bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass spectrometry of steroid systems—XXI Appearance and ionization potentials for the stereo‐isomers of the D‐homoestrane series
Authors: Zaretskii V. I. , Sadovskaya V. L. , Wulfson N. S. , Sizoy V. F. , Merimson V. G. 
Published: May 2005

AbstractThe ionization potentials of methyl ethers of D‐homoequilenine, its 14ß‐isomer, D‐homoestrone and its 8°‐isomer, as well as appearance potentials of certain fragment ions have been determined by means of electron‐impact. The dissociation energies of the bonds which are split in the course of formation of these ions have been calculated.
Valency changes of sulphur in the mass spectra of sulphones
Authors: Soothill Rayner J. , Williams L. R. 
Published: May 2005

AbstractThe aryl substituent has been shown to affect the fragmentation and abundance of skeletal rearrangement ions in the spectra of aryl sulphonyl chlorides and sulphonic acids. The spectra of 2‐hydroxy and 2‐chloroethyl aryl sulphones contain [aryl SO]+ ions, suggesting that alkyl migration has competed successfully with aryl migration to the electron deficient oxygen atom.
Mass spectrometry of onium compounds—IX: On the evaporation of anilinium oxides. Ionization potential measurements
Authors: Hvistendahl Georg , Undheim Kjell 
Published: May 2005

Abstracto‐N,N,N‐Trimethylanilinium oxide is evaporated structurally unchanged, admixed with the corresponding transalkylated ether. The ionization potential for the anilinium oxide was determined as 6·8 eV which was 0·8 eV lower than for the corresponding ether. An explanation for the unusually low IP value is advanced. In IP measurements in binary mixtures the semi‐log plot method showed parallel curves for different compositions in the gas phase, but no linear relationship between the recorded IP and composition was found. Appearance potential measurements show that the energy of the zwitterion in the gas phase is at least 10 kcal/mol higher than in the corresponding ether.
Charakteristika in den Massenspektren von Spermidin‐Derivaten
Authors: Bosshardt H. , Veith H. J. , Hesse M. 
Published: May 2005

AbstractDas Massenspektrum von N,N′,N″‐Triacetylspermidin (I) zeichnet sich durch charakteristische Signale bei m/e 143, 157 und 169 aus. De Reaktionen, die zu den entsprecenden Ionen führen, lassen sich nicht durch Anweding einfacher Fragmentierungsreaktionen erklären. Auf der Bzasis der Massenspektren deuterierter Derivate von I werden Fragmentierungsmechanismen vorgeschlagen. Interessanterweise ist hauptsächlich der 1, 3‐Diaminopropan‐Teil und weiniger der 1, 4‐Diamino‐butan‐Teil (Putrescin) des Spermidin‐Moleküls an den Abbaureaktionen zu den erwänten Ionen beteilligt. Die beiden teriären Sticktoffatome des Diaminopropanteiles sind im wesentlichen die Promotoren der Fragmentierung, wie aus den Schematatas 2 bis 7 hervorgeht. Dieser Verlauf des massenspektrometrischen Zerfalls des trifunktionellen Spermidin‐Derivates verläuft ser ähnlich dem Zerfall bifunktioneller Alkane.
The mass spectra of carboxylic acids·IV: Carboxyl‐carboxyl interaction in some cycloalkane 1,2 dicarboxylic acids and its relationship with molecular geometry
Authors: Benoit F. , Holmes J. L. 
Published: May 2005

AbstractThe interaction of the carboxyl groups in the fragmentation of the molecular ions of trans cyclohexane‐1,2‐dicarboxylic acid and cis cyclobutane‐1,2‐dicarboxylic acid serves to distinguish these acids from their cis and trans isomers respectively. This ‘ortho effect’ can be related to the geometrical arrangement of the carboxyl groups in the ground‐state molecules.
Mass spectra of geometrical isomers: The isomeric 3‐ and 7‐cyclohexyl‐2‐norbornanols
Authors: Chen Paul H. , Kuhn William F. , Kleinfelter Donald C. , Miller James M. 
Published: May 2005

AbstractThe mass spectra of isomeric 3‐ and 7‐cyclohexyl‐2‐norbornanols have been studied. The 3‐substituted norbornanols give very similar mass spectra, whereas large differences were observed between the mass spectra of 7‐syn and 7‐anti isomers. While the mass spectra of these bicyclic alcohols show extensive rearrangements to give rise to many odd‐electron ions, the Wagner‐Meerwein rearrangement of the molecular ion prior to fragmentation or during the process of dehydration is not important. The origins and the mechanisms for the formation of some major ions are discussed in terms of low voltage spectra, defocused metastables and their relative abundances, and ionization or appearance potentials of the ions of interest.
Mass spectrometry of onium compounds—XI: Ionization potentials of hydroxy and mercapto pyridines
Authors: Grønneberg Truls , Undheim Kjell 
Published: May 2005

AbstractIonization potential measurements of the volatile species from the three isomers of the tautomeric hydroxyl and mercapto pyridines show that these are in the hydroxy and mercapto forms rather than appearing as lactams and betaines. The corresponding N‐methyl lactams and S‐ and O‐methyl ethers were also studied for comparative purposes.
Competing metastable transitions of the [C7H6F]+ ion
Authors: Jennings K. R. , Whiting Alan 
Published: May 2005

AbstractMetastable transitions arising from the loss of C2H2 and HF from the [C7H6F]+ ion have been investigated. Under standard operating conditions, the intensity ratio of the metastable peaks was approximately independent of the precursor of the [C7H6F]+ ion, indicating fragmentation from a common structure such as the symmetrical fluorotropylium ion. The variation of the intensity ratio with several instrumental parameters suggests that I(C2H2 loss)/I(HF loss) rises as the internal energy of the [C7H6F]+ ion falls. Possible interference from discrimination effects at the β‐slit when comparing intensity ratios for first and second field free region are discussed.
Mass spectrometry of organic compounds in the group V elements—I: Straight chain aliphatic derivatives
Authors: Kostyanovsky R. G. , Plekhanov V. G. 
Published: May 2005

AbstractComparative investigations of the mass spectra of eEH2, Me2EH, Et2EH(E = N, P); Me3E, Et3E(E = N, P, As, Sb, Bi). (n‐Pr)3E(E = Sb, Bi); (n‐Bu)3E(E = P, As); (n‐C5H11)3As and (n‐C6H13)3As as well as Et2AsBr have been carried out. Deuteroanalogues, metastable transitions and low voltage spectra were used for elucidation of the fragmentation paths. The mass spectra of MeN(CH2)2 and CD3N(CH2)2 were studied to analyse the structure of the fragments. The main degradation path of amines, i.e. α‐cleavage, was shown to be untypical for P, As, Sb and Bi derivatives.
Mass spectrometry in structural and stereochemical problems—CCXXI: The loss of methyl from the [M  C2H4]+· ion of butyrophenone
Authors: Tomer Kenneth B. , Djerassi Carl 
Published: May 2005

AbstractThe expulsion of CH3· from the [M  C2H4]+· ion of butyrophenone occurs with loss of a ring hydrogen and the methylene group as evidenced by deuterium labeling and metastable transitions.
Azabicyclo Compounds—XI. A study of the fragmentation processes of quinuc‐lidine and some of its derivatives
Authors: Paleček J. , Mitera J. 
Published: May 2005

AbstractThe mass spectra of quinuclidine, all the ring position deuterated analogues and some methyl homologues have been measured. Plausible mechanistic interpretations of principal fragment ions are discussed, in the case of quinuclidine, with the help of deuteration in all the ring positions.
Analysis of organic salts by laser ionization mass spectrometry. Sulfonates, sulfates and thiosulfates
Authors: Mumma R. O. , Vastola F. J. 
Published: May 2005

AbstractSodium and potassium salts of organic sulfonates (1‐decyl, 1‐dodecyl and 1‐hexadecyl), sulfates (1‐hexyl, 1‐decyl and 1‐octadecyl) and thiosulfates (1‐octyl, 1‐dodecyl, 1‐tetradecyl, 1‐hexadecyl, benzyl and β‐phenylethyl) were ionized by laser irradiation and the positive ions were analyzed by time‐of‐flight mass spectrometry. The organic ions observed were always intense and due to the molecular species plus a cation or a dimer plus a cation. The spectra of the thioslufates and sulfates show an abundance of inorganic ions in contrast to the sulfonates. The thiosulfate spectra are characterized by intense [Na3SO3]+ or [K3SO3]+ ions and the sulfates by intense [Na3SO4]+ or [K3SO4]+ ions.
Ringschlussreaktionen in der Elektronenstoss‐Induzierten Fragmentierung des Nicotins
Authors: Liehr J. G. , Schulze P. , Richter W. J. 
Published: May 2005

AbstractDie Frage der Herkunft und Struktur des intensiven [M – 29] Fragments im Massenspektrum von Nicotin wird erneut diskutiert. Deuteriummarkierung, Hochauflösungsmessungen und Analyse von metastabilen Uebergängen mit neuartigen Methoden legen eine zweistufige Genese nahe: Eliminierung einer neutralen Aethylenpartikel aus dem Pyrrolidin‐Moleküteil (C‐3 und C‐4), gefolgt von verlust eines Wasserstoffatoms aus der 2′‐oder in gleichem Ausmass aus der 4′‐Position des Pyridinringes. Dieser zweite Schritt kann durch die Annahme einer Zyklisierung der [M – 28] Zwischenstufe erklärt werden, deren radikalisches Zentrrum die ortho‐oder mit gleicher Wahrscheinlichkeit die para‐position des Pyridinringes (2′‐ bzw. 4′‐) angreift und zur Substitution des jeweiligen H‐Atoms führt.
Mass spectra of 1,2,4‐triazoles—II: Alkyl 1,2,4‐triazoles
Authors: Blackman A. J. , Bowie J. H. 
Published: May 2005

AbstractThe mass spectra of monomethyl 1,2,4‐triazoles contain fragment ions produced by specific cleavage of the heterocyclic ring. A major fragmentation from many molecular ions involves the elimination of HCN, but loss of N2 is either very small or completely absent. No N or H scrambling occurs within the triazole ring system, as evidenced by labelling studies. The loss of a hydrogen atom from the molecular ions of 3‐alkyl‐1,2,4‐triazoles (alkyl ⩾ C2H5) originates from hydrogens attached to the β carbon and nitrogen atoms.
A conversational mass spectral search and retrieval system—II: Combined search options
Authors: Heller Stephen R. , Fales Henry M. , Milne G. W. A. 
Published: May 2005

AbstractAn interactive, conversational mass spectral search system based on 8782 uncertified electron‐impact mass spectra and accessible over ordinary telephone lines, is described. Compounds whose mass spectra are in the file can be immediately identified and very useful structural inferences can be obtained for compounds that are not represented in the file. The file may be searched in a number of ways, including by peaks and intensities, molecular weight, complete and partial molecular formula, molecular weight plus peaks/intensities, molecular formula plus peaks/intensities and molecular weight plus molecular formula. Lastly, the complete spectrum of any compound in the file can be printed out.
The ion kinetic energy spectra of some chlorinated insecticides
Authors: Safe S. , Hutzinger O. , Jamieson W. D. , Cook M. 
Published: May 2005

AbstractThe ion kinetic energy (IKE) spectra of the p,p′ and o,p′ DDT, DDD and DDE isomers have been examined. The results indicated that the decomposing [M‐CCl3] ions (b) (m/e 235) for the p,p′ and o,p′ DDT isomers were not energetically similar, suggesting retention of the positional identity of the aromatic chlorine substituents. Similar results were obtained for the [M – CHCl2] ions (b) for the p,p′ and o,p′ DDD isomers. The IKE spectra of p,p′ and o,p′ DDE were indistinguishable, indicating loss of substituent identity of the aromatic chlorine group. The mechanistic and analytical consequences of these data are discussed. The IKE spectra of the four hexachlorocyclohexane isomers (V to VIII) are different and these spectra are obviously useful in the analysis and characterization of these structurally similar compounds. The differences in their reactivity must in some part be due to their different stereochemical orientations of the chlorine substituents.
Mass spectrometry of onium compounds—XX: Ionisation potential in structural assignment of some gaseous molecules
Authors: Fjeldstad Per Einar , Undheim Kjell 
Published: May 2005

AbstractThe ionisation potentials for a series of thiazolo[3,2‐a]pyridinium‐3‐oxides are reduced by about 1.7 to 1.8eV on introduction of an 8‐OH group. The gaseous species from the former compounds are ascribed a mesoion, structure while the hydroxy‐derivatives are rearranged to non charged molecules.
Mass spectrometry of xanthones‐I: The electron‐impact‐induced fragmentation of xanthone, monohydroxy‐ and monomethoxyxanthones
Authors: Arends Peter , Helboe Per , Møller Jøgen 
Published: May 2005

AbstractWith the aid of isotopic labelling (D and 18O) and the metastable defocusing technique the mass spectra of xanthone, the monohydroxyxanthones and the monomethoxyxanthones have been recorded and interpreted. The relative position of the hydroxy group exerts no direct effect on the fragmentation, whereas the decomposition of the methoxy compounds is clearly influenced by the position of the substituent. The 1‐methoxy‐group exhibits an ‘Ortho‐effect’. The presence and significance of doubly‐charged ions in the spectra are discussed.
Mass spectra of organoarsenic compounds—II: Electron‐impact‐induced fragmentation of 2‐substituted‐1,2,2‐dioxarsenanes
Authors: Frøyen Paul , Møller Jøgen 
Published: May 2005

AbstractThe electron‐impact‐induced fragmentation of 2‐substituted 1,3,2‐dioxarsenanes has been studied. The main fragmentation modes have been determined with the use of high resolution mass measurements and by application of the metastable defocusing technique. The predominant fragmentation for the 2‐alkyl‐1,3,2‐dioxarsenanes proceeds via the loss of the 2‐substituent from the molecular ion. In the case of 2‐phenyl‐1,3,2‐dioxarsenanes elimination of the phenyl group competes with the formation of a C6H5 As ion as well as loss of aldehyde from the molecular ions.
Collisional activation spectra. Behavior of [C3H7O]+ and other [CnH2n+1O]+ ions
Authors: McLafferty F. W. , Sakai Ikuo 
Published: May 2005

AbstractCollisional activation spectra have identified (i) as Stable ion structures. Evidence is presented for a variety of pathway for their formation, including anchimeric assistance and hydrogen migration in less stable isomers. The fragmentation behavior of a number of [CnH2n+1O]+ isomers of n = 2 to 5 shows that extensive rearrangements are common, but that some reactions appear to be useful for ion structure elucidation. One reaction identified is unusual in that it represents the decomposition of an even‐electron ion to yied an odd‐electron ion product in significant abundance.
The mass spectra of ω‐amino acid derivatives. The role of ω‐activation in production of ions upon electron‐impact
Authors: Osman S. , Hoagland P. , Dooley C. J. 
Published: May 2005

AbstractThe mass spectra of a series of N‐phthaloyl and N‐trifluoroacetyl derivatives of ω‐amino acids ranging from 3‐aminopropionic acid to 6‐aminohexanoic acid were determined. Ions of significant intensity resulting from the loss of neutral fragments from precursor ions were observed. Deuterium labeling studies indicate the initial fragmentation loss of a neutral molecule; i.e. the loss of water from the molecular ion involves ω‐hydrogen loss from the alkyl chain. A fragmentation scheme consistent with metastable, high resolution and deuterium labeling data is presented.
Applications of molecular orbital theory to the interpretation of mass spectra. Prediction of primary fragmentation sites in organic molecules
Authors: Loew Gilda , Chadwick Michael , Smith Dennis 
Published: May 2005

AbstractSemi‐empirical molecular orbital calculations have been carried out on the steroidal hormone estrone, both as a neutral molecule and the corresponding positively charge molecular ion. These calculations provide estimates of bond densities and net atomic charges, factors deemed important in past correlations of observed mass spectra with molecular structure. Calculated net charges appear to be unrelated to fragmentation processes. Calculated bond densities of the ground state molecular ion of estrone allow prediction of gross features of fragmentation. Bond densities of excited electronic states of the molecular ion may provide a basis for finer distinction among sites of initial bond cleavage, which is information crucial to rationalization of subsequent fragmentation of the molecular ion.
Fragmentation de Triazoles sous l'Impact Electronique–III Benzotriazole et Derives Alkyles
Authors: Maquestiau A. , Van Haverbeke Y. , Flammang R. , Pardo M. C. , Elguero J. 
Published: May 2005

AbstractLes spectres de masse du benzotriazole et de quelques dérivés alkylés sont discutéS. Seul le tautomère 1H‐benzotriazole est mis en évidence en phase gazeuse. L'‘ion moléculaire’ du 2H‐benzotriazole est formé par érlimination d'éthylèene au départ du 2‐éthylbenzotriazole; une isomérisation en tautomère 1H précède la fragmentation (perte d'azote). On observe une réaction d'extension cyclique au niveau des ions [M‐CH3]+ des 1‐éthyl‐et 2‐éthylbenzotriazoles.
The electron‐impact‐induced fragmentation of acridine
Authors: Acheson R. M. , Aplin R. T. , Bolton R. G. 
Published: May 2005

AbstractStudies of both high and low resolution spectra, and of metastable decompositions occurring in both the first and second field‐free regions of the mass spectrometer have led to a postulated scheme for the fragmentation of acridine under electron‐impact. There is no specific loss of label from either [9‐2H1]acridine or [4,5‐2H2]acridine in any fragmentation, nor is there any total scrambling of label in either molecular ion prior to loss of HCN. There is certainly some degree of scrambling preceding HCN loss from [M]+˙ at 70 eV, but this does not involve the 9‐H to any detectable extent. There is no strong evidence for the acridine molecular ion having the same structure as that of four other C13H9N isomers.
Mass spectrometric studies of peptides—VI:. Applications of metastable ion and collisional activation spectra
Authors: Levsen K. , Wipf H.‐K. , McLafferty F. W. 
Published: May 2005

AbstractAn unambiguous differentiation between leucine and isoleucine residues in peptides is possible with unimolecular metastable ion (MI) and collisional activation (CA) spectra. The immonium ion \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm [Y}\!\mathop {\rm N}\limits^{\rm + } {\rm H = CHC}_{\rm 4} {\rm H}_{\rm 9} {\rm ]} $\end{document}, which is present in the normal mass spectra of all leucine or isoleucine containing peptides, yields MI spectra with which this differentiation can be made with high sensitivity. The MI and CA spectra of other peptide fragments are also applicable in particular cases. MI and CA spectra can also be used to obtain information on the amino acide sequences of individual ions. In general more extensive sequece information is available from CA than from MI spectra. This information appears to be particularly promising for the sequencing of oligopeptide mixtures or of ions produced by field or chemical ionization.
The mass spectra of isomeric hydrocarbons—II: The C5H8S isomers, spiropentane, cyclopentene, 1,3‐pentadiene and isoprene; The mechanisms and energetics of their fragmentations
Authors: Holmes J. L. 
Published: May 2005

AbstractThe mass spectra of spiropentane, cyclopentene, 1,3‐pentadiene (piperylene), isoprene and some deuterium labelled analogues have been studied. The heats of formation of the molecular ions and the major daughter ions [C5H7]+ and [C4H5]+ have been estimated. Fragmentation of these molecules mostly proceeds via common intermediates in which hydrogen atoms have lost their positional identity. Only spiropentane displays any specific fragmentation behaviour related to its ground state geometry.
Mass spectra of the bitter principles fromPicrasma ailanthoides Planchon
Authors: Murae Tatsushi , Sugie Akihiko , Moriyama Yoshihiko , Tsuyuki Takahiko , Takahashi Takeyoshi 
Published: May 2005

AbstractThe mass spectra of several bitter principles isolated from Picrasma ailanthoides Planchon (= P. quassioides Bennett) have been measured and characteristic fragmentation patterns useful for structure elucidation shown. The mass spectra of some related compounds are also described.
Mass spectrometry of uronic acid derivatives: VI—Fragmentation of methyl(methyl 2,3,4‐tri‐O‐methyl‐α‐D‐glucopyranosid)uronate and its analytical application
Authors: Kováčik Vladimír , Kováč Pavol 
Published: May 2005

AbstractThe fragmentation mechanisms of the title compound upon impact with 70 and 12 eV electrons has been studied using specific trideuteriomethyl derivatives. By application of the proposed fragmentation mechanisms, the number as well as the location of methyl groups in all theoretically possible methyl derivatives of methyl D‐glucopyranos duronic acid unequivocally can be determined after exhaustive trideuteriomethylation. For this purpose low energy (12 eV) spectra are recommended, as these contain only the structurally significant ions.
Electron‐impact studies. LXXXII—Negative ion mass spectrometry of functional groups. Collision induced spectra of the carboxyl group
Authors: Bowie J. H. 
Published: May 2005

AbstractFragmentations of the carboxyl group are not generally observed from molecular anions produced by the capture of slow electrons. Enhancement of the internal energy of the molecular anions by collision excitation allows the detection of the fragmentations of the substituent in the field free regions of the mass spectrometer. Fragmentations include the losses of CO2 or ·CO2H from molecular anions, and the elimination of CO2 from fragment ions.
Zum Mechanismus massenspektrometrischer Fragmentierungsreaktionen: XI—Einfluß von Substituenten auf die Bildung cyclischer Fragment‐Ionen in den Massenspektren von N,N‐Dimethyl‐N′‐2‐chlorphenylformatmidinen und 2‐Chlorformaniliden
Authors: Kuschel Heinz , Grützmacher Hans‐F. 
Published: May 2005

AbstractDie Molekül‐Ionen von N,N‐Dimethyl‐N′‐2‐chlorphenylformamidin (III) und von 2‐Chlorformanilid (IV) verlieren leicht ein Cl‐Atom und bilden Benzimidazolium‐ bzw. Benz‐oxazolium‐Ionen. Fur die Ionisationspotentiale am Phenylkern substituierter III und IV wird, wie für substituierte N,N‐Dimethyl‐N′‐phenylformamidine (I), eine lineare Beziehung zu den Hammettschen σ‐Konstanten gefunden. Für die Auftrittspotentiale der cyclischen Fragment‐Ionen von III und IV läßt sich dagegen keine einfache Beziehung zu den polaren Eigenschaften der Substituenten finden, jedoch macht sich der Einfluß der Substituenten auf die Auftrittspotentiale bei I, III und IV in gleicher Weise bemerkbar. Ebenso werden die Intensitaten der cyclischen Fragment‐lonen von I, III und IV durch Substituenten gleichsinnig beeinflußt und durch elektronenabgebende Substituenten in p‐Stellung stark herabgesetzt. Die Bildung von cyclischen Fragment‐Ionen aus den Molekül‐Ionen von I, III und IV erfolgt daher nach dem gleichen Mechanismus.
Degenerate skeletal rearrangement and energy partitioning in the fragmentation of the norbornyl cation
Authors: Holmes J. L. , McGillivray D. , Isaacs N. S. 
Published: May 2005

AbstractThe electron‐impact‐induced fragmentation of a 13C labelled exo‐2‐norbornyl chloride has been studied. When the norbornyl cation, [C7H11]+, [M – Cl], dissociates by elimination of C2H4, carbon atoms are randomly lost showing that extensive skeletal rearrangement (in addition to the complete hydrogen atom scrambling reported earlier) has taken place in the norbornyl cation prior to dissociation.The metastable ion peak associated with the above fragmentation consists of superimposed gaussian and flat‐top components; it is proposed that these correspond to the formation of isomeric [C5H7]+ daughter ions whose heats of formation differ by ∼0.4 eV.