bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on morphine alkaloids—IX. The mass spectra of indolinocodeine and its derivatives
Authors: Abe K. , Onda M. , Okuda S.
Published: May 2005

The mass spectra of indolinocodeine and its derivatives have been determined. Some of the fragmentation pathways are discussed on the basis of high‐resolution mass spectrometry and deuterium labelling. Although basic fragmentation patterns for this series of compounds are similar to each other, the substituents in B‐ and/or C‐ring were found to determine the course of the fragmentation.
Mass spectra of cobalt carbonyl complexes
Authors: Gambino O. , Vaglio G. A. , Ferrari R. P. , Valle M. , Cetini G.
Published: May 2005

The mass spectra of the following acetylenic derivatives of Co2(CO)8 are reported: Co2(CO)6C2H2Co2(CO)6C 2,(CH3)2, Co2(CO)6 C2(CH2Cl)2, Co2(CO)6C2 (CF3)2, Co2(CO)2C2(C6H5)2 and Co2(CO)6C2(COOCH3)2. The effect of different C2RR′ on fragmentation modes is investigated. When R and R′ are aromatic groups, the major controlling factor is the stability of charged fragments; in other cases, it seems to be the loss of a stable neutral moiety. Transfer processes of alkoxylic groups are observed in Co2(CO)6C2(COOCH3)2, as well as in Co3(CO),9CCOOCH3, and Co3(CO)9CCOOC2H5. It is suggested that both cobalt and carbon atoms may be the migration sites.
Studies in chemical ionization mass spectrometry: 17‐hydroxy steroids
Authors: Michnowicz John , Munson Burnaby
Published: May 2005

The chemical ionization mass spectra of several hydroxy steroids were obtained using methane as the reactant gas. The spectra are much less complex than the electron ionization spectra and little fragmentation of the steroid nucleus is observed. The major fragment ions involve the loss of water from [M + H]+. A 3‐keto group in the steroids was characterized by an abundant [M + C2H5]+ ion. 5α‐ and 5β‐Dihydrotestosterone could be distinguished by their spectra, with H2 as the reactant gas by marked differences in amounts of [M + H]+, [M + H − H2O]+ and [M + H − 2H2O]+. Substituted 3α‐X‐, 17 β‐ol compounds, (X = Cl, Br) were also studied to obtain relative amounts of protonation at these sites.
Mass spectrometric comparison of ordinary and fully deuterated α‐ and β‐carotene
Authors: Svec W. A. , Harkness A. L. , Strain H. H. , Katz J. J.
Published: May 2005

The individual, deuterated, isomeric α‐ and β‐carotenes were isolated from the green alga, Scenedesmus obliquus, cultivated in D2O containing 99·7 to 99·8 atom percent deuterium. Mass spectroscopy showed that both the α‐ and β‐deuterio‐carotene preparations contained principally the fully deuterated pigment molecules (C40D56), small quantities of deuterated molecules with one proton (C40D55H) and yet smaller quantities of deuterated molecules with two protons (C40D54H2). From statistical calculations the deuterio‐carotene preparations also contained one to several isotopically‐substituted deuterio‐carotenes of each mass in the mass range 585 to 599 because of variation of the number of 13C and H atoms per molecule. The mass fragmentation of the deuterated pigments was analogous to that of the respective ordinary α‐ and β‐carotene. It indicated that the protons in the C40D55H and C40D54H2 molecules were distributed approximately randomly in various parts of the structure as in the terminal rings and in the ends and central portions of the polyene chain.
Cyclization of molecular ions: The mass spectrometric fragmentation of allene‐carboxylic esters
Authors: Liehr J. G. , Runge W. , Richter W. J.
Published: May 2005

A series of six 2,4,4‐substituted allenecarboxylic esters R1R2CCC(R3)COOAlk has been found to exhibit O‐Alkyl cleavage as the most prominent feature of both their 70 and 12 eV mass spectra. Loss of linearity of the allene system upon ionization, followed by conversion of the molecular ion to a 5‐membered cyclic isomer, is thought to induce this unusual mode of bond rupture. Oxygen‐migration from the ester function to C‐4 as is indicated by the subsequent decomposition of the [M — Alk] ions to [R1CO]+ and [R2CO]+ fragments can be taken as direct evidence in favour of this rationale.
Rearrangement of the benzyl benzoate molecular ion to lose H2O
Authors: Beynon J. H. , Caprioli R. M. , Shapiro R. H. , Tomer K. B. , Chang C. W. J.
Published: May 2005

The molecular ion of benzyl benzoate undergoes several decompositions, two of which are the loss of H2O and COOH·. To study these processes, the mass and IKE spectra of benzyl benzoate together with various deuterated benzyl benzoates and some of its isomers were studied. Evidence is presented to support the rearrangement processes of the molecular ion. A decomposition scheme is proposed to explain the observed transitions.
Migration of dimethylsilyl substituents upon electron‐impact: The fragmentation of methyl 12‐dimethylsilyloxyoctadecanoate
Authors: Hunneman D. H. , Richter W. J.
Published: May 2005

Fragmentation of the dimethylsilyl (DMS) derivative of methyl 12‐hydroxyoctadecanoate is found to be closely analogous to that of the previously studied trimethylsilyl (TMS) derivative, including migration of the silyl substituent from C‐12 to the ester carboxyl function. besides establishing comparable migratory aptitudes of the TMS and DMS substituents, details of several other processes were revealed by use of deuterium labelling of selected positions and compared with related fragmentation of simple long‐chain alcanoic esters.
Substituent effects in the field ionization mass spectra of acetophenones
Authors: Beckey H. D. , Migahed M. D.
Published: May 2005

Substituent effects in the electron‐impact and field ionization mass spectra of acteophenones are compared. No Hammett correlation could be found for the fragments formed on the surface of the field anode. A straight line log z/z0 versus σ+ was observed, however, for the metastable decomposition of para‐substituted acetophenones (and also some benzophenones). Meta‐substituted compounds did not yield such straight lines.
Mass spectra of the aminoisoquinolines and 5‐amino‐15N‐isoquinoline
Authors: Brown Ellis V. , Mitchell Stanley R.
Published: May 2005

The mass spectra of the isomeric aminoisoquinolines and 5‐amino‐15N‐isoquinoline are reported. In the aminoisoquinolines, the major fragmentation pathway was the loss of two molecules of HCN and a hydrogen atom to give the m/e 89 fragment ion. Two additional pathways culminating with this ion were observed. The mass spectrum of 5‐amino‐15N‐isoquinoline showed a preference of 4 to 1 for loss of HC15N (benzenoid amine group) over HC14N (heterocyclic nitrogen) from the molecular ion.
Dimethyl ketals of methylcyclohexanones as fragmentation‐directing derivatives
Authors: Manni Peter E. , Cooper Ralph D. , Hardesty Clifford L.
Published: May 2005

The mass spectra of dimethyl ketal derivatives of cyclohexanone and the 2‐, 3‐ and 4‐methylcyclohexanones are discussed relative to their usefulness in indicating the point of alkyl substitution. Major fragments in the spectra (m/e 101 and m/e 115) arise by α‐cleavage, hydrogen rearrangement and further cleavage to give even‐electron species. The spectra yield structural information equivalent to that obtained from the corresponding ethylene ketals. The ease of preparation of dimethyl ketals and the mildness of reaction conditions relative to ethylene ketals warrant further exploitation of dimethyl ketals as fragmentation‐directing derivatives in mass spectrometry.
Ring expansion and hydrogen scrambling in the molecular ion of 3‐methylthiophene
Authors: Wakkers P. J. M. , Janssen Matthijs J. , Weringa W. D.
Published: May 2005

The ratio [M  D]/{[M‐D] + [M  H]} in the 70 eV mass spectra of six deuterated 3‐methylthiophenes has been determined. From these values the mole fractions of the molecular ions that lose hydrogen atoms specifically from the various positions of the molecule were calculated, as well as the mole fraction in which the hydrogen atoms are fully scrambled before hydrogen elimination. It appears that hydrogen atoms are mainly lost from a fully scrambled [C5H6S]+· ion and from the α‐position of the original molecular ion. A deuterium isotope effect of 1·60 to 1·72 was calculated for the hydrogen elimination. The reaction was also studied at low electron energies. In order to determine the degree of scrambling in the [C5H5S]+ ions, some decomposition reactions of this ion were investigated.
Studies in organic mass spectrometry—XI. The fragmentation of hop bitter acids derivatives having a five membered ring structure
Authors: Cant E. , Vandewalle M. , Verzele M.
Published: May 2005

The mass spectra of the hops derived humulinic acids, isohumulones and hulupones are discussed. The fragmentations are in accordance with those found for model compounds.
The mass spectra of alkylbenzenes—II. The formation of [M  methyl]+ from tri‐ and tetra‐methylbenzenes
Authors: Dawson R. M. , Gillis R. G.
Published: May 2005

A study of the [M  methyl]+ ion in the mass spectra of ring‐deuterated tri‐ and tetramethylbenzenes has confirmed the partial randomisation of hydrogen and deuterium atoms observed by other workers. The results can be explained by postulating randomisation of the peripheral entities, followed by several cycles of ring expansion and contraction, prior to fragmentation.
The mass spectra of some 7‐methoxycoumarin derivatives with differing 6‐substituted C5 isoprenoid sidechains
Authors: MacLeod J. K.
Published: May 2005

The mass spectra of several biogenetically and chemically inter‐related coumarins (I to XVII) have been examined, and fragmentation pathways proposed on the basis of metastable evidence and deuterium labelling studies. The particular modification of the isoprenoid sidechain present in each compound directs fragmentation and gives rise to characteristic mass spectral cleavage patterns which may be useful for structural elucidation.
Mass spectral studies on steroidal compounds—I: Steroidal 6‐one ethylene acetals
Authors: Ahmad M. S. , Ansari G. A. S.
Published: May 2005

The mass spectra of several steroidal 6‐one ethylene acetals have been examined. The spectra of I and II are conspicuous by an intense [M — 55] peak. This differentiates them from other acetals reported in the present study. The acetals III, IV, V, VI, VII and VIII show the expected behaviour related to the acetal IX. The fragmentation pathways suggested are supported by accurate mass measurement of the salient fragment ions and in some cases also by appropriate metastable peaks.
Mass spectral studies on steroidal compounds—II: 7a‐aza compounds in the cholestane series (ring Bε‐lactams)
Authors: Ahmad M. S. , Mushfiq M.
Published: May 2005

The mass spectra of four structurally related 7a‐aza compounds in the cholestane series have been examined. These spectra are conspicuous by the presence of a fragment ion peak at m/e 222 (C15H28N). which can be of diagnostic value in characterisation of such ε‐lactams. The fragmentation pathways are supported by accurate mass measurement of the salient fragment ions and in some cases by appropriate metastable peaks.
An unusual rearrangement observed in the mass spectra of several 1‐alkyl‐2‐substituted‐5‐nitroimidazoles
Authors: Van Lear George E.
Published: May 2005

The mass spectra of several l‐alkyl‐2‐substituted‐5‐nitro imidazoles exhibit prominent rearrangement ions corresponding to the loss of CnH2nO from the molecular ion. The effect on this rearrangement upon variation of the group at position 2 is discussed.
Mass spectrometry of 1,1′‐diacetylferrocene and 1,1′‐dipropionylferrocene: Evidence for intraannular interaction between alkanoyl substituents
Authors: Sheley Curtis F. , Fishel Derry L.
Published: May 2005

The mass spectra of 1,1′‐diacetylferrocene, 1,1′‐dipropionyl ferrocene and their deuterium and Fe57 isotope labeled analogs are herein reported and discussed. Fragmentation pathways are established and evidence is presented that in the process of fragmentation there is extensive interaction between substituents on the two ferrocene rings. This process apparently has little precedent in the mass spectrometry of ferrocene derivatives. Specifically, the experimental results suggest the simultaneous elimination of two molecules of carbon monoxide, or in another case, of carbon monoxide and ethylene from ions produced in the mass spectrometry of the above compounds.
Mass spectral studies of unsaturated carboxylic acids—I: Some cyclic and acyclic βγ‐unsaturated acids
Authors: Alexander R. G. , Bigley D. B. , Todd J. F. J.
Published: May 2005

The mass spectra of a series of βγ‐unsaturated cyclic and acyclic carboxylic acids are reported. Metastable ion studies and precise mass measurements have been employed in demonstrating that the ten compounds studied conform to one or other of two generalised fragmentation pathways.
Positive chemical ionization mass spectra of polycyclic chlorinated pesticides
Authors: Biros Francis J. , Dougherty Ralph C. , Dalton John
Published: May 2005

Methane chemical ionization (CI) mass spectra for a series of ten polycyclic chlorinated insecticides and metabolites have been examined. In all cases except heptachlor epoxide the base peak corresponded to elimination of Cl, or OH from the molecule ion. In the spectrum of heptachlor epoxide the [M + H]+ and [M − Cl]+ clusters were of approximately equal intensity. The CI spectra were remarkably simple, invariably less complex than the corresponding electron‐impact (EI) mass spectra and the intensity of the ions with high information content, e.g. [M − CI]+ was uniformly high. All of these features are important to the analytical potential of these studies. Retro Diels‐Alder (RDA) fragments were observed for the chlordanes, aldrin, isodrin, nonachlor and heptachlor epoxide. The reported preliminary data suggest that the relative intensity of RDA ions in CI mass spectra may be useful in establishing molecular configurations.
Negative chemical ionization mass spectra of polycyclic chlorinated insecticides
Authors: Dougherty Ralph C. , Dalton John , Biros Francis J.
Published: May 2005

Negative ion mass spectra obtained under chemical ionization conditions (NCI) employing methane, isobutane or methylene chloride as the enhancement gas are presented for a series of chlorinated polycyclic insecticides. All of the compounds examined except 1‐hydroxychlordene yielded molecular anions of substantial relative abundance (6 to 39%). The most significant features of the spectra are the prominent peaks at masses greater than that of the molecule ion formed via ionmolecule association reactions. Peaks representing association of the parent molecule with ionic species such as H−, O−, OH−, Cl−, H2OCl−, HCl2−, ClO− and Cl3− were observed in some cases. The base peak in all spectra was associated with the isotopic group of the [M + Cl]− on if contributions from other negative, even electron ions of low mass values present in high concentrations (Cl−, H2OCl− Cl2− and HCl2−) are neglected. Fragmentation processes were limited to elimination reactions involving loss of combinations of the even electron neutral species H, Cl and HCl. In addition, fragmentation resulting from a nucleophilic radical displacement of Cl by O− from the parent molecule was observed in all cases except 1‐hydroxychlordene when the source was modestly wet (methane as reactant gas). NCI mass spectra of polycyclic chlorinated pesticides are reproducible, intense, interpretable in terms of classical carbanion chemistry and thus may have important analytical utility, particularly when used in conjunction with positive electron‐impact and chemical ionization mass spectral methods and selective use of different enhancement gases.
Mass spectrometry of organic compounds in the group V elements—II: Branched chain aliphatic derivatives
Authors: Kostyanovsky R. G. , Plekhanov V. G. , Elnatanov Yu. I. , Zagurskaya L. M. , Voznesensky V. N.
Published: May 2005

The behaviour of compounds I to XII under electron‐impact (electron voltages 30 and 12 eV) was investigated. The abundance of the ions characteristic of amines was shown to decrease drastically with an increase of chain branching in alkylphosphines. Comparison of the spectra of VII and X led to the conclusion that the unshared electron pair of phosphorus does not affect the fragmentation. The main peaks in the spectra of phosphines corresponded to hydrocarbon fragments. The origins of the main fragment ions were confirmed by metastable peaks.
Mass spectra of lincomycin, lincomycin analogs and degradation products
Authors: Kagan Fred , Grostic Marvin F.
Published: May 2005

The principal ions observed in the mass spectra of lincomycin hydrochloride, some of its analogs and two degradation products are discussed. Lincomycin‐related compounds can be characterized by examination of the molecular ion and four other ions. Plausible mechanistic interpretations of these ions are presented.
The study and characterization of nucleosides by mass spectrometry—I: The mass spectra of pyrimidine 2,2′‐anhydronucleosides and their derivatives
Authors: Westmore J. B. , Lin Denis C. K. , Ogilvie K. K. , Wayborn H. , Berestiansky J.
Published: May 2005

The mass spectra of 2,2′‐anhydrouridine, 2,2′‐anhydrothymidine and 2,2′‐anhydro‐4‐thiouridine are reported. The acetyl, trifluoroacetyl, trityl, pivaloyl and trimethylsilyl ether derivatives were also studied. Deuterium labeling in acetyl and trimethylsilyl groups aided characterization of many ions in the spectra, as well as helping to clarify hydrogen migration processes. The anhydronucleosides and their derivatives are readily distinguished from natural nucleosides by the presence of an ion containing the base moiety plus the anhydro‐ring plus one hydrogen atom from the rest of the molecule. As for natural nucleosides the [base + H]+ and [base + 2H]+ ions are usually prominent, but in contrast to natural nucleosides, ions characteristic of the sugar moiety do not retain the 2′‐oxygen atom (i.e. the oxygen atom of the anhydro‐ring). The mass spectra of deuterium labeled derivatives suggest a test for the presence of a 3′‐O‐acetyl function (the O‐acetyl group is lost from the molecular ion much more readily from the 3′‐ than from the 5′‐carbon atom). The trimethylsilyl derivatives showed evidence in their mass spectra for migration of trimethylsilyl groups in addition to hydrogen atoms.
Electron‐impact fragmentations of 1,3‐ and 1,4‐bis‐(cyclopentadienyliron dicarbonyl)tetrafluorobenzenes
Authors: Cohen Stuart C.
Published: May 2005

Although 1,4‐bis(cyclopentadienyliron dicarbonyl)‐tetrafluorobenzene fragments under electron‐impact, losing four CO groups stepwise prior to other observed fragmentations, the corresponding 1,3‐derivative eliminate HF after loss of only two CO groups.
Substituent effects in mass spectrometry: The correlation of the ionisation potentials of substituted benzenes with σp+
Authors: Benoit F.
Published: May 2005

It is demonstrated that the ionisation potentials of mono‐ and di‐substituted benzenes are related to the sum of Brown's σp+ of the substituents for both the meta and para isomers. From this it is concluded that the charge, in substituted arenes, lies predominantly on the aromatic ring rather than on either of the substituents. An empirical equation relating the IP's of mono‐ and disubstituted benzenes to the sum of σp+ is presented.
Appearance potentials as an analytical aid in the evaluation of of non‐bonded interactions. Recalculation of strain energies for some methyl phenanthrenes
Authors: Jalonen Jorma , Pihlaja Kalevi
Published: May 2005

Recently, Dougherty et al.1 reported ionisation potentials for the [M]+· and appearance potentials for the [M  CH3]+ ions of 2,7‐dimethyl‐ (I), 4,5‐dimethyl‐ (II), 2,4,5,7‐tetramethyl‐ (III) and 3,4,5,6‐tetramethyl‐phenanthrenes (IV). For evaluation of strain energies they used the assignments presented by Arnett et al.2 The expression used is shown to be thermodynamically irrelevant and the strain energies of II and IV in comparison to I and III are re‐estimated with the aid of thermodynamically relevant assumptions. A close agreement prevails between the present results and those obtained with comparison of heats of formation.
Transfer processes of alkoxyl groups in iron carbonyl complexes
Authors: Gambino O. , Vaglio G. A. , Cetini G.
Published: May 2005

The mass spectra of Fe2(CO)6C4(COOCH3)4 and Fe2(CO)6C4(COOC2H5)4 are reported. Transfer processes of alkoxyl groups and hydrogen rearrangements are observed, and confirmed by deuterium labelling and the observation of metastable transitions. Fe3(CO)8C4(COOCH3)4 and Fe3(CO)8C4(COOC2H5)4 give similar breakdown patterns. Likely fragmentation schemes are suggested.
Etude de la Fragmentation du Benzisothiazole et de Quelques Benzoselenazoles et Benzisoselenazoles
Authors: Croisy A. , Jacquignon P. , Weber R. , Renson M.
Published: May 2005

Les spectres de masse du benzisothiazole, de trois benzosélénzoles et de trois benzisoséléazoles not été mesurés et comparés à ceux des benzothiazoles correspondants. La perte de CS mise en évidence chez ces derniers est confirmée dans le cas du benzisothiazole, mais un mécanisme différent est proposé.

La fragmentation des analogues séléniés conduit à des ions du même type que dans le cas des benzothiazoles et du benzisothiazole par perte de molécules du type CN—R, cependant, la perte de l'hétéroatome ne s'accompagne pas de perte de carbone. En outre, il semble que la structure isosélénazole soit plus sensible à l'electronolyse que son isomére.

Les six hétérocycles séléniés étudiés ont tous donné naissance à deux ions (130 et 132) provenant d'une recombinaison de divers fragments. Ce phénomène laisse à penser qu'il s'agit là d'un élément caractéristique dans la fragmentation électronique de tels composés.
The electron‐impact induced fragmentation of substituted 4‐styrylquinolines
Authors: Güsten H. , Klasinc L. , Stefanović D.
Published: May 2005

The fragmentation of 4‐styrylquinoline (I), 4‐(p‐nitrostyryl)‐quinoline (II), 4‐(p‐chlorostyryl)‐quinoline (III), 4‐(p‐hydroxystyryl)‐quinoline (IV), 4‐(p‐methoxystyryl)‐quinoline (V), 4‐(p‐dimethylaminostyryl)‐quinoline (VI) and 4‐(p‐cyanostyryl)‐quinoline (VII) under electron‐impact in the mass spectrometer is reported. The role and the influence of substituents on the fragmentation scheme is discussed. The loss of the substituents from the molecular ion is correlated with LCAOMO quantities.
Elektronenstossinduzierte Fragmentierung von Acetylenverbindungen—V: Vergleich der Isomeren Naphthyl‐ und Phenyl‐Pentinen‐Alkohole
Authors: Schwarz Helmut , Bohlmann Ferdinand
Published: May 2005

Die Unterschiede im Fragmentierungsschema der isomeren Naphthyl‐ und Phenylpentinen‐aklohole sind durch Untersuchung der 2H‐ und 13C‐markierten Derivate nachgewiesen worden. Wie durch hochauflösende Massenspektrometrie gezeigt werden kann, wird im Falle der Acetylenverbindung IOn [C9H7]⊕ hauptsächlich durch Keten‐eliminierung aus dem [M – 1]+‐Ion und bei den Naphthalinen durch Abspaltung von Acetylen aus dem Benztropylium‐Ion gebidet. Der vorgeschlagene Mechanismus der CO‐ und CHO‐Abspaltung füBenzylalkohol kann nicht auf die untersuchten Verbindungen übertragen werden.
Fragmentation of reduced dibenzo[b,f][1,4]‐diazocines, ‐oxazocines and ‐thiazocines on electron‐impact
Authors: Millard B. J. , Saunders A. , Sprake J. M.
Published: May 2005

An investigation of the mass spectral behaviour of the title compounds is reported. Two processes have been studied by deuterium labelling. One, which occurs with all three ring systems, results in the loss of a C7H7 radical, whilst the other, which occurs only in the dibenzothiazocine, leads to the loss of a C6H6N radical.
Mass spectra of organoarsenic compounds—I: Electron‐impact‐induced fragmentations of esters of arsenious and thioarsenious acid
Authors: Frøyen Paul , Møller Jørgen
Published: May 2005

The mass spectra of a series of esters of arsenious and thioarsenious acid have been studied, together with that of diethyl methylarsonite. The main fragmentation pathways have been determined with the use of high resolution mass measurements and application of the metastable defocusing technique.

The major fragment ions all contain arsenic and may be ascribed structures implying divalent/trivalent arsenic. Ions implying tetravalent/pentavalent arsenic as well as double hydrogen rearrangement processes are hardly recognisable; this is in contrast to the findings reported for the corresponding phosphorous compounds, with which a comparison is made.

The present results are in accordance with the view that arsenic is less capable than phosphorous of achieving multiple bonding to other atoms by means of its empty d orbitals.
Quantitative mass spectrometry by internal standardisation using a single focusing mass spectrometer and the peak switching facilities of a peak matching device
Authors: Seiler N. , Knödgen B.
Published: May 2005

A quantitative mass spectrometric method for the determination of small sample sizes is described. This method is applicable to both single and double focusing mass spectrometers, if a conventional peak matching device or any other suitable peak switching facility is attached to the instrument.

In the conventional integrated ion current technique a constant pressure of the vapour of hepta‐cosafluoro‐tri‐n‐butylamine or a comparable standard is maintained in the analyser. By contrast to this in our method the calibrating substance is evaporated together with the sample from the same capillary of the probe. Substances with a similar chemical structure (in most cases higher or lower homologues) can be used as internal standards. Since thermal effects in the probe and sensitivity changes of the mass spectrometer during the flash evaporation of the substances affect the integrated ion current curves of both sample and standard equally, the ratio of the curves is largely independent of these parameters.

With a single focusing mass spectrometer (CH‐5 Varian, MAT) reproducibilities of the determinations were within ±10%, with substance amounts in the range between 10−10 to 10−11 mole.
Mass spectrometric identification of oleanolic and ursolic acids
Authors: Grilanc P. , Milivojević D.
Published: May 2005

p‐Toluidides of 3‐acetoxy ursolic and 3‐acetoxy oleanolic acids were prepared. On the basis of different intensities of the m/e 452 and 453 peaks the identification of oleanolic and ursolic acids is possible.
Isotope effects upon hydrogen atom loss from molecular ions
Authors: Bertrand M. , Beynon J. H. , Cooks R. G.
Published: May 2005

The isotope effect (TH/TD) upon the kinetic energy release and the isotope effect (kH/kD) upon ion abundance for unimolecular H· loss from molecular ions has been determined for several compounds. It is suggested that the isotope effect upon abundance might provide a convenient method of estimating the relative life‐time of ions which fragment in the metastable region for different instruments or different experimental conditions. The value of kH/kD varies from <2 to >1000 for different molecular ions and this variation is apparently largely due to the rate of increase of the reaction rate with internal energy in the threshold region. The magnitude of the isotope effect is thus related to the entropy of activation. The isotope effect upon energy release was found to be slightly less than unity in almost every case studied; this included both reactions in which the reverse activation energy is very small and those in which it is appreciable.
The mass spectra of some selenoureas and selenothiocarbamic esters
Authors: Kirkien Alicja M. , Shine Robert J. , Plimmer Jack R.
Published: May 2005

The mass spectra of five selenoureas and two selenothiocarbamic esters are reported and discussed. Fragmentation modes are compared with those reported for the ureas, thioureas, carbamates and thiocarbamates.
Computer programmes for representing mass spectra on a computer plotter
Authors: Tashma Zeev
Published: May 2005

The Fortran IV programmes have been written for plotting mass spectra on a Calcomp 565 plotter. The spectra can be displayed sequentially or one on top of the other. One of the programmes also calculates relative abundance and percent sigma for each peak, and possible origins for metastable peaks.
Some aspect of the doubly‐charged ion chemistry of armoatic amines and diamines
Authors: Ast T. , Beynon J. H.
Published: May 2005

Doubly‐charged ion mass spectra of aromatic amines and diamines, as opposed to those of the aromatic hydrocarbons, show strong correlation with empirical formula.[M]++is usually the base peak in the spectrum and its main fragmentation involves loss of C2H2, in sharp contrast wit the [M]+˙ ion which always loses HCN. Measurement of the Kinetic energy released in chargeseparation reactions can yield useful structural information. Result strongly support the concept of charge‐localization on nitrogen atoms. Extensive scrambiling prior to nfragmentatiom was observed in all isomeric compoounds studied.
A new ion reaction pathway of 1,2,4‐thiadiazole
Authors: Shoeb A. , Popli S. P. , Gopalchari R.
Published: May 2005

The fragmentation pattern of 3‐amino‐1,2,4‐oxadiazole involving a new type of hydrogen migration reaction has been discussed.
The mass spectrum and fragmentation mechanism of exo‐ and endo‐ norborneol
Authors: Holmes J. L. , McGillivray D.
Published: May 2005

The mass spectra of exo ‐and endo‐norborneol and a number of deuterium labelled and‐logues have been studied in detail. The two alcohols have common fragentation pathways, the major routes of which can be related to specific rearrangements of the molecular ion. The loss of water from the molecular ion consists of two processes, one involving and one4 not involving the hydroxyl hydrogen atom. The limitions of the labelloing experiements are discussed.
The fragmentation of some alkyl thio‐phosphate esters by electron‐impact
Authors: Santoro E.
Published: May 2005

The mass spectra of the following compounds have been studied:

equation image

and the fragmentation pathways established with the aid of accurate mass measurements, metastable transition and appearance potential determination. The mass spectra show that the sulphur‐containing compounds (II to IV) give a stronger molecular ion that that of compound I. A further significant difference is the low intensity, in the mass spectra of II to IV, of the fragments relative to the processes that occur in I, probably because the electron removed upon ionisation belongs to the sulpher atom in compounds II to IV and to the oxygen in compound I. The isomeric compounds, (III and IV) show quite different mass spectra, The radicals containing only Phosphorus and oxygen have an ionisation potential close to 9 eV and the presence of sulphur considerably lowes this value. The measured ionisation potentials of compounds I to IV are respectively, 10·70, 9·55, 9·20 and 9·00eV. The heats of formation of compounds II and III have been estimated as −176 and −118 Kcal mole−1, respectively.
Towards A qualitative rationalisation of the fragmentation reactions of organic negative molecular ions
Authors: Alexander R. G. , Bigley D. B. , Todd J. F. J.
Published: May 2005

A set of axioms is formulated which provides a means for the qualitative rationalization and prediction of the fragmentation modes of organic molecular anions.
Substituent effects on rearrangements in aromatic aldoximes
Authors: Das K. G. , Kulkarni P. S.
Published: May 2005

The effect of substituents on hydrogen and hydroxyl transfer in substituted benzaldoximes reveals interesting differences. A possible explanation in terms of radical electron site and charge site is suggested.
The mass spectra of the pyrethrins and related compounds
Authors: Pattenden G. , Crombie L. , Hemesley P.
Published: May 2005

The mass spectra of the natural pyrethrins, allethrin, the chrysanthemic acid, and the rethrolonyl and rethronyl portions of the insecticidal esters are presented, and their main fragmentation pathways are discussed.
Variantes de mycosides caracterisees par des residus glycosidiques substitues par des chaines acyles–I: Spectres de masse des mycosides G′ et A′ peracetyles
Authors: Gastambide‐Odier Mireille
Published: May 2005

Les spectres de masse des mycosides G′ et A′ peracétylés sont caractérisés par des ions oxoniums réarrangés correspondant à des désoxysucres substitués qui auraient perdu une chaǐne acyle par fragmentation dans le spectrographe de masse.

Le constituant glycosidique majeur du mycoside G′ est un désoxysucre avec une chaǐne acyle et un groupement méthyle. Le mycoside A′ contient des désoxysucre avec une chaǐne acyle et 0, 1 ou 2 méthyles. I1 existe ausi des désoxysucres sans chaǐne acyle mais avec un (G′, A′) ou deux (A′) méthyles.

Les spectres de masse indiquent que les chaǐnes acyles pourraient ětre du type mycolique: I1 existe des pics qui pourraient correspondre à une coupure des deux cǒtés de la ramification méthyle magnified image et le fragment CH+˙CC22H45, trouvé dans le spectre du mycoside G′ paracétylé, est caractéristique de la chaǐne raifiée. Les pics les plus élevés (m/e 1072 et 1100) du spectre du mycoside A′ paracétylé correspondraient à une chaǐne mycolique, après l'élimination d'une molécule d'acide acétique, d'une molécule de méthanol et perte d'un H (l) ou l'élimination d'une molécule d'acide acétique et perte d'un H (m).

Les měmes spectres permettent de preéciser la nature et l'abondance des acides mycocérosiques qui estérifent les aglycones et confirment aussi la structure de ces aglycones qui a été établie antérieurément par dégradation et par spectrométric de masse. La mycoside G′ est caractérisé par des acides mycocérosiques en C27 et C24 et le mycoside A′ par des acides mycocérosiques en C29, C32, C30 et C27 qui sont classés par ordre d'importance décroissante.
High resolution field desorption mass spectrometry—I: Nucleosides and nucleotides
Authors: Schulten H. R. , Beckey H. D.
Published: May 2005

The first complete high resolution (HR) field desorption (FD) mass spectra (MS) are presented and constitute a helpful tool in the structure elucidation of biologically significant compounds. This is especially relevant for the determination of the molecular weight of substances with very low volatilities which suffer from thermal decomposition when evaporated into the ion source. An additional advantage is the very small sample consumption (in the submicrogram range).

Further improvements in the ion production method are the introduction of high temperature activated emitters and a specially designed micromanipulator for optimal adjustment of the field anodes. These enabled values of mass resolution between 15000 and 25000 (10% valley definition) to be achieved when vacuum evaporated Ag Br plates were used for photographic recording.
Massenspektrometrische Untersuchung aromatischer Halogenide der Summenformel C9H11Cl: Mechanismus der Äthylen‐Abspaltung aus dem Ion [M  Cl]+˙
Authors: Köppel Claus , Schwarz Helmut , Bohlmann Ferdinand
Published: May 2005

Durch die Untersuchung 2H‐ und 13C‐markierter isomerer C9H11Cl‐Verbindungen wird gezeigt, dass das [M  C]+‐Ion bevozugt über alkylsubstituierte Tropylium‐Ionen unter C2H4‐Abspaltung in das Ion [C7H7]+ übergeht. Phenylierte Cyclopropan‐Kationen haben, wenn überhaupt, nur einen geringen Anteil an diesem Fragmentierungsvorgang.
Intramolecular transfer reactions induced by electron‐impact. Transsulfonations and transmethylations in polymethylene glycol dimethanesulfonates
Authors: Pomonis J. George , Nelson D. R.
Published: May 2005

The dimethanesulfonate esters of polymethylene glycols undergo three types of double‐group transfer reactions as a result of electron‐impact mass spectrometry: 1. Transfer of a hydrogen and one methanesulfonate group to the second methanesulfonate with cleavage to yield a protonated methanesulfonic acid anhydride. 2. Transfer of two hydrogens to a methanesulfonate group with cleavage to yield a protonated methanesulfonic acid. 3. Transfer of a hydrogen and a methyl group to the second methanesulfonate with cleavage to yield a protonated methyl methanesulfonate. Bicyclic transition states are proposed for these reactions.
Mass spectra of vinyltrimethylsilane and vinyltri(methyl‐d3) silane
Authors: Smolinsky G. , Vasile M. J.
Published: May 2005

This paper reports the mass spectrum of vinyltrimethylsilane over the range of electron‐impact energy of 9 to 70 eV as determined with a quadrupole mass spectrometer. Less extensive data obtained with magnetic spectrometers are included for comparison as well as the spectrum of vinyl‐tri(methyl‐d3)silane. Plots of ion intensity as a function of electron energy, nominal appearance potentials and metastable ion transitions are given.

The primary ionization results in an electron deficiency on the silicon atom, followed by loss of either ·CH3, C2H4 or ·C2H3 to give fragments of mass 85, 73 or 72, respectively. The primary fragment of mass 85 loses C2H2 to give the mass 59 ion. The primary fragment of mass 73 loses successively C2H4 and H2 to give first the mass 45 ion and then the mass 43 ion. At 15 eV, the relative intensities of the ions are 85 > 72 > 100 > 59 > 73. At 70 eV, the relative intensities are 59 > 85 > 43 > 45 > 73 > 72 > 100.
Mass spectrometry of organic compounds in the group V elements–III: Amides, acylphosphines and vinylogues
Authors: Kostyanovsky R. G. , Plekhanov V. G. , Khafizov Kh. , Zagurskaya L. M. , Kadorkina G. K. , Elnatanov Yu. I.
Published: May 2005

Distinct differences are observed on comparison of the fragmentation of tertiary amides (I to XI), and acylphosphines (XII to XVII) and (XX to XXII) under electron‐impact, as well as of their vinylogues (XXIII to XXXI) and (XXXIV to XXXV).
Specific and stereospecific water eliminations in the mass spectra of bicyclo[3.3.1]nonanols
Authors: Cable J. , MacLeod J. K. , Vegar M. R. , Wells R. J.
Published: May 2005

By the use of site‐specific and stereospecific deuterium labelling, it has been possible to show that loss of the elements of water from all possible bicyclo[3.3.1]nonanols (I to V) in the mass spectrometer, takes place in a substantially stereospecific manner. The position of abstraction of the hydrogen atom by the hydroxyl group can be related to the proximity effects that are present in the ground state conformers, while the [M]+ / [M – H2O]+ ratio appears to depend on the minimum H–‐OH intramolecular distance in the more stable conformations.
Sur la Fragmentation d'Isosteres Phenanthreniques Soufres et Selenies
Authors: Jacquignon P. , Croisy A. , Renson M. , Iteke E. , Christiaens L.
Published: May 2005

Dans le présent travail nous avons étudié six composés isostères du phénanthrène contenant simultanément un atome de soufre et un atome de sélénium ou deux atomes de sélénium.

La configuration de ces molécules influence la fragilité des liaisons CSe, laquelle semble liée au degré d'aromaticité du noyau auquel l'hétéroatome de sélénium est fixé.

Si l'allure générale des spectres est assez voisine de celle des spectres des analogues sulfurés, du benzothiophène, il n'en reste pas moins, comme c'est le cas pour tous les hétérocycles séléniés étudiés jusqu'à présent que la dégradation essentielle de tels composés est la perte du sélénium hétéroatomique, sans que le cycles adjacents soient affectés par cette fragmentation.
Negative ion mass spectra of dicarboxylic acids
Authors: Ito Akihiko , Matsumoto Kozo , Takeuchi Tsugio
Published: May 2005

The negative ion mass spectra of dicarboxylic acids show [M]−˙ and prominent [M – H]−ions. These ions can therefore be used to determine the molecular weight of dicarboxylic acids which do not give positive molecular ions. The [C2H3]− ion is a base peak in the spectra of maleic and fumaric acids. Isomeric phthalic acids are readily differentiated.
Etude Quantitative de la Reactivite–XXI: Comportement sous l'Impact Electronique de Bromures de Cyclopentyle et Cyclohexyle α‐substitutes cis et trans
Authors: Gounelle Yves , Péchiné Jean‐Marie , Solgadi Daniel
Published: May 2005

Les spectres de dix couples de bromures de cyclopentyle et de cyclohexyle α‐substitués cis et trans sont enregistrés pour onze énergies d'ionisation distinctes comprises entre 10 et 20 eV. Pour chaque isomère un calcul du spectre de masse et de ses variations avec l'accélération électronique basé sur la théorie du quasi‐équilibre nous a permis une estimation des énergies d'activation dela rupture principale [M – Br]. Ces évaluations montrent que les différences observées entre les spectres de masse de diastéréoisomères dépendent essentiellement soit de la différence d'enthalpie entre les ions isomères àl'état fondamental lorsque le substituant est un fluor ou un oxygène, soit de la différence d'enthalpie entre les états de transition isomères de la rupture [M – Br] lorsque le substituant est un chlore ou un brome; ce qui dans ces derniers cas s'interprète par l'intervention d'une participation de l'halogène au départ du brome pour les isomères trans.
Stereospecific hydrogen migration in retro‐diels‐alder fragmentation of some polycyclic imides
Authors: Lesman Thila , Deutsch Joseph
Published: May 2005

A stereospecific ‘retro‐Diels‐Alder’ fragmentation followed by hydrogen migration was found in the mass spectra of imides and phenyl imides of decahydroindacene 4,5‐dicarboxylic acid. The fragmentation involves a one hydrogen atom rearrangement when the charge is retained on the diene moiety and double hydrogen rearrangement when the charge is on the dienophilic moiety.
Mass spectra of some syn‐ and anti‐aromatic aldoximes
Authors: Brown Ellis V. , Hough Lindsay B. , Plasz Andrew C.
Published: May 2005

The mass spectra of eight pairs of geometric isomers of aromatic oximes and four other single aromatic oximes are reported. The loss of H2O, HO and HCN are major fragmentations from the molecular ion of all the benzaldoximes studies; however, the loss of HCN from the molecular ion did not occur in the oximes of 9‐phenanthraldehyde, 1‐naphthaldehyde and 2‐naphthaldehyde. The halogen substituted benzaldoximes eliminate HCNO and H2CNO forming an additional fragmentation pathway from the molecular ion. In general, variations were found for each pair of syn‐ and anti‐oximes but no consistent patterns could be found in the spectra for all the syn‐isomers versus all of the anti‐isomers. The geometric isomerism of four oximes previously reported in the literature have been established for the first time as anti‐m‐bromobenzaldoxime, syn‐9‐phenanthraldoxime, syn‐1‐naphthaldoxime and syn‐2‐naphthaldoxime. Three new oxime acetates were prepared and their mass spectra are discussed.
Mechanism of enolic ion tautomerization
Authors: Eadon George
Published: May 2005

Evidence of enolic ion‐enolic ion tautomerization was observed in the mass spectra of several alkylcyclobutanols and aliphatic ketones. Extensive deuterium labeling experiments on 1‐butylcyclobutanol, 5‐nonanone and 7‐tridecanone demonstrated that the process did not involve the intermediacy of the ketonic ion. The predominant mechanism involves reciprocal hydrogen transfers through large ring transition states, rather than a direct 1,3 hydrogen shift. Other decomposition reactions of the enolic ions were observed.
Continuous wave laser induced degradation of polystyrene monitored by time‐of‐flight mass spectrometry
Authors: Coloff Stanley G. , Vanderborgh Nicholas E.
Published: May 2005

The laser induced degradation of polystyrene within the ion‐source housing of a time‐of‐flight mass spectrometer is described. A low power, CO2 laser was used to produce a steady state flux of degradation products. This method permits the use of normal recording techniques. The degradation of polystyrene is reported using this technique. Evidence is presented that the monomer is ejected from the irradiated surface. Degradation in the presence of oxygen and nitrogen is also described. Oxygen promotes the fragmentation of styrene while nitrogen shows the opposite effect.
The mass spectra of some pentafluorophenylthio derivatives
Authors: Jamieson W. D. , Peach M. E.
Published: May 2005

Ionic fragmentations induced by electron‐impact on compounds of the type C6F5SX (X  H, CH3, COCH3, Cl, C6F5) and (C6F5S)2, (C6F5S)2Hg, (C6F5S)3As and (C6F5SCH2)2 have been studied. Principal features of the mass spectra are reported. The [C6F5S]+ ion (m/e 199) is predominant and its mode of fragmentation has been deduced. The precursor ions for m/e 199 have been examined in (C6F5)2S, (C6F5S)2, (C6F5S)2Hg, (C6F5S)3As and C6F5SCl. Ion kinetic energy spectra of (C6F5)2S, (C6F5S)2, (C6F5S)2Hg and C6F5SCl have been recorded, and all contain peaks corresponding to the fragmentation of the [C6F5S]+ ion.
1,1‐Elimination of HCN from propionitrile under electron‐impact. Hydrogen migration in the molecular ion
Authors: Meyerson Seymour , Karabatsos G. J.
Published: May 2005

The dominant primary reactions of propionitrile under electron‐impact effect loss of HCN and loss of H·. Deuterium labeling shows that the hydrogen atom lost as HCN comes chiefly from C‐2, but that lost as a free atom comes chiefly from C‐3. Both reactions are probably preceded by a 1,2 hydrogen migration to yield an allylic‐like molecular ion, \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm CH}_{\rm 3}{\rm C}^+ {\rm HCH = N}^{\rm .} \leftrightarrow {\rm CH}_{\rm 3} \mathop {\rm C}\limits^{\rm .} {\rm HCH = N}} \right]^+ $\end{document}.
Organische Schwefelverbindungen—IV: Elektronenstossinduzierte Redoxreaktion von ortho‐Nitrothiobenzoesäure‐S‐p‐tolylester
Authors: Martens Jürgen , Praefcke Klaus , Schwarz Helmut
Published: May 2005

Die elektronenstossinduzierte Fragmentierung der nitrothiobenzoesäure‐S‐p‐tolylester führt bei der ortho‐Verbindung zu einer bisher unbekannten Umlagerung, bei der in Form einer intramolekularen Redoxreaktion ein Sauerstoff der Nitrogruppe zum Schwefel der Thiolester‐Gruppierung wandert. Die Stellung der Nitrogruppe beeinflusst nicht nur wesentlich das Fragmentierungsbild, sondern darüberhinaus in dramatischer Weise die Lebensdauer des Molekül‐Ions.
Mass spectra of monosubstituted trans‐stilbenes
Authors: Güsten H. , Klasinc L. , Kramer V. , Marsel J.
Published: May 2005

The mass spectra of twenty‐eight monosubstituted trans‐stilbenes in ortho, meta, para and alpha positions with N(CH3)2, NH2, OCH3, OH, Br, Cl, F, CH3, COOH, CN and NO2 groups as substituents have been studied. A detailed fragmentation pathway is given for stilbene. This fragmentation, characteristic for most of the substituted stilbenes, takes place either from the molecular or from the [M ‐ Substituent] ion. In o‐nitro‐, o‐methoxy‐,α‐carboxyl‐ and α‐methylstilbene, however, rearrangement reactions prior to fragmentation influence the fragmentation pattern.
The electronic structure of ionised molecules—VIII: Ethylamine
Authors: Krier C. , Lorquet J. C. , Berlingin A.
Published: May 2005

Wavefunctions for the [C2H5NH2]+˙ ion in its electronic ground state have been calculated by two variants of the CNDO method. The potential energy surface, the reaction paths, the charge distribution and the overlap populations have been calculated as functions of the internuclear distances in order to elucidate the fragmentation mechanism. The results are compared with the description given by other methods in current use, namely the mechanistic approach and the Hirofa method. The reliability and limitations of the three methods are discussed.
The mass spectra of some methyl alkanesulphinates
Authors: Filby W. G. , Penzhorn R.‐D. , Stieglitz L.
Published: May 2005

Mass Spectra of the methyl esters of ethane, n‐propane, isopropane, n‐butane, sec‐butane and tert‐butane sulphinic acids have been determined. In general, the parent ions are of low abundance and the most prevalent are the hydrocarbon ions which arise by α‐cleavage. Other ions that serve to characterise these compounds are those from the CH4SO2 and HSO2 fragments.