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Volume 42 (1994)
- Issue 6 Pages 291-
- Issue 5 Pages 249-
- Issue 4 Pages 225-
- Issue 3 Pages 155-
- Issue 2 Pages 67-
- Issue 1 Pages 1-
Volume 42, Issue 3
Displaying 1-5 of 5 articles from this issue
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REGULAR PAPERS
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Hisao NAKATA, Natsuko YAMAOKA, Kenji KADOGUCHI1994 Volume 42 Issue 3 Pages 155-163
Published: 1994
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSChemical ionization mass spectra of bifunctional o-xylylene amino hydroxy derivatives were measured and compared to those of m- or p-compounds. The intensity of [MH]+ peaks from o-compounds were larger than those from m- or p-isomers. This is due to the stabilization by internal hydrogen bond formation between two neighboring functional groups in stable and non-decomposing [MH]+ ions. The extent of fragmentation ratio of each functional group was calculated from observed relative intensities of respective fragment ion peaks. Surprisingly the ratio falls into approximately the same range of the corresponding ratio of m- or p-compounds. The results indicated that internal hydrogen bond formation, which may lead to proton transfer, could not compete with the simple bond cleavage in energy-rich fragmenting [MH]+ ions.View full abstractDownload PDF (605K) -
Takae TAKEUCHI, Naomi YONEZAKI, Masao YAMAMOTO1994 Volume 42 Issue 3 Pages 165-175
Published: 1994
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSThe fragmentations of six silaspiroalkanes combined with four-, five-, and six-membered rings in EI mass spectrometry have been studied by a B/E linked scanning technique and an ab initio MO method. The main fragmentation process from the molecular ion is the consecutive losses of two ethylene molecules which occur via the cleavage of an Si-C bond in each ring of silaspiroalkanes. From the ab initio MO calculation, we found that the initial bond fission occurred in an Si-C bond of the molecular ion. At that time, the cleavage of an Si-C bond occurs in the smaller ring more easily than in the larger one, since the strain on the smaller ring is larger. We found the metastable decomposition due to a CH3 loss from the molecular ions of 4-silaspiro[3.5]nonane, 5-silaspiro[4.4]nonane, and 4-silaspiro[3.4]octane.View full abstractDownload PDF (637K) -
Toshihide NISHIMURA1994 Volume 42 Issue 3 Pages 177-192
Published: 1994
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSCesium-beam gas-phase ionization (CBI) mass spectra measured for several organic molecules demonstrated a considerable fragmentation suggesting excitation energies in CBI higher than those in electron ionization (EI). A methodology to extract excitation energy distribution resulting from CBI has been developed using the knowledge of breakdown curves of product ions, and the energy deposition function (P) for the molecular ion prior to fragmentation has been experimentally evaluated using the well understood breakdown curves of hexacarbonyl chromium ions. It was found that energies of effective excitation are higher than 17 eV and the excitation probability decreases with decreasing the internal energy of the molecular ion (E). Additionally, these excitation energy distributions observed were not significantly influenced by the acceleration voltage of cesium beam. A plot of ln(P/E) against E showed a linear relationship with a positive slope although such the plot should result in a negative linearity for collision-induced dissociation processes. These results have here been interpreted not by collision excitation directly due to translational energy transfer caused by fast-atom bombardment but by a resonant ionization due to the formation of fast super-excited Rydberg cesium atoms attributed to an incomplete recombination of a fast Cs+ and an electron in a Cs-FAB source.View full abstractDownload PDF (829K) -
Mitsuo TAKAYAMA1994 Volume 42 Issue 3 Pages 193-206
Published: 1994
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSSuccessive neutral C2 losses from multiply-charged fullerene ions, C60z+ and C70z+ (z=1~4), have been examined using gas-phase fast particle bombardment (FPB) technique with He, Ar, and isobutane beams. Quadruply-charged ions, C604+ and (C60-C2n)4+ (n = 1~5), were detected by optimizing the experimental conditions. Smallest fragments originated from C2 losses from C60+·, C602+, C603+, and C604+ ions were C36+·, C422+, C443+, and C504+, respectively. The extents of C2 losses from C60z+ and C70z+ (z= 1~4) ions have been compared with each other, using gas-phase FPB and collision-induced dissociation techniques. Metastable peaks originated from C2 and/or C4 losses from C602+ ion were detected. On the basis of the results obtained, kinetics and energetics of C2 losses from C60 ions have been discussed, and the internal energy of C60+· ion produced under gas-phase FPB conditions was roughly estimated.View full abstractDownload PDF (727K) -
Yoshiyuki MOCHIDA, Yukio YOKOYAMA, Toshinaga KAWAI, Shigeo NAKAMURA, M ...1994 Volume 42 Issue 3 Pages 207-215
Published: 1994
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSA mixture of isomeric methyl 9-, 10-, 11-, and 12-hydroperoxyoleates was analyzed by liquid ionization (LI) mass spectrometry. LI mass spectra of the hydroperoxides exhibited [M+H]+ peaks clearly at m/z 329, while both chemical ionization and fast atom bombardment mass spectra did not show ions directly related to the molecular weight. The fragment peaks of the hydroperoxides observed at m/z 295, corresponding to the loss of H2O2 from [M+H]+, were useful to discriminate the hydroperoxides from structurally isomeric hydroxyepoxides. In addition, several characteristic fragments were observed at m/z 173, 187, 199, 201, and 213, which were also indicative of the position of the hydroperoxy group in the hydroperoxides.View full abstractDownload PDF (527K)
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