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001-es BibID:	BIBFORM095780
Első szerző:	Kéki Sándor (polimer kémikus)
Cím:	A simple method for estimating activation energies using the fragmentation yield: Collision-induced dissociation of iron(II)-phenanthroline complexes in an electrospray ionization mass spectrometer / Sandor Keki, Lajos Nagy, Janos Torok, Gyorgy Deak, Miklos Zsuga
Dátum:	2006
ISSN:	1044-0305
Megjegyzések:	The gas-phase stabilities of Fe(?){sub 3}{sup 2+} complexes, where ? represents the 1,10-phenanthroline, 5-chloro-1,10-phenanthroline, 5-methyl-1,10-phenanthroline, 3,4,7,8-tetramethyl-1,10-phenanthroline, and 4,7-diphenyl-1,10-phenanthroline ligands were investigated by collision-induced dissociation (CID) in the capillary-first skimmer region upon changing the voltage difference between the capillary and the skimmer. The loss of only one ligand from the Fe(?){sub 3}{sup 2+} complexes was observed with each of the phenanthroline ligands studied. An increase in the voltage difference between the capillary and the skimmer resulted in a higher fragmentation yield as calculated from the intensity of the precursor and the fragment ion. The fragmentation yield versus capillary-skimmer voltage difference plots were evaluated by means of the Arrhenius and the Rice-Ramsperger-Kassel (RRK) model by fitting the model parameters to the experimental data. Both models yielded practically the same results. In addition, if the internal energy gained through the capillary-skimmer region is estimated correctly, the approximate value of the critical energy (activation energy) for fragmentation can be extracted from the fragmentation yield versus capillary-skimmer voltage difference plots. It was found that the gas-phase stabilities of the Fe(?){sub 3}{sup 2+} complexes are nearly identical except for the more stable Fe(II)-4,7-diphenyl-1,10-phenanthroline complex. The critical energy for fragmentation was estimated to be ?1.2 and 0.9 eV for the Fe(II)-4,7-diphenyl-1,10-phenanthroline, and the other complexes, respectively.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban folyóiratcikk
Megjelenés:	Journal of The American Society For Mass Spectrometry. - 17 : 7 (2006), p. 962-966. -
További szerzők:	Nagy Lajos (1979-) (vegyész) Török János Deák György (1954-) (polimer kémikus) Zsuga Miklós (1944-) (polimer kémikus)
Pályázati támogatás:	T 037448 OTKA T 042740 OTKA M 28,369 OTKA M 36,872 OTKA MU-00,204/2001 OTKA
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001-es BibID:	BIBFORM005398
Első szerző:	Kéki Sándor (polimer kémikus)
Cím:	Atmospheric Pressure Photoionization Mass Spectrometry of Polyisobutylene Derivatives / Sándor Kéki, János Török, Lajos Nagy, Miklós Zsuga
Dátum:	2008
Megjegyzések:	A detailed atmospheric pressure photoionization mass spectrometric (APPI-MS) study on three types of polyisobutylene derivatives is reported. Two of the polyisobutylenes investigated were polyisobutylene with dihydroxy and diolefinic end-groups derived from aromatic moieties [dicumyl chloride, 1,4-bis(2-chloro-2-propyl)benzene], and the third contained no aromatic moieties with a monohydroxy end-group. All three polyisobutylene derivatives (PIBs) had an average molecular weight (Mn) of ?2000 g/mol, with a polydispersity lower than 1.2. The experimental setup allowed the study of the influence of the end-group and the initiator moiety on the APPI-MS properties of these polymers. In the positive ion APPI mode, protonated PIB molecules were formed, but the molecular weights obtained were considerably lower than those expected, indicating fragmentation of the PIB chains. In the negative APPI mode, using solvents such as tetrahydrofuran and toluene as dopants, no signal was obtained. However, in chlorinated solvents, such as CCl4, CHCl3 and CH2Cl2, in the presence of toluene dopant, PIB adducts with chloride ions were formed with relatively high signal intensity. In the case of CH2Cl2, no dopant (toluene) was necessary to generate chlorinated adduct ions, albeit increasing the toluene concentration in the flow increased the PIB signal intensity. The effect of the toluene concentration (at a fixed total flow rate) on PIB signal intensity was thoroughly studied and models that include (i) photoionization of toluene, (ii) formation of chloride ions from the chlorinated solvents by dissociative electron capture, (iii) formation of chlorinated adduct ions and charge recombination reactions between the toluene radical cation, (iv) chloride ions, and (v) chlorinated adduct ions are proposed based on the experimental results.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban Polyisobutylene APPI-MS mass spectrometry chloride ion attachment
Megjelenés:	Journal of the American Society for Mass Spectrometry. - 19 (2008), p. 656-665. -
További szerzők:	Török János Nagy Lajos (1979-) (vegyész) Zsuga Miklós (1944-) (polimer kémikus)
Internet cím:	DOI elektronikus változat
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001-es BibID:	BIBFORM001193
Első szerző:	Kéki Sándor (polimer kémikus)
Cím:	Energy-variable collision-induced dissociation study of 1,3,5-trisubstituted 2-pyrazolines by electrospray mass spectrometry / Sándor Kéki, Lajos Nagy, János Török, Katalin Tóth, Albert Lévai, Miklós Zsuga
Dátum:	2007
Megjegyzések:	The pathways of the ([M+H]+) ions generated from electrosprayed solutions of nine 1,3,5-trisubstituted 2-pyrazoline derivatives were studied using energy-variable collision-induced dissociation (CID) and pseudo-MS3 (in-source CID combined with MS/MS) methods. It was shown that under CID conditions several structurally important product ions such as the 2,4-substituted azete and 1,2-substituted aziridine ions were formed. The compositions of the product ions were unambiguously supported by accurate mass measurement (mass accuracy was within +/-8 ppm). The fragmentation pathways of 1,3,5-trisubstituted 2-pyrazolines were established by means of pseudo-MS3. It was found that a substituent at the N-1 position greatly affects the fragmentation pathways of the 2-pyrazoline derivatives. The 1-acetyl- and 1-propionyl-2-pyrazoline derivatives dissociate mainly through formation of a pyrazolium cation, while in the case of 1-phenyl-2-pyrazoline derivatives product ions arising from the consecutive fragmentation of 2,4-substituted azete and 1,2-substituted aziridine ions dominate. Another interesting finding is the formation of a radical cation from the 2,4-substituted azete by loss of a methyl radical. The fragmentation yield as a function of the collision energy for each of the 1,3,5-trisubstituted 2-pyrazolines was determined. Based on the fragmentation yield versus collision energy curves the relative fragmentation stabilities for the 1,3,5-trisubstituted 2-pyrazoline derivatives were also evaluated.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Rapid Communications in Mass Spectrometry. - 21 : 11 (2007), p. 1799-1808. -
További szerzők:	Nagy Lajos (1979-) (vegyész) Török János Tóth Katalin Zsuga Miklós (1944-) (polimer kémikus) Lévai Albert (1941-) (kémikus)
Internet cím:	DOI elektronikus változat
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