bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stable adduct formation during the gas phase reactions between the trimethylgermanium cation and organic nucleophiles. An ion cyclotron resonance study
Authors: Trenerry V. Craige , Bowie John H. 
Published: May 2005

AbstractThe trimethylgermanium cation (Me3Ge+) reacts with aliphatic organic neutrals (M) which contain N, O or S, to form adducts [M + Me3Ge+] in the gas phase. These adducts are more stable than their analogues formed from the trimethylsilyl cation, and thus Me3Ge+ is a useful analytical reagent for chemical ionization mass spectrometry.
Factors affecting reactivity in ammonia chemical ionization mass spectrometry
Authors: Keough T. , Destefano A. J. 
Published: May 2005

AbstractSeveral factors affecting reactivity in ammonia chemical ionization mass spectrometry (NH3 CI) have been examined. These include the sample proton affinity, the preferred site of protonation and [NH4]+ attachment, and substituent effects. In general, compounds having proton affinities ≲787 kJ mol−1 do not yield analytically useful intensities of the [M·NH4]+ adduct ion. Substituted aromatic compounds in which the ring is the most basic site yield little (if any) [M·NH4]+ ion even if the proton affinity of the compound is greater than 787 kJ mol−1. On the other hand, some aromatic compounds in which the substituent is the most basic site yield relatively abundant adduct ions. The spectra of compounds possessing a good leaving group (X) exhibit only weak [M·NH4]+ ions, but intense [M·NH4 − HX]+ and [M − X]+ ions formed by substitution and elimination reactions. Electronic effects strongly influence these processes. Several examples are presented in which isomers are readily differentiated because of different reactivities under ammonia chemical ionization conditions.
The use of triple quadrupoles for sequential mass spectrometry: 2—A detailed case study
Authors: Dawson P. H. , French J. B. , Buckley J. A. , Douglas D. J. , Simmons D. 
Published: May 2005

AbstractA detailed exploration of the application of triple quadrupoles in sequential mass spectrometry has been carried out using dimethylmorpholinophosphoramidate as a case study of an ion of relatively high mass and complex structure. Both metastable ion decomposition and dissociation by low energy collision were examined. Variation of the basic instrument parameters allowed the investigation of the cross‐section for dissociation as a function of collision energy, the change in fragmentation patterns with collision energy, the kinetic energy distributions of daughter ions and the overall kinetics of dissociation in a succession of ion decomposition sequences giving daughter and granddaughter ions. The daughter ions could also be produced in the source region and examined separately so that a genealogical tree could be established.
Mass spectral fragmentation of ethene and propene dithioketals of cyclobutanone
Authors: Mohammadi Mohammad , Willett James D. 
Published: May 2005

AbstractA detailed analysis of the electron impact induced fragmentation of ethene and propene dithioketals of cyclobutanone is presented. The tetradeuterio analog of the cyclic dithioketals was prepared as an aid in analyzing the fragmentation patterns. Cleavage of the 1,3‐dithiolane ring system is favored at 15 eV, whereas cyclobutane ring cleavage is favored at 70 eV. Thus, the primary fragmentation pathway seems to be dependent upon the ionization energy.
The chemical ionization mass spectra of 2,4‐adamantanediol diacetates and dimethyl ethers
Authors: D'Haenens L. , Van de Sande C. C. , Schelfaut M. 
Published: May 2005

AbstractThe chemical ionization mass spectra of the isomeric 2,4‐adamantanediol diacetates and dimethyl ethers have been determined using methane and isobutane as reagent gases. The significant differences in the spectra of the diacetates allow an unambiguous identification of the isomers. The spectra of the trideuteroacetates reveal the occurrence of protolysis in the ionizing plasma.
Gaseous [C7H8]+˙ ions: [Methylene cyclohexadiene]+˙, a stable species in the gas phase
Authors: Burgers Peter C. , Terlouw Johan K. , Levsen Karsten 
Published: May 2005

AbstractUsing collisional activation and collisional ionization spectra in conjunction with isotopic labelling and energetic data it is demonstrated that the metastable decomposition of ionized n‐butylbenzene and 2‐phenylethanol leads to [C7H8]+˙ ions which have the methylene cyclohexadiene structure. From appearance energies of metastable peaks a value of 960±10 kJ mol−1 was obtained for its heat of formation.
Mass spectrometry of nitroazoles: 3—ortho effects: The loss of OH˙ and H2O from methyl substituted nitrodiazoles
Authors: Luijten W. C. M. M. , van Thuijl J. 
Published: May 2005

AbstractMethyl substituted nitrodiazoles which have the substituents at adjacent positions in the ring are subject to several ortho effects. Deuterium labelling of the methyl group and the mobile N‐bonded hydrogen show that the loss of OH˙ originates from the substituents. In some cases the N‐bonded hydrogen atom participates also in the loss of OH˙ and of H2O.
Concerning the Beckmann rearrangement of aryl heteryl ketoxime ions
Authors: Grützmacher Hans‐fr. , Römer Christian 
Published: May 2005

AbstractThe possible Beckmann rearrangement of aryl heteryl ketoxime ions has been investigated by studies on the 70 eV mass spectra, metastable ion spectra and collision induced dissociation spectra of pairs of isomeric ketoximes and corresponding amides. Aryl cycloalkyl ketoximes were also studied, and the molecular ions of these and the corresponding amides showed no evidence of interconversion. The introduction of the heterocyclic moieties made little change to this situation although some novel rearrangements were observed.
2‐substituted‐2,3‐dihydro‐4H‐pyrans: Competition between ‘retro Diels‐Alder’ fragmentation and substituent loss
Authors: Morizur J‐P. , Mercier J. , Sarraf M. 
Published: May 2005

AbstractThe mass spectra of two series of 2‐substituted‐2,3‐dihydro‐4H‐pyrans (six ethers and six carbonyl derivatives) showed a marked dependence upon the nature of the substituent. α‐Cleavage (substituent loss) was the only primary decomposition observed in the carbonyl series, while ‘retro Diels‐Alder’ reactions competed with α‐cleavage in the ether series. An unambiguous interpretation of this difference in behaviour, based on the consequence of charge localization and thermochemical data, is proposed.
The mechanism of formation of [C4H9O]+ ions from isobutyl ethyl ether
Authors: Audier H. E. , Bouchoux G. , Hoppilliard Y. , Milliet A. 
Published: May 2005

AbstractIt is demonstrated by means of metastable ions characteristics, collisional activation, deuterium labelling and appearance energy measurements that ionized ethyl isobutyl ether and ethyl n‐butyl ether isomerize prior to decomposition. The lower critical energy fragmentation gives [CH3CH2OCHCH3]+ ions. A mechanism of isomerization is proposed in which 1,4 hydrogen migration on the oxygen atom is coupled with rearrangement of the butyl chain.
Derivatization and mass spectrometric investigations of substituted benzeneboronic acids. The use of linked scanning during gas chromatography mass spectrometry
Authors: Longstaff Colin , Rose Malcolm Edward 
Published: May 2005

AbstractSubstituted benzeneboronic acids are important intermediates in the synthesis of support matrices for affinity chromatography but their analysis by mass spectrometry is hindered by thermal reactions in the ion source. A simple derivatization with 1,2‐ or 1,3‐diols removes this difficulty and imparts sufficient volatility for application of gas chromatography/mass spectrometry. The mass spectra of the resulting boronate esters are discussed with reference to high resolution measurements, isotope labelling studies and observation of metastable ions. ortho Substituents are shown to interact strongly during fragmentation. Linked scanning at constant B/E was used to characterize fragmentation pathways and the compatibility of linked scanning and GC/MS is reported.
Mass spectra of chlorinated esters: 2—Methyl mono‐ and dichlorobutanoates
Authors: Korhonen Ilpo O. O. 
Published: May 2005

AbstractThe mass spectral fragmentations of methyl mono‐ and dichlorobutanates have been studied. Deutrium labelling and metastable ion analysis were used to elucidate the fragmentation mechanisms. The molecular ion peaks of the esters are weak and show only in the spectra of the monochloro isomers. A McLafferty rearrangement gives the base peaks in the spectra of methyl 2‐chloro‐, 4‐chloro‐ and 4,4‐dichlorobutanoate; α‐cleavage, [COOCH3]+, in methyl 2,2‐ and 2,4‐dichlorobutanoate; [MCl]+, in methyl 3‐chlorobutanoate; [MClHCl]+, in methyl 3,4‐dichlorobutanoate; [MClCH2CO]+, in methyl 3,3‐dichlorobutanoate and [MClCOOCH3]+˙, in methyl erythro‐ and threo‐2,3‐dichlorobutanoate. The mass spectra of the stereoisomers are nearly identical, the loss of a chlorine atom and the McLafferty rearrangement giving the higher peaks in the spectrum of the threo form.
Cyclic organophosphorus compounds: XVII—the mass spectra of some 5,5‐dimethyl‐perhydro‐1,3,2‐oxazaphosph(v)orines
Authors: Edmundson R. S. 
Published: May 2005

AbstractThe electron impact mass spectra of six 5,5‐dimethyl and eleven 3,5,5‐trimethyl‐perhydro‐1,3,2‐oxazaphosphorine 2‐oxides and 2‐sulphides are reported and compared with those of analogous 5,5‐dimethyl‐1,3,2‐dioxaphosph(v) orinans. Compounds of the 3,5,5‐trimethyl series produce an important ion at m/z 44 which clearly distinguishes them from the 5,5‐dimethyl series. The 2‐sulphides are characterized by loss of thiol radical rather than of sulphur; in the case of 2‐cyclohexylamino‐3,5,5‐trimethyl‐perhydro‐1,3,2‐oxazaphosphorine 2‐sulphide at least, the thiol hydrogen is derived from the oxazaphosphorine ring NCH2 group. Fission of the oxazaphosphorine ring occurs largely, but apparently not exclusively, at the POC linkages.
Gas chromatographic mass spectrometric indication of double bond position in monounsaturated primary acetates and alcohols without derivatization
Authors: Leonhardt B. A. , DeVilbiss E. D. , Klun J. A. 
Published: May 2005

AbstractElectron impact mass spectra of straight chain, monounsaturated C12 to C18 acetates and alcohols have been shown to be useful in the indication of the double bond position on an empirical basis. The ratio of intensities of the m/z 55 and m/z 54 ions increases proportionately as the double bond is moved away from the acetate or alcohol functional group. The intensity of the m/z 61 ion also can be correlated with the double bond position. Results are generally accurate to ±1 carbon atom.
The methylamine radical cation [CH3NH2]+˙ and its stable isomer the methylenammonium radical cation [CH2NH3]+˙
Authors: Bouma Willem J. , Dawes Judith M. , Radom Leo 
Published: May 2005

AbstractThe potential energy surface for the [CH5N]+˙ system has been investigated using ab initio molecular orbital calculations with large, polarization basis sets and incorporating valence‐electron correlation. Two [CH5N]+˙ isomers can be distinguished: the well known methylamine radical cation, [CH3NH2]+˙, and the less familiar methylenammonium radical cation, [CH2NH3]+˙. The latter is calculated to lie 8 kJ mol−1 lower in energy. A substantial barrier (176 kJ mol−1) is predicted for rearrangement of [CH2NH3]+˙ to [CH3NH2]+˙. In addition, a large barrier (202 kJ mol−1) is found for loss of a hydrogen radical from [CH2NH3]+˙ via direct N—H bond cleavage to give the aminomethyl cation [CH2NH2]+. These results are consistent with the existence of the methylenammonium ion [CH2NH3]+˙ as a stable observable species. The barrier to loss of a hydrogen radical from [CH3NH2]+˙ is calculated to be 140 kJ mol−1.
Effect of overcrowding in mass spectra for six violanthrenes
Authors: Ueda Toyotoshi , Ohno Mitsuru , Harada Hisashi , Iwashima Satoshi , Aoki Junji , Kan Teruo 
Published: May 2005

AbstractThe mass spectra of six highly purified violanthrene samples of class A—(benzo[rst]anthro[10,1,2‐cde]pentaphen, benzo[rst]phenanthro[10,1,2‐cde]pentaphene), class B—(benzo[rst]phenanthro[1,10,9‐cde]pentaphene, dibenzo[a,rst]naphtho[8,1,2‐cde]pentaphene) and class T—(tetrabenzo[a,cd,j,lm]perylene, tetrabenzo[de,hi,op,st]pentacene) were measured. The dependence of relative ion instensities for monovalent, divalent and trivalent ions [M]i+, [M – 2n]i+ and [M – 15]i+ (i = 1, 2, 3) showed clearly the effect of overcrowding in condensed aromatic rings, i.e. the number of H2 molecules which are readily eliminated from the molecular ions is zero for class A, one for class B, and two for class T. These numbers are the same as the number of overcrowded hydrogen atom pairs for each class.
Pyrolysis reaction of carpronium chloride and its structurally related compounds. 2—a mass spectrometric study of the lactonization mechanism
Authors: Ohya Kazumi , Kitaoka Hiroaki , Yotsui Yasuhiko , Sano Mitsuji 
Published: May 2005

AbstractThe mechanism of the pyrolysis reaction of carpronium chloride [(CH3)3N+(CH2)3COOCH3CI−] leading to γ‐butyrolactone and tetramethylammonium chloride was investigated by means of thermal analysis, pyrolysis gas chromatography mass spectrometry and field desorption mass spectrometry, using deuterium labelling. The results indicated that carpronium chloride pyrolysed to yield equimolar amounts of γ‐butyrolactone and tetramethylammonium chloride, methyl transfer occurred between N and O during the pyrolysis process. The mechanism is discussed on the basis of the experimental results, and with the aid of the theoretical results calculated by the CNDO/2 method. The mechanism presented is as follows. γ‐Butyrolactone is formed by the intramolecular migration of the π‐orbital of CO to the carbon adjacent to [(CH3)3N]+ via a 5‐membered ring transition state, accompanied by a bimolecular reaction between [(CH3)3N]+ and the CH3 of OCH3, resulting in the formation of tetramethylammonium chloride in an amount equimolar with γ‐butyrolactone.
An electron impact study of HCN elimination from indolizine by use of 13C labelling
Authors: Corval Madeleine , Lautié Marie‐France 
Published: May 2005

AbstractThe study of the loss of HCN from the molecular ions of [1‐13C]‐, [2‐13C]‐ and [3‐13C]‐indolizine shows that, if the C‐3 atom is eliminated predominantly, as may be expected, the C‐2 atom, and (a) carbon atom(s) of the hexagonal ring are also involved. The losses of 13CCH3. and C2H3. from the [MH12CN]+˙ ions of the three compounds point to the interference of distinct mechanisms of HCN elimination, leading to different structures for the [C7H6]+˙ ions.
Collisionally activated dissociation of field desorbed protonated dinucleoside phosphates
Authors: Linscheid M. , Burlingame A. L. 
Published: May 2005

AbstractThe collisionally activated dissociation (CAD) of six protonated dinucleoside monophosphates produced by field desorption has been studied by linked scanning (B/E=constant). Complete spectra with detailed structure information have been obtained despite the small ion currents and other technical problems. It is possible to distinguish isomeric sequences in both ribo‐ and deoxyribo‐nucleotides series.
Mass spectral analysis of schiff bases derived from 1,1,1‐trifluoro‐2,4‐pentanedione and 1,2‐diaminoethane, 1,3‐diaminopropane, 1,4‐diaminobutane and 1,2‐diaminobenzene and their copper(II) and nickel(II) complexes
Authors: Morris M. L. , Koob R. D. 
Published: May 2005

AbstractThe mass spectra of the title compounds have been determined and special attention has been given to metastable transitions and ion composition assignments. The interpretation of the mass spectra of N,N'‐ethylenebis(5,5,5‐trifluoro‐4‐oxopentan‐2‐imine) and its metal complexes is relatively straightforward. Bond breaking α and β (with H transfers) to nitrogen in the ethylenediamine portion of the molecule overwhemingly dominates the spectra. Changing the diamine bridge adds new features to the spectra in both expected and unexpected ways. Ligand fragmentation changes little when complexed to nickel as compared to hydrogen. Chelation of Cu(II) on the other hand leads to new fragmentation channels which increase in importance as electron availability in the diamine bridge increases. These new reactions are attributed to a reduction of the copper centre in the molecule.
Electron impact induced water elimination from hydroxyamides. 1—N‐(2′‐hydroxyethyl)piperidone‐2 and N‐3′‐hydroxypropyl piperidone‐2
Authors: Steiner B. , Schumann D. , Hoffmann H. 
Published: May 2005

AbstractThe main process of the electron impact induced water elimination of the title compounds takes a reaction course comprising several individual steps. A characteristic neighbouring group participation of the carbonyl function is involved, onto which a hydrogen is transferred in a first rate‐determining reaction step. This rearranged hydrogen is finally lost together with the hydroxyl group. The reaction of N‐(2′‐hydroxyethyl)piperidone follows what seems to be a [1,1] elimination whereas the H2O elimination from N‐(3′‐hydroxypropyl)piperidone represents a formal [1,2] elimination.
Internal energy and angular momentum effects on collision induced dissociation fragmentation patterns
Authors: Jarrold M. F. , Illies A. J. , Kirchner N. J. , Bowers M. T. 
Published: May 2005

AbstractData are reported on the effects of internal energy and angular momentum on the collision induced dissociation CID fragmentation pattern. For the ions studied changes in the relative intensities of the fragment ions as internal energy varied were found to be larger than suggested by McLafferty and coworkers. Possible effects of angular momentum on the CID fragmentation pattern are discussed. The charge stripping spectra of the ions studied were found to be strongly dependent on initial energy and/or angular momentum. Hence care must be taken if charge stripping spectra are used to distinguish ion structures.
Intramolecular single and double hydrogen migrations in the mass spectra of substituted tetrahydro‐1,3,2‐oxazaphosphorin‐2‐oxides
Authors: Kulkarni P. S. , Gogte V. N. , Modak A. S. , Sahasrabudhe S. D. , Tilak B. D. 
Published: May 2005

AbstractThe mass spectral fragmentation of substituted tetrahydro‐1,3,2‐oxazaphosphorin‐2‐oxides occurs by the cleavage of ring bonds. The ions due to simple cleavage, single and double hydrogen migration, seem to be triggered by CO bond cleavage of the oxazaphosphorin ring. The variations in the relative abundance of ions arising due to similar fragmentation modes have been found to depend on the nature of the substituent and the stability of the particular fragment. The single hydrogen transfer process is supported by metastable ion and shift techniques.
Isomeric [C3H4]+· ions: Their identification and generation in dissociative ionizations
Authors: Mommers A. A. , Burgers P. C. , Holmes J. L. , Terlouw J. K. 
Published: May 2005

AbstractThe collisional activation (CA) and charge stripping (CS) mass spectra of the three [C3H4]+· isomers, allene, propyne and cyclopropene, are reported. The extent of isomerization among these ions prior to collisional excitation depends on their internal energy content, but is small. Each [C3H4]+· ion structure also can uniquely be generated via appropriate dissociative ionizations. Analysis of mixtures of [C3H4]+· (daughter) ion structures is, in general, not possible from CA and CS mass spectra alone but may be aided by appearance energy measurements.
Mass spectra of halogenated esters 5—Chloromethyl esters of aliphatic C2C12n‐carboxylic acids and their monochlorinated derivatives
Authors: Korhonen Ilpo O. O. 
Published: May 2005

AbstractA study has been made of the mass spectral fragmentation upon electron impact of aliphatic C2C12 chloromethyl esters and all their 66 monochlorinated derivatives. The fragmentation pathways of the parent chloromethyl esters were elucidated with the aid of the 1st FFR metastable ions. A McLafferty rearrangement gives the base peak in the C6C11 parent esters and in almost all the 4‐chloro and ω‐chloro isomers. The subsequent loss of HCl gives a very characteristic peak of the chloromethyl esters and their (3‐ω)‐chloro derivatives at m/z 72, [C3H4O2]+. The 2‐chloro isomers have the corresponding chlorine‐containing fragment ion at m/z 106/108. The mass spectra of 2‐, 3‐, 4‐, 5‐ and ω‐chloro isomers give the characteristic fragment ions, the mass spectra of the other isomers being very similar.
Mass spectral studies of alkylbenzenesulphonic acids through their S‐benzylisothiouronium salts
Authors: Borthakur Arun , Rao V. S. Bhaskar 
Published: May 2005

AbstractThe mass spectra of alkylbenzenesulphonic acids in the form of their S‐benzylisothiouronium salts have been studied. These S‐benzylisothiouronium salts dissociated into two parent reactant ions: (i) alkylbenzenesulphonic acid and (ii) S‐benzylisothiourea. The characteristic fragmentation patterns of alkylbenzenesulphonic acids (0‐5 substituted alkyls) were studied and compared with those of the parent hydrocarbons. The intensity of the molecular ion peak decreased with the increase in the molecular weight of the sulphonic acids. Desulphonation as well as loss of the alkyl group was observed in all the spectra. Migration of the alkyl group from S to O, followed by degradation, was also observed in all the spectra studied.
Fast atom bombardment mass spectrometry of non‐volatile organometallic compounds. Rhodium, iridium and platinum complexes containing a cumulene ligand
Authors: Sharp Thomas R. , White Mitchell R. , Davis Jon F. , Stang Peter J. 
Published: May 2005

AbstractFast atom bombardment (FAB) mass spectrometry has been used to examine a series of rhodium, iridium and platinum organimetallic complexes, in which a cumulene ligand is attached to the metal in either σ‐or π‐bonding fashion. The most intense ion formed in the rhodium and platinum series is the metal‐bis(triphenylphosphine) ion, while the [Ir(P(C6H5)3)2CO]+ ion is most intense for the iridium series. The platinum complexes show the most intense molecular ion peaks (up to 35% relative intensity), while the rhodium complexes show the least intense molecular ion peaks. The primary fragmentations of all these complexes occur at the metal‐ligand bonds. The cumulenic ligand is lost as an impact unit in all cases. The FAB mass spectra of Rh(P(C6H5)3)3Cl (Wilkinson's catalyst), Ir(P(C6H5)3)2COCl (Vaska's compound), Rh(P(C6H5)3)2COCl and Pt(P(C6H5)3)2(C2H4)–synthetic precursors or related compounds to the organometallic complexes examined here–are included for comparison.
Mass spectrometry of organic compounds of group V elements 7—N‐alkoxyamines
Authors: Kostyanovsky R. G. , Pleshkova A. P. , Voznesensky V. N. , Rudchenko V. F. , Sh. Trokhova S. 
Published: May 2005

AbstractThe suggestion of participation of the participation Ione electron pair of the nitrogen atom in amine‐type stabilization has been confirmed by a decrease in amine‐type fragmentation and a drastic change in the decomposition routes under electron impact of N‐alkoxyamines.