other Hand ◽  
Benzyl Halides

The H2, D2, CH4, and CD4 chemical ionization (CI) mass spectra of XC6H5, C6H5CH2X, and XC6H4CH3 (X = Cl, Br, and I) have been determined. For the benzyl halides the dominant ion observed in all CI spectra is the m/q 91 (benzyl) ion formed by loss of HX(DX) from the protonated (deuteronated) molecule. The CI spectra of the isomeric halotoluenes differ substantially from the spectra of the benzyl halides indicating that isomerization to a common (tropylium-like) structure does not occur in CI. In the H2 CI of XC6H4Y (Y = H or CH3) the major fragment ions observed are YC6H5•H+, [Formula: see text], and YC6H4+, with the relative yields depending strongly on the halogen substituent. Neither the YC6H5•H+ ion, resulting from HX loss from the H3+•XC6H4Y complex, nor the YC6H4+ ion, resulting from HX loss from XC6H4Y•H+, are observed when X = I. On the other hand [Formula: see text], resulting from elimination of X• from XC6H4Y•H+, is observed only for X = Br and I. In the CH4 CI of XC6H4Y, in addition to XC6H4Y•H+ ions, CH3C6H4Y•H+ ions (HX loss from the CH5+•XC6H4Y complex) are observed for X = F and Cl, while [Formula: see text] ions (loss of X• from XC6H4Y•H+) are observed only when X = I. In addition, displacement of I• by C2H5+, and by C3H5+, is observed in the CH4 CI of the iodo-substituted compounds. The dependency of the products observed and their relative yields on the identity of the halogen substituent is discussed in relation to the reaction energetics.

Evaluation of nitric oxide chemical ionization mass spectra of substituted benzenes

1991 ◽  
Vol 26 (5) ◽  
pp. 486-492 ◽  
Author(s):  
Shigeki Daishima ◽  
Yoshio Lida ◽  
Fujihiro Kanda
Keyword(s):  
Nitric Oxide ◽  
Mass Spectra ◽  
Chemical Ionization ◽  
Ionization Mass ◽  
Substituted Benzenes

scholarly journals Charge transfer control by substituents: Donor pyrroles and fluoro-anilines

2005 ◽  
Vol 7 (3) ◽  
pp. 121-124 ◽  
Author(s):  
Antje Neubauer ◽  
Sukumaran Murali ◽  
Wolfgang Rettig
Keyword(s):  
Charge Transfer ◽  
Benzene Ring ◽  
The Other ◽  
Substituted Benzenes ◽  
Other Hand ◽  
Alkane Solvents ◽  
New Compounds ◽  
Derivatives Of ◽  
Acceptor Moiety ◽  
Donor Substituent

Derivatives of N-phenyl pyrrole with a para-donor substituent on the acceptor benzene ring are compared. It is shown that by a suitable increase of the donor strength of the pyrrolo group, CT fluorescence can be achieved even for donor-donor substituted benzenes. On the other hand, introducing fluoro substituents into the acceptor moiety strongly enhances the CT formation tendency, and several new compounds with CT fluorescence even in alkane solvents are presented.

scholarly journals Synthesis, Characterization and Antitumor Activity of Some New Oganotellurium Compounds Containing Azomethine Group, Part One

2016 ◽  
Vol 8 (1) ◽  
pp. 1464-1471 ◽  
Author(s):  
Rafid H. Al-Asadi ◽  
Tarik A. Fahad ◽  
Bahjat A. Saeed ◽  
Wasfi A. Al-Masoudi
Keyword(s):  
Antitumor Activity ◽  
Hydrazine Hydrate ◽  
Schiff Bases ◽  
Elemental Analysis ◽  
13C Nmr ◽  
Mass Spectra ◽  
The Other ◽  
Azomethine Group ◽  
Other Hand ◽  
Group Part

New tellurated schiff bases were synthesized by the reaction of the corresponding mercurated Schiff  bases compounds A1-A3 with tellurium tetrabromide in 1:1 mole ratio and  that  gave organyltellurium tribromides  A4-A6.  On the other hand, when mercurated schiff bases and tellurium tetrabromide brought  together in 2:1 mole ratio gave diorganyltellurium dibromides compounds A10-A12 followed by reduction with hydrazine hydrate gave new diorganyl tellurides A13-A15.  Reduction of compounds A4-A6 by  hydrazine hydrate gave new ditellurides A7-A9.  All compounds were characterized by elemental analysis, IR, 1H , 13C NMR, HSQC-NMR and mass spectra.  Invitro anti-tumor bioactivity of some compounds were tested. 

Analysis of Testosterone Esters by Tandem Mass Spectrometry

1993 ◽  
Vol 76 (2) ◽  
pp. 306-312 ◽  
Author(s):  
Thomas Cairns ◽  
Emil G Siegmund ◽  
Bobby Rader
Keyword(s):  
Mass Spectrometry ◽  
Tandem Mass Spectrometry ◽  
Relative Abundance ◽  
Mass Spectra ◽  
Chemical Ionization ◽  
Generic Product ◽  
Tandem Mass ◽  
Fragment Ions ◽  
Product Ions ◽  
The Individual

Abstract The electron ionization (El) and chemical ionization (CI) mass spectra of 12 representative testosterone esters were examined to explore the various analytical options available for identification and confirmation of the esters. Using El, a number of fragment ions indicated the identification of the testosterone moiety, but structural confirmation of the individual esters often required the observance of the molecular ion at very low relative abundance ratios. The acceptable analytical method involved CI/tandem mass spectrometry based on the production of the 2 generic product ions derived from the protonated molecule ion.

Mechanism and structure in chemical ionization mass spectrometry: tricyclic flavanoid compounds

1973 ◽  
Vol 26 (7) ◽  
pp. 1577 ◽  
Author(s):  
JW Clark-Lewis ◽  
CN Harwood ◽  
MJ Lacey ◽  
JS Shannon
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectra ◽  
Chemical Ionization ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Fragmentation Pathways ◽  
Fragment Ions ◽  
Metastable Ions ◽  
Fragmentation Patterns

The chemical ionization mass spectra of a series of tricyclic flavanoid compounds have been examined using isobutane and hydrogen as reagent gases and the fragmen- tation modes have been correlated systematically in terms of structure. The technique produces simple fragmentation patterns and abundant metastable ions. The use of deuterium as reagent gas reveals the influence of extraneous water on the spectra and facilitates the interpretation of the fragmentation pathways. The fragment ions appear to arise from isomeric progenitors protonated at different sites in the molecules.

Mass spectral studies of lanthanide chelates. I. Samarium, europium, gadolinium and terbium chelates of thenoyltrifluoroacetone

1975 ◽  
Vol 28 (7) ◽  
pp. 1513 ◽  
Author(s):  
M Das ◽  
SE Livingstone
Keyword(s):  
Mass Spectra ◽  
The Other ◽  
Spectral Studies ◽  
Mass Spectral ◽  
Lanthanide Chelates ◽  
Other Hand ◽  
Europium Chelates ◽  
Fragmentation Patterns ◽  
Terbium Chelates ◽  
Bivalent State

The mass spectra of the lanthanide chelates of thenoyltrifluoroacetone, viz. Met{CF3COCH=C(O-)-C4H3S}3 (Met = Sm, Eu, Gd, Tb), have been obtained. All four spectra display similar fragmentation patterns. Fluorine migration to the metal with the concomitant loss of :CF2 occurs with all four lanthanide chelates. Peaks were observed for the ions [MetF2]+ (Met = Sm, Gd, Tb) and [MetF]+ (Met = Sm, Eu). The occurrence of [MetF]+ in the spectra of the samarium and europium chelates is in keeping with the tendency of these two lanthanides to be reduced to the bivalent state. On the other hand, oxidation of terbium(III) to terbium(IV) was not observed in the mass spectra.

Photochemical and mass spectrometric transformation of gibberellenic acid to 9-epiallogibberic acid

1984 ◽  
Vol 62 (10) ◽  
pp. 1996-1998 ◽  
Author(s):  
Hussain K. Al-Ekabi ◽  
Ghazi A. W. Derwish
Keyword(s):  
Electron Impact ◽  
Mass Spectra ◽  
Mass Spectrometric ◽  
The Other ◽  
Positive Mass ◽  
Hydrogen Migration ◽  
Other Hand ◽  
Impact Fragmentation

Gibberellenic acid (2) reacted thermally in a modified immersion photochemical reactor, to give an intermediate triene (3). This triene then isomerized photochemically, via suprafacial [1,3]-hydrogen migration, to 9-epiallogibberic acid (5). On the other hand, comparison of the positive mass spectra of gibberellenic acid (2), allogibberic acid (4), and 9-epiallogibberic acid (5) showed that gibberellenic acid underwent electron impact fragmentation to the triene 3 cation. This cation then rearranged through suprafacial [1,3]-hydrogen migration to the 9-epiallogibberic acid (5) cation.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

Closing the GAP—A 5Å Scanning Microscope

1969 ◽  
Vol 27 ◽  
pp. 6-7
Author(s):  
A. V. Crewe
Keyword(s):  
Normal Form ◽  
The Other ◽  
Resolving Power ◽  
Scanning Microscope ◽  
Conventional Microscope ◽  
Other Hand ◽  
Closing The Gap ◽  
Thermal Sources ◽  
Better Than ◽  
Transmission Microscope

We have become accustomed to differentiating between the scanning microscope and the conventional transmission microscope according to the resolving power which the two instruments offer. The conventional microscope is capable of a point resolution of a few angstroms and line resolutions of periodic objects of about 1Å. On the other hand, the scanning microscope, in its normal form, is not ordinarily capable of a point resolution better than 100Å. Upon examining reasons for the 100Å limitation, it becomes clear that this is based more on tradition than reason, and in particular, it is a condition imposed upon the microscope by adherence to thermal sources of electrons.

Life Beyond 1MeV

1980 ◽  
Vol 38 ◽  
pp. 30-33
Author(s):  
K.H. Westmacott
Keyword(s):  
Electron Microscopy ◽  
Past Experience ◽  
The Other ◽  
Good Case ◽  
Other Hand ◽  
The U.S

Life beyond 1MeV – like life after 40 – is not too different unless one takes advantage of past experience and is receptive to new opportunities. At first glance, the returns on performing electron microscopy at voltages greater than 1MeV diminish rather rapidly as the curves which describe the well-known advantages of HVEM often tend towards saturation. However, in a country with a significant HVEM capability, a good case can be made for investing in instruments with a range of maximum accelerating voltages. In this regard, the 1.5MeV KRATOS HVEM being installed in Berkeley will complement the other 650KeV, 1MeV, and 1.2MeV instruments currently operating in the U.S. One other consideration suggests that 1.5MeV is an optimum voltage machine – Its additional advantages may be purchased for not much more than a 1MeV instrument. On the other hand, the 3MeV HVEM's which seem to be operated at 2MeV maximum, are much more expensive.

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