bluuebunny/crossref_metadata_2025 huggingface dataset:
The decomposition of a triply‐charged metastable positive ion of biphenyl
Authors: Beynon J. H. , Caprioli R. M. , Baitinger W. E. , Amy J. W.
Published: May 2005

The transition, [C12H10]+3→[C11H7]+2 + [CH3]+, has been detected both in the ion kinetic energy spectrum and in the mass spectrum of biphenyl. The width of a resulting ‘metastable peak’ has been measured by setting the magnetic field to accept [C11H7]+2 ions and scanning the high voltage at fixed electric sector voltage. The kinetic energy released in the decomposition, calculated from the peak width, amounted to 4.5 eV. With the assumption that this energy release is due entirely to charge separation, the charge distribution in [C12H10]+3 is discussed. The derivation of the equations used to calculate the energy released is given in the Appendix.
The McLafferty rearrangement in aliphatic aldehydes and ketones—a previously unconsidered mechanistic pathway
Authors: Gerrard A. F. , Hale R. L. , Liedtke R. , Faul William H. , Brown Charles Allan
Published: May 2005

The possibility of a mass spectrometric counterpart to the cyclobutanol formation which is encountered in the photolysis of carbonyl compounds has been investigated by preparing 5,5,5‐[2H3]‐2‐methylpentanal (II) and 6,6,6‐[2H3]‐3‐methylhexan‐2‐one (III) and examining their mass spectra at high and low voltage.
The mass spectra of some naphthoquinones. Lapachol, isolapachol and related compounds
Authors: Elwood Thomas A. , Dudley Kenneth H. , Tesarek Joan M. , Rogerson Peter F. , Bursey Maurice M.
Published: May 2005

Several alkylhydroxynaphthoquinones and chemically related cyclic compounds were subjected to mass spectrometric investigation. Fragmentation pathways were elucidated by use of metastable ions, relative intensities of normal ions and accurate mass measurement. In these series, differences in the spectra of 1,2‐ and 1,4‐naphthoquinones are slight. Evidence for ring expansion in ions from furans is suggested.
Fragmentation of arylated medium‐ring compounds. The question of rearrangement of molecular‐ion precursors to [C4Ar4]+˙
Authors: Hoffman Michael K. , Elwood Thomas A. , Rogerson Peter F. , Tesarek Joan M. , Bursey Maurice M. , Rosenthal David
Published: May 2005

Rearrangement of the molecular ions of tetracyclone, tetraphenylquinone, tetraphenylthiophene dioxide and pentaphenylcyclopentadienol prior to decomposition, rather than formation of a symmetrical [C4Ar4]+˙ ion, is considered as an alternative method for the production of [C2Ar2]+˙. The p‐fluoro substituent is used to elicit information about the positional origins of the [C2Ar2]+˙ fragments. Operation of a double focusing mass spectrometer in the defocused mode reveals that the integrity of the molecular ion in different systems is affected to varying degrees, ranging from total lack of rearrangement to virtually complete scrambling.
The mass spectra of thiochromanone and related compounds
Authors: Harrison A. G. , Thomas M. T. , Still I. W. J.
Published: May 2005

The mass spectra of thiochromanone (I), isothiochromanone (II)‐2‐, 3‐ and 8‐methylthiochromanone and the sulfoxides and sulfones derived from these cyclic sulfides have been determined and the major fragmentation routes established. For the iso series loss of SO or SO2 competes effectively with the retro‐Diels‐Alder reaction; however, for the thiochromanone derivatives the retro‐Diels‐Alder reaction is the major fragmentation route. There is no evidence for rearrangement of the sulfoxides or sulfones to sulfenates or sulfinates, respectively, prior to fragmentation.
Mass spectrometry of hop compounds—II: Mass spectra of related oxygen heterocyclic compounds
Authors: Shaw S. J. , Shannon P. V. R.
Published: May 2005

Mass spectra have been determined of a number of phloroglucinol derivatives and closely‐related compounds encountered in chemical studies of hop components. Initial fission involving acyl, alkyl or alkenyl side‐chains gives predominantly even‐electron ions which then fragment their oxygen heterocyclic rings by elimination of neutral molecules, whilst gem‐dialkenyl centres show preference for loss of an alkenyl group. The fragment ions induced by electron‐impact may be correlated to a useful extent with molecular structure.
Zum Mechanismus massenspektrometrischer Fragmentierungsreaktionen–II: Methoxygruppenwanderungen und Ringfragmentierungen in den Massenspektren der Methylather cyclischer Polyalkohole
Authors: Winkler Johann , Grützmacher Hans‐Friedrich
Published: May 2005

Zusammenfassung‐Die Massenspektren der Methyläther von Cyclopentan‐, cyclohexan, und Cycloheptandiolen besitzen einen deutlichen Peak m/e 75 von Ionen dr Struktur ⊕CH OCH3)2, die durch 1,3‐, 1,4‐ oder 1,5‐Wanderung einer Methoxygruppen entstehen. Die Bildung dieser Ionen ist nicht abhängig von der Stereochemie des Ausgangsmoleküs, vermutlich erfolgt die Methoxygruppenwanderung in einem durch α‐spaltung entstandenen offenkettigen Radikal‐Ion: magnified image

Bei Cycloalkanen mit drei und mehr Methoxygruppen geben die Umlagerungsionen m/e 75 durchweg einen der gröten Peaks der Massenspektren.

Die von einem carbinol‐C‐Atom ausgehenden Bindungen sind geschwächt. Die Anwesenheit mehrerer Carbibnol‐C‐Atome in den Molekül‐Ionen cyclischer Polymethoxyverbindungen begünstigt daher Fragmentierungen. die von den Zerfallsreaktionen einfachr Cyclanolderivate abweichen und charakteristisch für die Stellung der Methoxygruppen sind.
The mass spectra of 5,10‐dihydro‐5‐10‐o‐benzenophenarsazine (azarsatriptycene) and its oxide
Authors: Earley R. A. , Gallagher M. J.
Published: May 2005

The fragmentation of azarsatriptycene and its oxide proceed with initial rearrangement of the molecular ion to give polycyclic systems: it is suggested that similar rearrangements may account for the behaviour of triptycene itself in the mass spectrometer.
Mass spectra of 5,10‐dihydrophenarsazines, 5,10‐dihydrophenarsazine and phenophosphazine oxides, and related heterocycles
Authors: Earley R. A. , Gallagher M. J.
Published: May 2005

The electron‐impact‐induced fragmentation of eight 5,10‐dihydrophenarsazines and three 5,10‐dihydrophenarsazine oxides proceeds by loss of the exocyclic arsenic substituents to give the stable ion (II) as the base peak followed by loss of arsenic to give a carbazole species (III). The fragmentation pattern is independent of substituents at either hetero‐atom in the cases examined. Dihydrophenophosphazine oxides behave similarly but give as the base peak an ion in which the phosphoryl grouping is retained.

10,11‐Dihydro‐5‐phenyl‐5H‐dibenzo[b, f][1,4]azarsepine and 2,3‐dihydro‐1,2‐diphenyl‐1H‐benz [c]azarsole fragment by different pathways. It is suggested that the ability of arsenic and phosphorus to sustain a positive charge by dπ‐pπ bonding is the dominating factor in these fragmentations.
Mass spectral studies on tanshinones
Authors: Hayashi T. , Inouye Y. , Ohashi M. , Kakisawa H. , Tatematsu A. , Kinoshita T.
Published: May 2005

The mass spectra of three groups of tanshinones have been examined and a number of characteristic features noted which might be helpful in the micro‐identification of the natural products. The fragmentation patterns are similar to each other except for the relative intensity within the same group of tanshinones and are accounted for in terms of the general fragmentations of furans and quinones. Characteristic ions at m/e 178, 165 and 152 found in all kinds of tanshinones may be considered to be of highly aromatized hydrocarbon fragments and are of good for the structure elucidation of these compounds.
Mechanism of the expulsion of oh from the [M  C2H4]+˙ ion from ethyl benzoate
Authors: Shapiro Robert H. , Tomer Kenneth B. , Caprioli Richard M. , Beynon John H.
Published: May 2005

Ion kinetic energy spectra of the esters C6H5C18OOC2D5 and C6H5COOC2D5 show that the ion formed by loss of C2D4 from the molecular ion has the deuterium atom attached to the carbonyl oxygen atom. Transfer of this deuterium to the other oxygen can only take place via exchange reactions involving the ortho‐hydrogen atoms and requires at least two complete rotations of the side‐chain.
Mass‐spectra of the phenyl‐cyclohexadiene‐isomers
Authors: Braun A. M.
Published: May 2005

Three basically different paths of fragmentation are evident from the mass spectra of the phenyl‐cyclohexadiene isomers.
The expulsion of OH˙ from the [M  C2H4]+˙ ion from ethyl benzoate: Ring‐deuterated compounds
Authors: Shapiro R. H. , Tomer K. , Beynon J. H. , Caprioli R. M.
Published: May 2005

Mass spectra and ion kinetic energy (IKE) spectra of o‐, m‐ and p‐d1 ethyl benzoates have given further information on the loss of OH˙ and OD˙ from the [M  C2H4]+˙ ions. The ‘metastable peaks’ in the mass spectra give information on fragmentations in the field‐free region following the electric sector; the IKE spectra give information on fragmentations in the field‐free region preceding this sector. Transfer of hydrogen and deuterium from the ortho‐positions on the ring to the carboxyl group can occur, but scrambling of ring hydrogens does not take place. A sample of o‐d1 benzoic acid was also examined and confirmed that similar transfer reactions occur in this compound too.
Electron‐impact promoted fragmentation of alkyl‐N‐(1‐phenylethyl)‐carbamates of primary, secondary and tertiary alcohols
Authors: Pereira W. E. , Halpern B. , Solomon M. D. , Duffield A. M.
Published: May 2005

The mass spectra of twenty N‐alkyl‐(1‐phenylethyl)‐carbamates derived from primary, secondary and tertiary alcohols have been investigated using deuterium labeling and high resolution mass spectrometry. These derivatives are suitable for the determination of the isotopic purity of primary and secondary, but not of tertiary alcohols. Several of the primary and secondary alcohol derivatives yield an ion formally equivalent to the product ion of a McLafferty rearrangement. Deuterium labeling established, however, that the usual site specificity associated with the McLafferty rearrangement process was lacking in these carbamate derivatives. In addition a double hydrogen rearrangement process was observed in the mass spectra of several of the carbamates derived from tertiary alcohols.
Studies on the mass spectra of 6‐methylthiopurine and its C‐and N‐methyl derivatives
Authors: Deutsch Joseph , Neiman Zohar , Bergmann Felix
Published: May 2005

6‐Methylthiopurines which bear a 9‐NH‐ or a 9‐NCH3‐group (class A) form an [M—1]‐ion with much higher abundance than do the 1‐, 3‐, or 7‐methyl derivatives (class B). The higher stability of the [M—1]‐ion in class A may be explained by ring closure to N‐7.

Methyl radicals are cleaved from N‐, but not from S‐ or C‐methyl groups, with the exception of the 7‐methyl derivative, in which the S‐CH3‐group can also split off a methyl radical. The methylthio group may lose all of the following fragments: S, SH, SCH, SCH2 and SCH3. In the remaining purine skeleton, in general first the pyrimidine and subsequently the imidazole ring breaks down with elimination of HCN.
Spectres de masse de phosphonates diméthyliques dérivés du norbornane, du norbornéne et du nortricyclane
Authors: Callot Henry J. , Benezra Claude
Published: May 2005

Les spectres de rnasse de phosphonates diméthyliques (I à X) dérivés du norbornane, du norbornène et du nortricyclane ont été étudiés. La fragmentation des isoméres endo et exo est trés comparable (seules les intensités des pics varient légèrement) sauf pour les dérivés saturés I et II où l'orientation du groupe P(O)(OCH3)2 inhence les coupures. Les spectres des dérivés du norbornène III et IV et du composé nortricyclique isomère IX sont très différents. La fragmentation des phosphonates I à X est dominée par la localisation de la charge sur le fragment phosphoré.
Elektronenstoß‐induzierte Fragmentierung von 1,2,3,‐Thiadiazolen
Authors: Zeller K.‐P. , Meier H. , Müller Eu.
Published: May 2005

Die Massenspektren einiger alkyl‐, aryl‐, acyl‐ und aroylsubstituierter 1,2,3‐Thiadiazole und des Benzothiadiazols werden mitgeteilt und interpretiert. Nach der Abspattung von N2 aus dem Molekiilion erleidet das [M—N2]+.‐ion eine Art WolRsche Umlagerung zu einem Thioketen‐Ionen‐Radikal. Ais Beweis wird die Bildung von Fragmentionen angefiihrt, die eine solche Umlagerung voraussetzen. Außerdem wird die Eliminierung von S bzw. ·SH aus dem nicht ungelagerten [M—N2]+.‐Ion diskutiert.
Mass spectrometry in structural and stereochemical problems—CXCIX Contrasting fragmentations of singly‐ and doubly‐chargedo‐,m‐ andp‐hydroxyalkylphenones and their trimethylsilyl ethers
Authors: Smith Grant Gill , Djerassi Carl
Published: May 2005

High resolution mass spectrometry, metastable defocusing and deuterium labeling of trimethylsilyl (TMS) ethers have been used to study the electron‐impact induced fragmentations ofo‐,m‐andp‐hydroxyalkylphenones and their TMS ether derivatives. These derivatives have proven useful in contrasting the fragmentation patterns of singly‐ and doubly‐charged ions because of the competing fragmentations: α‐cleavage and a McLafferty rearrangement from the ketone moiety and methyl cleavage from the TMS group. A proximity effect was responsible for a markedly increased methyl radical loss from theo‐TMS ether. This fragmentation was minor with them‐andp‐isomers. Significantly intense doubly‐charged ions were formed from ketonic cleavage and by the loss of a TMS methyl radical. The sequence of fragmentation depended on the size of the alkyl group attached to the ketone carbonyl. There was no evidence found for a McLafferty rearrangement occurring from the doubly‐charged molecular ion of the TMS ethers of the hydroxyalkylphenones but the rearrangement occurred from the doubly‐charge molecular ion ofbis‐3‐(1‐oxopentyl)‐4‐hydroxy‐phenyl‐methane and, of course, from the singly charged [M]+.Thebis‐p‐hydroxyphenylmethane derivatives were studied in an effort to increase the intensity of the doubly‐charged ions as it was expected that the charges would be separated by a longer distance.
The mass spectra of benzamide and thiobenzamide
Authors: Holmes J. L. , Benoit F.
Published: May 2005

The mass spectra of benzamide, thiobenzamide and their N‐d2 analogues have been studied In addition to fragmenting by simple bond cleavages the molecular ions dissociate partly from their imide forms. Equilibration or ‘scrambling’ of ortho ring hydrogen atoms with amide hydrogen did not occur in benzamide but such exchange must take place in the thiocompound whose fragmentation behaviour is very complex. Neither labelled compound produced the label‐retaining benzoyl (thiobenzoyl) cation which has been the subject of much interest in the mass spectrum of O‐d1 benzoic acid.
Mass spectrometry in structural and stereochemical problems—CCIV. Spectra of hydantoins II. Electron impact induced fragmentation of some substituted hydantoins
Authors: Corral Reneé A. , Orazi Orfeo O. , Duffield A. M. , Djerassi Carl
Published: May 2005

The mass spectral decomposition modes of hydantoin and derivatives containing alkyl and phenyl substituents have been investigated using isotopic labeling techniques. The loss of carbon monoxide from the molecular ions of these compounds was shown to preferentially involve the C‐4 carbonyl group. Other fragmentation processes characteristic of the hydantoin ring system and the effect on this of alkyl and phenyl substitution are described.
The mass spectra of some s‐triazolo[4,3‐a]pyrazines
Authors: Potts K. T. , Brugel E.
Published: May 2005

s‐Triazolo[4,3‐a]pyrazine underwent decomposition by loss of nitrogen from its molecular ion whereas in the 3‐alkyl derivatives the corresponding alkyl cyanide was eliminated from the 5‐membered ring. The introduction of a carbonyl or thiocarbonyl group into the 3‐position resulted in predominant loss of the triazole ring in the fragmentation process; however, with a 3‐amino substituent, the first fragment eliminated from the molecular ion was cyanamide. Methyl substitution in the 6‐membered ring resulted in the formation of ring expanded ions. On phenyl substitution, however, an interesting 1,2‐phenyl migration was observed. The mass spectra of several analogous s‐triazolo[1,5‐a]pyrazines are also described.
Carbon monoxide expulsion on electron‐impact: Hybrid fragmentation of α‐keto hemithioketals
Authors: Fenselau Catherine , Chandler H. A. , Pyles M. , Sander D. L. , Robinson C. H.
Published: May 2005

The fragmentation pattern and mass spectrum of 1‐(ethylene‐1′‐oxy‐2′‐thio)‐cyclohexan‐2‐one differ markedly from those of the related mono‐functional cyclohexane derivatives, cyclohexanone and (ethylene‐1′‐oxy‐2′‐thio)‐cyclohexane. This investigation delineates facile expulsion of carbon monoxide as the major hybrid fragmentation. The possibility of ring recyclization accompanying the expulsion is discussed.
Electron‐impact studies—LX Negative‐ion mass spectrometry of functional groups skeletal‐rearrangements in aryl nitro compounds
Authors: Bowie J. H.
Published: May 2005

The molecular anions of nitrobenzenes containing an electron‐withdrawing substituent eliminate NO· via a skeletal rearrangement process in the order ortho > para > meta. An ortho substituted nitrobenzene may eliminate a neutral molecule after the loss of NO· Hydrogen‐rearrange‐ment processes, hydrogen‐scrambling processes, and unusual concerted eliminations are noted in certain spectra. Isomeric nitrobenzenes are generally more readily differentiated by negative‐ion than positive‐ion mass spectrometry.
Ortho effect: The fragmentation of isopropyl 2‐hydroxychlorocarbanilates
Authors: Still Gerald G.
Published: May 2005

The mass spectra of isopropyl 2‐hydroxychlorocarbanilate indicate a preferential ortho intramolecular rearrangement which yields a chloro 2‐benzoxazolinone intermediate ion. A com‐parison of the fragmentation of ortho, meta and para hydroxy analogs of isopropyl 3‐chlorohydroxy‐carbanilate indicates the existence of an ‘ortho effect’ during the fragmentation of isopropyl‐chloro 2‐hydroxycarbanilates.
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

The 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.
The loss of Mė from the stilbene molecular ion. A reassessment
Authors: Bowie J. H. , White P. Y.
Published: May 2005

The recent report by Güsten, Klasinc, Marsel and Milivojevic has led us to critically review our earlier description of the loss of a methyl radical from the stilbene molecular ion.
Valency changes of sulphur in the mass spectra of sulphones
Authors: Soothill Rayner J. , Williams L. R.
Published: May 2005

The 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

o‐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

Das 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

The 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

The 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

Ionization 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

Metastable 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

Comparative 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.
Oxygen migration in primary nitroalkenes under electron‐impact
Authors: Carney Robert L.
Published: May 2005

Several primary nitroalkenes have been shown to undergo migration of oxygen to the carbon‐carbon double bond during mass spectrometric fragmentation. The oxocarbonium ion species which result are rationalized as arising through cleavage of ionized epoxide intermediates.
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

The 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

The 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

Sodium 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

Die 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

The 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

An 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

The 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

The 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

With 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

The 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

Collisional 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.
Field desorption mass spectrometry with indirect heating of the emitter
Authors: Winkler H. U. , Beckey H. D.
Published: May 2005

In field desorption mass spectrometry it is in many cases more expedient to heat the field anode indirectly by i.r.‐radiation instead of the usual method of electric heating to achieve higher relative molecular ion intensities.
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

The 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.
A novel rearrangement reaction in doubly charged ion mass spectra of acetophenone derivatives
Authors: Sakurai Hiroshi , Tatematsu Akira , Nakata Hisao
Published: May 2005

A novel rearrangement reaction for a methyl group is found in doubly charged ion mass spectra of p‐substituted acetophenone derivatives. The driving force for the reaction is discussed.
Ionisation and appearance potentials in structure analysis. A review
Authors: Jalonen Jorma , Pihlaja Kalevi
Published: May 2005

The suitability of mass spectrometric IP and AP measurements for different structural determinations has been critically considered and the pertinent literature reviewed.
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

Semi‐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

Les 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

Studies 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

An 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

The 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

The 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

The 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

Fragmentations 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

Die 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

The 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.
Mass spectrometry of heterocyclic compounds. V—Substituent effects on the fragmentation pathways of 3,5‐diphenyl‐1,2,4‐oxadiazole derivatives
Authors: Selva A. , Zerilli L. F. , Cavalleri B. , Gallo G. G.
Published: May 2005

The 70 eV mass spectra of a number of derivatives of 3,5‐diphenul‐1,2,4‐oxadiazole substituted either in the 5‐phenyl (fifteen) or in the 3‐phenyl (four) position, have been studied using exact mass measurements and metastable determinations by the defocusing technique. The substituent effects on the heterocyclic cleavage are not very important for electron‐withdrawing and weak electron‐donating groups. The main cleavage is the formal retro 1,3‐dipolar cycloaddition with the positive charge retained by the C7H5NO (orYC7H4NO in the case of the 3‐substituted derivatives) fragment specifically containing the 3‐phenyl, as oreviously observed for 3,5‐diphenyl‐1,2,4‐oxadiazole using labelling experiments. Two other minor primary processes leading to benzoyl and nitrile ions, both containing the 5‐phenyl, become important in the case of the electron‐donating substituted compounds. Correlation of the abundance of these fragmednts and of the molecular ions with σ+ (para) Brown constants is discussed. Proximity effets are shown by some ortho derivatives.
Energetische Betrachtungen zur Intramolekularen Solvatisierung von Ionen bei der Elektronenstoss‐Induzierten Fragmentierung von α,ω‐Bis‐(Trimethylsilyl)‐Äthern
Authors: Köppel Claus , Schwarz Helmut , Bohlmann Ferdinand
Published: May 2005

Es wird mit Hilfe von AP‐Messungen gezeigt, daß die stabilen [M – CH3]+‐Ionen aus α,ω‐Bis‐(Trimethylsily)‐äthern des Typs TMSO(CH2)nOTMS (n = 2 bis 7) keine cyclische Struktur besitzen.
Application of the indo molecular orbital method to ortho effects in mass spectra. Cleavage of cis‐β‐methoxystyrene
Authors: Kao Jar‐Lin , Parker Carol E. , Bursey Maurice M.
Published: May 2005

The principal fragmentation of the cis‐β‐methoxystyrene molecular ion is loss of the methyl group. Although this compound has a π system similar to that of phenyl acetate, the substituent effect of a strongly electronegative ortho substituent is insignificant for this fragmentation; but for the same substitution in phenyl acetate, it had been shown to be important. The INDO method was used to show that bond orders confirm the lack of the substituent effect in the cis‐β‐methoxystyrene system.
Electron‐impact mass spectrometry of Nuphar alkaloids
Authors: LaLonde Robert T. , Wong Chun F. , Woolever John T. , Auer Egmont , Das Kala C. , Tsai Amy I‐M.
Published: May 2005

Principal peaks in the mass spectra of deoxynupharidine are accounted for on the basis of high resolution mass spectrometry and peak shifts in the mass spectra of deoxynupharidine‐4‐d1 and deoxynupharidine‐6β, 7β‐d2. Cleavage of the quinolizidine ring system of deoxynupharidine occurs predominantly in ring A, giving m/e 136, 107, 98, 94 and 81. The origins of the family of ions [M — alkyl]+ and m/e 178 are considered. A comparative survey is made of the occurrence of these ions, and others, in the mass spectra of piperidine, quinolizidine and thiospirane types of Nuphar alkaloids. Attention is directed toions useful in distinguishing structural types.
Electron‐impact and thermal degradation of Rhodamine F5G chloride and related compounds
Authors: Davie Elizabeth , Morris John H. , Smith W. Ewen
Published: May 2005

The mass spectra and thermal decomposition of Rhodamine F5G hydrochloride have been studied in detail. Fragmentation schemes are presented which show that fragmentation in the mass spectrometer involves principally the substituents on the 9‐phenylxanthhydrol nucleus. Mass spectral studies of the related compounds Rhodamine B500 hydrochloride, Rhodamine F5G hydroxide and Rhodamine F5G dihydrogen phosphate are also reported. The thermal decomposition of Rhodamine F5G hydrochloride leads to initial loss of ethyl chloride and formation of the zwitterion which rearranges at higher temperature to a lactone. The further pyrolysis has also been studied.