bluuebunny/crossref_metadata_2025_split huggingface dataset:
Substituent effects on 13C and 15N chemical shifts in triazenes studied by principal components multivariate data analysis
Authors: Dunn W. J. , Lins C. , Kumar G. , Manimaran T. , Grigoras S. , Edlund U. , Wold S. 
Published: May 2005

AbstractPrincipal components analysis was applied to the 13C and 15N chemical shift data on a series of fifteen 1‐(para‐substituted‐phenyl)‐3‐acetyl‐3‐methyltriazenes. It was found that the halogen‐substituted triazenes formed a class, based on substituent effects, which was different from the remaining eleven triazenes. A one‐component model described the halogen class, whereas a two‐component model was necessary for a description of the second class. In the second class, substituents tended to cluster to form groups depending on their electronic character.
Phosphorus‐containing groups in analyses of carbon‐13 chemical shifts of 1‐hetera‐4‐cyclohexanones
Authors: Hirsch Jerry A. , Banasiak Kenneth 
Published: May 2005

AbstractThe 13C NMR chemical shifts of a series of phosphorinanes and the corresponding 4‐phosphorinanones have been evaluated using ‘double difference’ plots. Most of the compounds fit the same linear relationships for the carbons alpha and beta to the hetera group previously found for the analogous sulfur, oxygen and nitrogen six‐membered heterocycles, suggesting that these phosphorus compounds possess similar chair conformations. For the carbons gamma to the hetera group, the plots suggest that there are transannular interactions between the trivalent phosphine groups and the carbonyl group, similar to that previously observed for the sulfide group. In these 1‐hetera‐4‐cyclohexanones, transannular interactions appear whenever a lone pair of electrons on a second‐row heteroatom is present in the proper conformation for interaction with the carbonyl group.
The structural dependence of vicinal 13C13C coupling constants in s‐cis‐butane and cis‐butane
Authors: Klessinger Martin , Cho Jung‐Hyuck 
Published: May 2005

AbstractThe dependence of three‐bond 13C‐13C couplings of cis‐butane and cis‐butene on the valence angle, the torsional angle of the methyl groups and methyl and methylene substituents is discussed on the basis of INDO‐SCPT calculations. The results support the interpretation of the experimental couplings between the bridgehead carbons of bicyclic hydrocarbons based on a multiple‐path mechanism.
A mass‐spectrometric investigation of the radiolysis of methane by reactor radiation
Authors: Scott W. M. , Wilson H. W. 
Published: May 2005

AbstractAn ‘on‐line’ mass spectrometer technique which permits the examination of the effects of radiation at short times has been used to study the radiolysis of methane by reactor radiation. The mass spectrometer used was the AEI MS‐10. The experiments were carried out using the UTR‐100 reactor at East Kilbride and the results using highly purified methane and methane with radical scavangers are described. With pure methane at 0·25% conversion, G‐values of 0·36, 0·24, 0·07 and 0·03 were calculated for C3H8, C4H10, C5H12 and C6H14 respectively. No pressure‐dependent reactions were observed in the pressure range 50 to 135 torr. The effects of radical scavengers were investigated and irradiation of methane containing 1 to 2% ethylene gave G‐values for C2H6, C3H8, n‐C4H10, iso‐C4H10, C5H12 plus C6H14, C2H2, C3H6, C4H8 and C5H10 of 1·33, 2·02, 2·03, 0·35, 0·34, 0·30, 0·37, 0·90 and 0·31. The effects of adding 1 to 2% propylene and 1 to 2% oxygen were also examined and the results are described in the paper. Experiments with smaller quantities of oxygen emphasize the importance of removing all oxygen from the system before radiolysis begins. The paper then goes on to discuss in some detail the processes involved in the radiolysis of methane and concludes with suggestions for future work.
The mass spectra of carboxylic acids—I: Fragmentation mechanisms in maleic and fumaric acids and related compounds
Authors: Benoit F. , Holmes J. L. , Isaacs N. S. 
Published: May 2005

AbstractThe mass spectra of maleic acid, maleic acid‐2,3‐d, fumaric acid and fumaric acid‐2,3‐d have been examined and fragmentation mechanisms are proposed for these compounds. The molecular ion of the cis‐acid fragments via H atom transfer from one carboxyl group to the other followed by loss of CO2. The trans acid does not fragment significantly by this route and the former effect may be characteristic of molecules containing two carboxyl groups cis‐oriented to each other. This hypothesis was successfully tested by examining the mass spectra of citraconic, itaconic and phthalic acids. Itaconic and mesaconic acids show some of the fragmentation characteristics of fumaric acid.
Electron‐impact studies—LI: Hydrogen randomization in the stilbene molecular ion
Authors: Donaghue P. F. , White P. Y. , Bowie J. H. , Roney B. D. , Rodda H. J. 
Published: May 2005

AbstractHydrozen randomization precedes the formation of M+·  H· and M+·  CH3· species from the stilbene molecular ion at 15 eV. The carbon atom involved in the M+·  CH3· elimination originates randomly from the whole molecule. The [M  15] ion (m/e 165) in the spectra of stilbene and 9,10‐dihydrophenanthrene is produced from a common ion.
Routine, accurate mass measurement up to m/e 1700 using vapor‐deposited silver bromide plates
Authors: Hignite C. , Biemann K. 
Published: May 2005

AbstractThe utility of photoplate recording of high resolution mass spectra for routine, accurate mass measurement is extended to mass 1700 (and probably beyond) by the use of evaporated silver bromide plates. Data illustrating the accuracy obtainable and the dynamic range are presented.
The problem of the azatropylium ion: Hydrogen elimination from the molecular ion of γ‐picoline
Authors: Neeter R. , Nibbering N. M. M. , De Boer Th. J. 
Published: May 2005

AbstractComparison of the mass spectrum of γ‐picoline with that of analogues, specifically deuterated in the methyl group, the ring or both, has shown that the molecular ion loses the α,β and methyl hydrogen atoms (ω‐hydrogen') in the ratio 1.43: 1: 1. 13. The same trend is found for the elimination of HCN from the molecular ion. Moreover, a value of 1.52 is found for the isotope effect, expressing the favoured loss of H over D, irrespective of its position.
Combined gas chromatography‐mass spectrometry of the inositol trimethylsilyl ethers and acetate esters
Authors: Sherman William R. , Eilers Nancy C. , Goodwin Sally L. 
Published: May 2005

AbstractEach of the inositol diastereomers have been subjected to low resolution gas chromatography‐mass spectrometry as their hexa‐O‐trimethylsilyl (TMSi) ethers and as their hexaacetyl esters. The TMSi ethers of the inositols each possess a unique spectrum consisting of the same ions occurring with remarkable variation in intensity. This variation, which is much greater with the inositol TMSi ethers than in the spectra of the inositol acetates, is presumably an expression of the stereochemistry of each isomer exaggerated by the bulky TMSi groups. Using TMSi‐d9, labeling as well as ring labeling with deuterium we identified several fragment ions which are characteristic of the cyclitols. The spectra of the TMSi inositols are compared with the spectra of other TMSi carbohydrates.Two main series of fragmentation processes are observed in the inositol hexaacetates. With the aid of acetyl‐d3 labeling each of these series were found to divide into two more pathways consisting of ions of the same m/e values but of different structures. These pathways are compared with similar pathways observed in other acetyl carbohydrates.A method is described for the direct conversion of TMSi ethers to acetate esters which has potential usefulness in natural product studies.
Reactions in the source of a mass spectrometer: The mass spectrum of 1‐chlorobenzotriazole
Authors: Thomas C. B. 
Published: May 2005

AbstractThe mass spectrum of 1‐chlorobenzotriazole contains ions derived from benzotriazole, a product of an exchange reaction with water in the source of the mass spectrometer. Relatively intense ions derived from iodine, iodine monobromide and other inter‐halogen compounds are also observed. These species are produced by oxidation of involatile halide coatings in the source region by 1‐chlorobenzotriazole. It is suggested that anomalous peaks produced by oxidation‐reduction reactions in the source may be expected in the spectrum of any organic oxidant.
Mass spectrometry of onium compounds—IV: Diazonium salts
Authors: Undheim Kjell , Thorstad Olav , Hvistendahl Georg 
Published: May 2005

AbstractThe zwitterions of diazotized ortho and para aminophenol are very volatile and give strong peaks in the mass spectra corresponding to the molecular ion. The m‐isomer, which cannot be stabilized through a simple quinonoid structure, gives rise to a complex spectrum through decomposition and coupling reactions. The zwitterions of diazotized anthranilic and sulphanilic acids did not give the molecular ion peak.
A small computer data system for low resolution magnetic deflection mass spectrometers
Authors: Plattner J. R. , Markey S. P. 
Published: May 2005

AbstractA small on‐line computer system for complete processing of low resolution magnetic deflection mass spectrometric data has been demonstrated. An interpolated mass scale accuracy of 200ppm was achieved for both repetitive (five or ten second cycle times) and single scan modes. Identification of m/e values above 1000 is possible with an accuracy of 500 ppm to m/e 3600. Mass scale assignments are time based and externally calibrated (pfa).
Field desorption mass spectrometry of amino acids
Authors: Winkler H. U. , Beckey H. D. 
Published: May 2005

AbstractThe mass spectra of some amino acids have been studied using the field desorption method. All amino acids yield molecular or quasi‐molecular ions, even in the case of arginine and cystine, where these ions cannot be detected with the electron‐impact (EI) or chemical ionization (CI) methods. The fragmentation is reduced as compared to EI, CI and FI.
Mass spectral studies on mesoionic imidazo [1,2‐a] pyrid‐2 and ‐3‐one derivatives
Authors: Anderson Wayne K. , Friedman Alan E. 
Published: May 2005

AbstractThe mass spectral fragmentation patterns for 1‐substituted derivatives of anhydro (3‐chloroacetyl‐2‐hydroxyimidazo[1,2‐a]pyridinium hydroxide) (Ia to Ie) and 2‐acyl substituted derivatives of anhydro(1‐benzyl‐3‐hydroxyimidazo[1,2‐a]pyridinium hydroxide) (IIa and IIb) are reported. In all cases the mass spectra may be interpreted on the basis of initial cleavage of the ‘carbonyl‐heteroatom’ bond of the mesoionic system, followed by fragmentation.
Electron‐impact and thermal fragmentation patterns of some perfluoroalkylene‐linked aromatic and heteroaromatic compounds
Authors: Cotter J. L. 
Published: May 2005

AbstractThe pyrolysis of some perfluoroalkylene‐linked aromatic and heteroaromatic polymer precursors and a poly(1,3‐phenylenehexafluorotrimethylene) has been studied using a combined pyrolysis‐gas chromatographic‐mass spectrometric method. Whereas the electron‐impact induced fragmentations of the polymer precursors are almost exclusively controlled by cleavage β to the aromatic or heteroaromatic ring, thermolysis of these compounds yields products whose formation is consistent with the occurrence of primary cleavage processes that are not confined β to the ring.
High‐resolution mass spectra of two α,β‐unssaturated γ‐dilactones
Authors: Kolsaker Per 
Published: May 2005

AbstractThe fragmentations of two α,β‐unsaturated γ‐dilactones in a mass spectrometer are studied. The main feature is conecutive carbon monoxide expulsions. Strong indication of ejection of a fragment C2O2 is presented, however. Masses were determined by the high resolution rechnique and metastable transitions were detected by defocusing. Corresponding deuterated dilactones were also studied to verify the fragmentation mechanism.
Elimination reactions of ions in the gas phase–I: Elimination of water and acetic acid in epimeric borneols and bornylacetates
Authors: Robbiani R. , Seibl J. 
Published: May 2005

AbstractLoss of water and acetic acid in the epimeric bornyl alcohols and acetates are shown to be analogous processes by specific 2H‐labelling. Among several competing mechanisms cis‐1,2‐elimination is the most important. Mctastable ion characteristics of this specific process exhibit some unusual features and its product is shown to have a different structure from that produced by the competing reactions.
Mass spectral studies on steroidal compounds—V: Rings B and A seco 5‐keto compounds in the cholestane series
Authors: Ahmad M. S. , Mushfiq M. , Ansari G. A. S. , Waris Miss F. 
Published: May 2005

AbstractThe mass spectra of several structurally related ring B seco 5‐keto compounds (I to VII) have been examined. The mass spectra of I, II, III and IV are conspicuous by an intense peak at m/e112(C7H12O) and those of V (highest mass peak at [M  CH3COOH]), VI and VII by a prominent peak at m/e 100 (C7H10O), which apparently results from McLafferty rearrangement involving 5‐keto function and an appropriate γ‐hydrogen at C‐8 and C‐11. This rearrangement, leading to the aforementioned ions, is of diagnostic value in the characterisation of such compounds. The mass spectrum of VIII exhibits a prominent ion peak at m/e 332 (C23H40O) resulting from McLafferty rearrangement involving the 5‐keto function and C2H. This offers an excellent means of differentiating between the isomeric acids (III and VIII). The fragmentation pathways suggested are supported by accurate mass measurement of the salient fragment ions and in some cases by appropriate metastable peaks.
Spectres de Masse de Derives de l'Atractyloside. Determination du Nombre de Substituants par Combinaison d'Acetylation et de Silylation
Authors: Defaye G. , Ulrich J. 
Published: May 2005

AbstractEn créant des dérivés différents suivant la fonction que l'on transforme, il est possible de dénombrer rapidement chacune de ces fonctions sur une molécule complexe du type hétéroside. Silylation de toutes les fonctions dans un premier temps suivie de l'acétylation des fonctions alcools et de la silylation des sulfates et acides dans un second temps. Des molécules d'atractylate, d'apoa‐tractylate et de gummiférine ont été étudiées de cette façon.
Carbon‐oxygen bond formation in the mass spectra of aryl methyl sulphones
Authors: Pratanata Miss I. , Williams L. R. , Williams R. N. 
Published: May 2005

AbstractUpon electron‐impact aryl methyl sulphones (I) rearranged to form aryl‐oxygen bonds. The mode of fragmentation of the intermediate ester (II) to give [aryl O]+ or [aryl OH]+ ions was found to be markedly influenced by the nature of the aryl substituent.
The mass spectra of substituted 2‐methylbenzophenones
Authors: Grimshaw James , Sell Charles S. , Haslett Reginald J. 
Published: May 2005

AbstractThe mass spectra of some methoxy and methyl derivatives of 2‐methylbenzophenone have been examined. Loss of a substituents from 3′‐and 4′‐positions as well as the previously known loss from 2′‐positions are important fragmentation processes. Thus, these fragmentations are of little use in locating substituents on benzophenones of unknown structure. Deuterium labelling shows the [M ‐ 1]+ ion from 3′,4,4′,5,5′‐pentamethoxy‐2‐methyl benzophenone to be due largely to loss of hydrogen from 2′‐ and 6′‐positions.
Mass spectrometry of antibiotic kikumycin A, B and related compounds
Authors: Takaishi Tetsuo , Suzuki Makoto , Tatematsu Akira 
Published: May 2005

AbstractThe structures of kikumycin A and B, antiviral amidine antibiotics, have been elucidated by means of low and high resolution mass spectrometry. Amino acid composition and their sequences were also clearly demonstrated by this technique. The evidence for the fragmentation of terminal amidines or amides of kikumycin derivatives and related synthetic compounds was represented by the elimination of ammonia or water from the molecular ions to give stable nitrile ions. Additionally, the participation of the iminol structure in the pyrrole‐2‐carboxamide portion of kikumycin A and B was confirmed by the fragment ions derived from their iminol tautomers.
The mass spectrometry of DT‐and monosubstituted biphenyls: Dependence of fragmentation patterns on position of substitution
Authors: Sheley Curtis F. , Patterson Robert T. 
Published: May 2005

AbstractThis paper describes the mass spectroscopy of a series of biphenyl derivatives substituted in the 2,2′, 4,4′ and 2 positions. The substitutent functional groups are carbomethoxy, carbothoxy, carboxylic acid and hydroxymethyl. In addition, some results are reported on the spectroscopy of the d5‐carboethoxy derivatives, the 2‐ and 2,2′‐αd2‐ hydroxymethyl derivatives and fluorene‐4‐methanol.The molecular ions of the 4,4′‐disubstituted biphenyl derivatives are far more stable than those of the 2,2′ isomers. It is also observed that the fragmentation patterns of these two sets of isomers are sharply different. Paradoxically, the 2‐substituted biphenyl derivatives give relatively stable molecular ions and their fragmentation patterns are frequently different from those of the corresponding 2,2′‐disubstituted biphenyls. The bulk of the evidence presented in this paper suggests that the usual sort of ‘ortho effect’ is not a significant factor in the fragmentation mechanisms proposed for the 2,2′‐disubstituted biphenyl derivatives.
Massenspektroskopische Fragmentierungsreaktionen: VI –Produktstabilität oder ‘lokalisierte Ladung’ als Konzept zur Deutung der Bruchstückbildung?
Authors: Budzikiewicz H. , Pesch R. 
Published: May 2005

AbstractAn Hand von Alkylaminen, die ω‐ständig eine zweite funktionelle Gruppe (O, S, Se) tragen, wird gezeigt, daß bei Ionisierung unterhalb des Ionisierungspotentials primärer Amine Ladungswanderung zum N, die schließlich zur Bildung von CH2NH2+ führt, nicht generell über die σ‐Bindungen, sondern über spezielle Mechanismen erfolgen kann. Zusätzlich wird das Fragmentierungsverhalten einfacher Methyl‐alkyl‐selenide beschrieben.
The mass spectrometric fragmentation of n‐benzylacetamide
Authors: Gilbert J. R. , Potter E. , Stace A. J. 
Published: May 2005

AbstractThe low energy mass spectra of N‐benzylacetamide have been recorded. The major fragmentations of the molecular ion are similar to those observed in the acetanilide spectrum. In addition, the secondary dissociation of the [C6H5CH2NH]+ ion by loss of HCN is shown to occur with transfer of the ‐N–H hydrogen to the ring.
Computer‐aided interpretation of mass spectra. Information on substructural probabilities form stirs
Authors: Dayringer Henry E. , Pesyna Gail M. , Venkataraghavan Rengachari , McLafferty F. W. 
Published: May 2005

AbstractThe capability of the ‘Self‐Training Interpretive and Retrieval System’ has been extended so that the compounds selected as providing the best match in each data class to the unknown mass spectrum are examined by the computer for the presence of each of 179 common substructural fragments. Stastical methods were used to evaluate the selectivity for identification of each substructure by each data class using a reference file of 18 806 spectra of different compounds. In tests using at least 373 unknown spectra for each of the substructures, with criteria that gave a mean reliability of 98.1%, the method averaged 49% recall, which corresponds to the identification of 2.55 substructures per unknown spectrum, as well as the normal “Self‐Training Interpretative and Retrieval System” match‐factor results, requires 68 s on a laboratory computer. The method is also available to outside users on an international computer network.
Computer‐aided interpretation of mass spectra. Increased information form characteristic ion
Authors: Dayringer H. E. , McLafferty F. W. 
Published: May 2005

AbstractThe characteristic ion data classes of the ‘Self‐Training Interpretive and Retrieval System’ have been modified to test the effect of number of ions, even‐and odd‐electron ion requirement, over‐lapping mass ranges and arithmetic combinations of the rankings found by several data classes. Statistical methods were applied to evaluate the performance achieved for 202 substructures using a reference file of 18 806 spectra of different compounds and testing at least 373 compounds for each substructure. A Linear combination of the new characteristic ion data classes gave 47% recall with 98% prediction reliability, a substantial improvement over the performance of the previous system. The use of overlapping mass ranges was the most important factor in the improved performance, increasing the recall for 42 of the substructures. Three examples illustrate the utility of the improved system.
Gas phase isomerization of \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm C}_{{\rm 10}} {\rm H}_{{\rm 14}} } \right]_{}^{_.^ + } $\end{document} ions generated from adamantanoid compounds
Authors: Majerski Zdenko , Karlović Gordana , Ðigaš Stjepan , Stefanović Duško 
Published: May 2005

Abstract\documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm C}_{{\rm 10}} {\rm H}_{{\rm 14}} } \right]_{}^{_.^ + } $\end{document} ions have been generated from a number of adamantanoid compounds, both by ionization and ionization followed‐by fragmentation. Metastable ion abundance ratios of competitive reactions indicate the decomposition of these ions from common structures in all cases.
Etude de la Fragmentation en Spectrographie de Masse de Spiropyrannes Benzodithioliques. Influence de la Position et de la Nature des Substituants
Authors: Derocque Jean Luc , Appriou Pierre , Guglielmetti Robert , Dürr Heinz 
Published: May 2005

AbstractNous reportons les spectres de 12 spiropyrannes benzodithioliques. Leurs cartes de fragmentation on été déterminées par étude des transitions métastables et par mesure à haute résolution. La fragmentation on de ces composés dépend de la nature et de la position des substituents et nos résultats sont comparés à ceux observés par action de la lumière et de la chaleur sur ces composés.
Hydrogen rearrangements of ionized propanoic acid and isomeric ions
Authors: McAdoo David J. , Witiak Dennis N. 
Published: May 2005

AbstractIonized propanoic acid and its enol isomer lose H˙ in both normal and metastable decompositions. These C3H6O2 ions lose their distinctness prior to undergoing metastable decomposition in the mass spectrometer. Deuterium labeling indicated that this results from the transfer of a β‐hydrogen to oxygen in the propanoic acid ion followed by rapid exchange of hydrogen and deuteriums between the α‐ and β‐carbons and slower exchange between the carbons and the oxygens. 3‐ and 5‐Membered ring hydrogen rearrangements are preferred over 4‐membered ring transfers. It is concluded that 1,2‐hydrogen shifts following removal of hydrogen from alkyl chains may sometimes cause site‐specific hydrogen rearrangements to appear non‐site specific.
Anchimeric assistance in the fragmentation of protonated glycol derivatives in a flowing afterglow
Authors: Schmitt Robert J. , Shapiro Robert H. 
Published: May 2005

AbstractA series of monomethyl, monoacyl glycols was protonated in a flowing afterglow system. In the subsequent fragmentation reactions acetic acid was found to be a better leaving group than methanol, but the acetoxy group was shown to participate in methanol expulsion under certain conditions. The effects of leaving group ability, anchimeric assistance, stereochemistry and steric hindrance on the fragmentation patterns of the protonated molecular ions are discussed.
The mass spectrometry of polychlorinated dibenzo‐p‐dioxins
Authors: Hass J. Ronald , Friesen Marlin D. , Hoffman Michael K. 
Published: May 2005

AbstractThe negative ion chemical ionization mass spectra of polychlorinated dibenzo‐p‐dioxins using oxygen, methane and methane/oxygen are reported together with their methane positive ion chemical ionization mass spectra and conventional electron impact spectra. The methane/oxygen negative ion chemical ionization mass spectra proved to be the most useful of the negative ion spectra for structure determination.