Search results for " ionization"
showing 10 items of 621 documents
Spectrum emitted by a trapped electron
2007
We study the behaviour of a homonuclear molecule driven by an intense laser field. Newton's laws are used to describe the dynamics of nuclei while the quantal approach is reserved to the study of the electron. It is observed that the nuclei can oscillate or dissociate according to the degree of ionization of the molecule. In case of low ionization rate it is shown that great amount of information can be obtained by using the simplified approaches of fixed nuclei and of two-state approximation. Under suitable conditions the electron wave function spends a long time localized around one nucleus. The harmonic generation of the molecule is studied and seen to contain even harmonics.
Recognition of Li+ by a Salophen−UO2 Homodimeric Complex
2009
Self-assembly via mutual U-coordination of the salophen-UO(2) complex 1 creates a dimeric species which is shown to be useful for metal binding. Indeed, the 1 dimer has affinity for alkali metal cations and, interestingly, a marked selectivity for Li(+), determined by electrospray ionization mass spectrometry and (1)H NMR techniques. X-ray diffraction helped in the elucidation of the dimeric complex structure, which presents a crown-ether-type coordination site, in analogy to the more familiar 12-crown-4, responsible for the metal interaction. Comparison with isomer 2, and the salen derivative 3, increases the understanding of the behavior of such systems in solution and in the solid state.
Triple bridged μ-phenoxo-bis(μ-carboxylate) and double bridged μ-phenoxo-μ1,1-azide/μ-methoxide dicopper(II) complexes: Syntheses, structures, magnet…
2013
Abstract The work in this paper presents syntheses, characterization, crystal structures, catecholase activity, electrospray ionization mass spectroscopy (ESI-MS positive), and magnetic properties of seven triple bridged μ-phenoxo-bis(μ-carboxylate) dicopper(II) complexes [CuII2L(μ-HCOO)2](ClO4)·CH3OH (1), [CuII2L(μ-CH3COO)2](ClO4) (2), [CuII2L(μ-CCl3COO)2(H2O)](ClO4) (3), [CuII2L(μ-CH3CH2COO)2](ClO4) (4), [CuII2L(μ-CH3CH2CH2COO)2](ClO4) (5), [CuII2L(μ-PhCOO)2](ClO4)·CH3CN (6) and [CuII2L(μ-o-ClPhCOO)2](ClO4) (7), one double bridged μ-phenoxo-μ1,1-azide system [CuII2L(μ1,1-N3)(N3)2] (8) and one double bridged μ-phenoxo-μ-methoxide system [CuII2L(μ-OCH3)(NCO)2] (9), derived from a new dinucl…
Mass spectra of methoxychlorobenzenes (chloroanisoles)
1988
Electron impact mass of all 19 ring-substituted chloroanisoles have been investigated. The fragmentation pathways were elucidated with the aid of the 1st field-free region metastable ions. The greatest disparity between the spectra of the positional isomers is shown with the [M−CH 3 ] + and [M−CH 2 O] +• ions, i.e., the ortho and para isomers preferentially lose • CH 3 , whereas the meta isomers generally show both loss of • CH 3 and elimination of formaldehyde, the latter process being more dominant with the meta-monochloro and di- and trichloro isomers having two meta-chlorine atoms. Characteristic for all isomers is also the abundant M +• and [M−CH 3 −CO] + ions, the other fragmentation …
Diphenyltin(IV) complexes of the 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-olates: Synthesis and multinuclear NMR, 119Sn Mössbauer, electrospray ionizati…
2006
Abstract A series of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}diphenyltin(IV) complexes have been synthesized and characterized by 1H, 13C, 119Sn NMR, ESI-MS, IR and 119mSn Mossbauer spectroscopic techniques in combination with elemental analysis. The structures of a ligand L6H (i.e., 5-[(E)-2-(4-ethoxyphenyl)-1-diazenyl]quinolin-8-ol) and three diphenyltin(IV) complexes, viz., Ph2Sn(L1)2 · (CH3)2CO (1), Ph2Sn(L4)2 (4) and Ph2Sn(L5)2 (5) (L = 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-ol: aryl = phenyl – (L1H); 4′-methylphenyl – (L4H) and 4′-bromophenyl – (L5H)) were determined by single crystal X-ray diffraction. In general, the complexes were found to adopt a distorted cis-octahedral a…
Mass spectra of halogenated esters. Part IX—methyl esters of 2-butenoic acids containing chlorine and/or bromine atom(s)
1990
The electron impact mass spectra of methyl esters of chloro-, bromo-, dichloro-, bromochloro- and dibromo-2-butenoic acids (13 esters at all) have been investigated. Generally, the peaks due to the following fragments are abundant: M+·, [M OCH3]+, [M CH3OH]+·, [M X]+, [M OCH3 CO]+ or [M COOCH3]+, [M X CH3OH]+ or [M OCH3 HX]+, [M OCH3 CO HX]+, [M OCH3 X X]+ and [M OCH3 CO X X]+. Characteristic for the 2- and 4-halo isomers are the primary losses of a methyl radical and methanol, and for the 3-halo isomers the loss of X· from M+·. Disparities between the spectra of the E and Z isomers are shown, the effect of position of halogen substitution being much more pronounced, as reported previously …
Benzyl ions from 1,1-(2,2′-dimethoxyphenyl)-substituted 2-methylpropanes under electron ionization
2006
The electron ionization (EI)-induced fragmentations of a series of 1,1-(2,2'-dimethoxyphenyl)-substituted 2-methylpropanes (1-20) in both 70 eV and mass-analyzed ion kinetic energy (MIKE) spectra have been investigated. The EI-MS spectra of these compounds are characterized by the presence of abundant benzyl ions. These ions result from competitive hydrogen migration from the 2- and 2'-methoxy groups on the carbenium center of the diphenylmethyl cations formed by benzylic cleavage of the molecular ions. The relative abundances of the benzyl ions arising from such competitive processes are discussed and rationalized. The steric effect of the 3- or 3'-substituents is the main discriminating f…
Mononuclear rearrangement of heterocycles in zwitterionic micelles of amine oxide surfactants.
2012
Abstract Rate constants for the mononuclear rearrangement (MRH) of Z -phenylhydrazones of some 5-substituted-3-benzoyl-1,2,4-oxadiazoles in water have been measured in the presence of zwitterionic micelles. The use of micellized N -tetradecyl- N , N -dimethylamineoxide (C 14 DMAO) as the reaction medium allowed to solubilize the otherwise water-insoluble oxadiazoles. Micellar rate effects were analyzed by using a simple pseudo-phase model and compared with those obtained in non-ionic micelles (Triton X-100). Evidence that both the rate of the rearrangement reaction and the binding of the substrates to the micelles are mainly governed by substrate hydrophobicity is obtained. The disagreement…
Contribution à l’étude de la fraction insaponifiable de trois huiles d’olive issues des variétés Guasto, Rougette et Blanquette plantés dans l’est al…
2010
The sterol profile of three Algerian virgin olive oils produced from Guasto, Blanquette and Rougette cultivar’s, varieties grown in the East of the country, was established by gas chromatography using a flame ionization detector and coupled to mass spectrometry. Four sterol compounds were identified and characterized in the three oils which are, sitosterol always predominant (43-66%), delta 5-avenasterol (8-13%), stigmasterol (≤ 1,5%) and campesterol (1-2%); one methyl sterol (4-methylsterol) : citrostadienol (4-7%) and two triterpenic alcohols : 24-methylene cycloartanol (10-33%) and cycloartenol (3-13%). These results vary according to campany and variety. Our study shows that most of the…
Photodimers of cinnamic acid and related compounds. A stereochemical study by electron-impact and field desorption mass spectrometry
1974
The low energy (13 eV) electron-impact and field desorption mass spectra of some photodimers of cinnamic acid and related compounds containing the cyclobutane ring are reported and the fragmentation patterns analysed in order to obtain stereochemical information on the substituent position on the cyclobutane ring. Both symmetrical and asymmetrical splittings of the cyclobutane ring were detected, allowing characterisation of the head-to-head and head-to-tail structures of the title compounds. A ring opening rearrangement of the McLafferty type was also found.