Search results for "Polyatomic ion"
showing 7 items of 47 documents
ChemInform Abstract: Mass Spectrometry of 3,4-Dihydroquinazolin-4-ones of Pharmaceutical Interest. Part 3. Electron Ionization Mass Spectra of 2-Subs…
2010
The fragmentation reactions induced by electron impact of eighteen title compounds has been investigated with the aid of low beam energy spectra (14 eV, nom. value), metastable ion detection, high resolution measurements and labelling experiments. The loss of the 4-carbonyl oxygen together with the 3-substituent, which constitutes a characteristic fragmentation route of 3-aryl and 3-heteroaromatic substituted-4(3H)-quinazolinones, is again observed, but the presence of a carboxyethyl group at the 4′-position of the pyrazole ring is responsible of an anomalous loss of 47 daltons from the molecular ion. Lastly, a comparison with the previously described behaviour of 3-(5′-isoxazolyl) derivati…
Mass spectrometry of 3,4-dihydroquinazolin-4-ones of pharmaceutical interest. Part3. Electron ionization mass spectra of 2-substituted-3-(5′-pyrazoly…
1992
The fragmentation reactions induced by electron impact of eighteen title compounds has been investigated with the aid of low beam energy spectra (14 eV, nom. value), metastable ion detection, high resolution measurements and labelling experiments. The loss of the 4-carbonyl oxygen together with the 3-substituent, which constitutes a characteristic fragmentation route of 3-aryl and 3-heteroaromatic substituted-4(3H)-quinazolinones, is again observed, but the presence of a carboxyethyl group at the 4′-position of the pyrazole ring is responsible of an anomalous loss of 47 daltons from the molecular ion. Lastly, a comparison with the previously described behaviour of 3-(5′-isoxazolyl) derivati…
Ferro- and Antiferromagnetic Interactions in Oxalato-Centered Inverse Hexanuclear and Chain Copper(II) Complexes with Pyrazole Derivatives.
2021
Two novel copper(II) complexes of formulas {[Cu(4-Hmpz)4][Cu(4-Hmpz)2(µ3-ox-κ2O1,O2:κO2′:κO1′)(ClO4)2]}n (1) and {[Cu(3,4,5-Htmpz)4]2[Cu(3,4,5-Htmpz)2(µ3-ox-κ2O1,O2:κO2′:κO1′)(H2O)(ClO4)]2[Cu2(3,4,5-Htmpz)4(µ-ox-κ2O1,O2:κ2O2′,O1′)]}(ClO4)4·6H2O (2) have been obtained by using 4-methyl-1H-pyrazole (4-Hmpz) and 3,4,5-trimethyl-1H-pyrazole (3,4,5-Htmpz) as terminal ligands and oxalate (ox) as the polyatomic inverse coordination center. The crystal structure of 1 consists of perchlorate counteranions and cationic copper(II) chains with alternating bis(pyrazole)(µ3-κ2O1,O2:κO2′:κO1′-oxalato)copper(II) and tetrakis(pyrazole)copper(II) fragments. The crystal structure of 2 is made up of perchlorat…
Gas phase behavior of radical cations of perfluoroalkyl-1,2,4-triazines: an experimental and theoretical study
2009
Electron ionization mass spectrometry and low-energy collision-induced decomposition reactions occurring in a tridimensional ion trap, together with density functional theory (DFT) calculations on neutrals, even- and odd-electron cations, have been used to study the gas-phase ion chemistry of a series of perfluoroalkyl-1,2,4-triazines. Loss of oxygen, due to thermal degradation occurring before ionization, likely involving the hydroxylamino group, has been observed. Compounds having a carbonyl group at position 6 of the triazine ring fragment in the source by elimination of NO followed by HF or CO. The decomposition pathways occurring due to CID experiments have shown interesting features d…
A new general fragmentation reaction in mass spectrometry: The hydrogen-carbon, carbon-carbon double rearrangement of 2 heteroalkyl substituted diphe…
1995
Diphenylmethyl cations formed by benzylic cleavage of the molecular ions of ortho heteroalkyl substituted 1,1-diphenylalkanes undergo the double rearrangement process (H to C followed by C to C) previously reported for ortho-methoxy derivatives. Hence the formation of substituted benzyl (or tropylium) ions allowing this double rearrangement process constitutes an interesting type of fragmentation reaction characteristic for 1,1-diphenylalkanes bearing ortho substituents (OMe, OEt, OiPr, SMe, NHMe, NMe2) which are able to transfer a hydride to the charged benzyl carbon of diphenylmethyl cations formed by benzylic cleavage of the molecular ion.
Resonance in Interacting Induced-Dipole Polarizing Force Fields: Application to Force-Field Derivatives
2009
The Silberstein model of the molecular polarizability of diatomic molecules, generalized by Applequist et al. for polyatomic molecules, is analyzed. The atoms are regarded as isotropically polarizable points located at their nuclei, interacting via the fields of their induced dipoles. The use of additive values for atom polarizabilities gives poor results, in some cases leading to artificial predictions of absorption bands. The molecular polarizability of methane and its derivative are computed. The agreement with experimental mean molecular polarizabilities is within 1–5%. A hypothesis is indispensable for a suitable representation of polarizability derivative.
Studies in organic mass spectrometry. Part 23. Role of the aroyl group on the competitive fragmentation reactions of the molecular ion of aroylanilid…
1999
The 70 eV and mass-analysed ion kinetic energy (MIKE) spectra of some thiophenecarboxanilides and benzoylanilides (1–10) have been compared in order to investigate the role of the aroyl (or heteroaroyl) moiety on the abundance of the competitive fragmentation reactions occurring in their molecular ions (amide–bond cleavage and phenol radical ion formation). It has been shown that the electron ionisation induced decompositions with high (70 eV) and low (MIKE) internal energy excess are qualitatively similar, but remarkable quantitative differences have been observed that can be accounted for in terms of the different effectiveness in the transmission of electronic effects of substituents in …