bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elctron‐impact studies of diazadiphosphetidines
Authors: Schlak O. , Schmutzler R. , Gregor I. K. 
Published: May 2005

AbstractElectron‐impact studies of diazadiphosphetidines,[YF2PNMe]2(YF,Me, Ph, MeO,2,5‐Me2C6H3, and m‐CF3C6H4) are reported, the most abundant fragments corresponding to m/e [M/2–1]+, [M/2]+ and [M/2–1]+. It is concluded from metastable data that formation of the noval rearrangement ion, [M]+→[M/2+1]+is predominantly due to an electron‐impact process. Variable temperature spectra of(F3PNMe)2, (i.e. for Y=F), suggest that ions of m/e [M/2‐1]+are formed, in part, by a thermal process. For the compound [(m‐CF3C6H4)F2PNMe]2 a well resolved negative ion spectrum has been obtained, with the molecular ion present in 100% abundance.
Fragmentation des Closo‐N‐Methyl Phosphorimide, Thiophosphorimides et Arsenimide
Authors: Wolff Anne , Cambon Aimé , Riess Jean 
Published: May 2005

AbstractLes spectres de masse du closo phosphorimide P4(NCH3)6Sn, où n = 1 à 4, et du closo arsenimide As4(NCH3)6 ont été et des schémas de fragmentations systématiques ont été dégagés, L'introduction des groupes thiophosphoryles se traduit par une superposition des deux types de fragmentations identifiées pour P4(NCH3)6 P4− dérivés ou de l'hexaméthylène tétramine.
Organische Schwefelverbindungen. IX—Ringkontraktion Statt Carben‐Eliminierung von Neutralteilen Bei der Elektronenstossinduzierten Fragmentierung von Thiaspirofuranonen
Authors: Schwarz Helmut , Praefcke Klaus , Höhne Gerhard 
Published: May 2005

AbstractBei der elektronenstoßinduzierten Fragmentierung des Thia‐spirofuranons findet ein Prozeß statt, der am besten durch die Annahme einer Ringkontraktion des Neutralteiles C6H10 rationalisierbar ist. Eine Carben‐Struktur für dieses Neutralteil kann ausgeschlossen werden.
Electron‐impact fragmentation of triaryl‐s‐trithianes: A novel skeletal rearrangement involving sulphur‐sulphur bond formation
Authors: Chattopadhyaya Jyoti B. , Rao A. V. Rama 
Published: May 2005

AbstractThe mass spectral fragmentation of seven substituted 2,4,6‐triaryl‐s‐trithianes has been studied and the fragmentation modes confirmed by deuterium labelling. Triphenyl‐s‐trithiane shows some interesting features in its mode of cleavage and does not eliminate S, S2, SH˙, H2S or S2H˙ from its molecular ion. The prominent radical ions in the mass spectrum are at m/e 180 (52.3%) and m/e 186 (45.2%), corresponding to stilbene and PhCHS3. Their compositions have been established by deuterium labelling and accurate mass measurements. The formation of stilbene indicates a relationship between pyrolytic and electron‐impact studies. The origin of [PhCHS3]+˙ suggests that one of the sulphur atoms attaches itself to the other two sulphur atoms in the molecular ion, eliminating a stilbene radical ion. The other important fragmentation corresponds to the monomer radical ion (thiobenzaldehyde) and the thiobenzoyl cation.Among the other substituted triaryl‐s‐trithianes with substituents such as chloro, methoxy, methylenedioxy and hydroxy groups on the phenyl ring (IV to IX), only the tris‐(p‐chlorophenyl)‐s trithiane shows an insignificant molecular ion. Unlike the triphenyl derivative, the chloro, methoxy and methylenedioxy derivatives show the loss of HS˙ and/or H2S from the molecular ion. The spectrum of tris‐(p‐hydroxyphenyl)‐s‐trithiane corresponds to the spectrum of p‐hydroxythiobenzaldehyde.
Elektronenstossinduzierte Arylwanderungen bei 2.2‐Disubstituierten 1.3‐Dioxolen
Authors: Schwarz Helmut , Schönberg Alexander , Singer Erich , Schulze‐Pannier Heidemarie 
Published: May 2005

AbstractBei der elektronenstroßinduzierten Fragmentierung 1.3‐Dioxolen werden im Gegensatz zu sonstigen Arylwanderungen sowohl die nucleophile als auch die elektrophile Gruppe umgelagert. Anßerdem wird in einem Fall eine ungewöhnlich intensive Spaltung geminaler Bindungen am Spiro‐Kohlenstoff beobachtet, die durch die Produkt‐Stabilität des doppelt geladenen Fragment‐Ions erklärbar ist.
Probability based matching of mass spectra. Rapid identification of specific compounds in mixtures
Authors: McLafferty F. W. , Hertel R. H. , Villwock R. D. 
Published: May 2005

AbstractAn automated system is described for computer examination of the mass spectrum of an unknown mixture for the presence of a specific compound. The probability that the compound is present is indicated as a ‘confidence index’ K; 2K should signify the average number of compounds, selected at random, whose mass spectra would have to be examined to find data which match the target spectrum to the same degree as does the unknown. The value of K is determined by the uniqueness U of the m/e value, the abundance A, and the criterion of abundance agreement W of the matching peaks, and of the compound concentration D in the sample. Application to spectra from a variety of compounds, including illicit drugs, indicates that the system has high sensitivity and selectivity, and that the value of K is a useful index of the reliability of the identification. Initial testing of this system has utilized an automated quadrupole mass spectrometer under control of a dedicated microcomputer with sample introduction through a flash evaporator and membrane separator.
Massenspektrometrische Untersuchung von Bromiden: Über den Einfluss der Radikalstabilität auf die Ringgrösse Cyclischer Bromonium‐Ionen
Authors: Schwarz Helmut , Bohlmann Ferdinand , Hillenbrand Günther , Altnau Gerald 
Published: May 2005

AbstractDie Existenz von füntf‐ oder sechsgliedrigen cyclischen Bromonium‐Ionen, die aus ω‐Phenyl‐alkylbromiden unter Elektronenstoßbendingungen erzeugt werden, hängt in entscheidender Weise von der Stabilität der Phenyl‐Alkyl‐Radikale ab.
Studies in organic mass spectrometry. XVIII—The effect of branching in the sidechain upon the fragmentation of 4,6‐dialkyl‐1,3‐dioxanes
Authors: Monstrey J. , van de Sande C. , Vandewalle M. 
Published: May 2005

AbstractThe presence of a 2′‐tertiary hydrogen atom has a profound influence on the general fragmentation pattern of 4,6‐dialkyl‐1,3‐dioxanes. Branching at the 2′‐position induces a double hydrogen transfer reaction which is absent in the spectra of 4,6‐n‐alkyl‐1,3‐dioxanes.
o‐nitroaniline derivatives. IV—The mass spectra of o‐nitroanils
Authors: Johnston David , Smith David M. 
Published: May 2005

AbstractThe principal feature of the mass spectra of o‐nitroanils, ArCHNC6H4NO2(o‐), is an intense peak corresponding to the [ArCO]+ ion; this implies oxygen transfer from the nitro group to the azomethine carbon during the fragmentation process. In this series of anils, loss of OH from the molecular ion is not apparently an important fragmentation pathway, in contrast to the fragmentation of o‐nitrobenzylideneanilines. Benzylideneaniline derivatives with an o‐nitro substituent in both rings have mass spectra which indicate interaction of both nitro groups with the CHN group, but in this series of spectra the [M—17]+ ion is again of low intensity.
Sauerstoffwanderung vom Phosphor zum Kohlenstoff Beim Massenspektrometrischen Zerfall von α,α‐ Dichloralkylphosphonsäurechloriden
Authors: Schmidtberg G. , Hägele G. , Bauer G. 
Published: May 2005

AbstractDurch Chlor‐Sauerstoff‐Austauschreaktionen entstehen beim massenspektrometrischen Zerfall von α,α‐Dichloralkylphosphonsäure‐ und ‐phosphinsäurechloriden Carbonyl‐fragmente. Im Spektrum von α.β‐Dichlorvinylphosphonsäuredichlorid bildet Chlorketen CHClCO sogar den Basispeak.
Effects of halogen atoms on the mass spectra of some 3‐phenylpropionyl halides
Authors: Hittenhausen‐Gelderblom R. , Venema A. , Nibbering N. M. M. 
Published: May 2005

AbstractThe mass spectra of the title compounds have been studied by use of deuterium labelling. The character of the halogen atom appears to have a marked influence on the fragmentation pathways. It is shown that the acyl halide group may react with the different active atoms in the molecular ion—the α‐ and β‐hydrogen atoms—as well as with the phenyl ring.
Massenspektrometrische Untersuchungen an Benzophenon und Substituierten Benzophenonen. I‐Ermittlung Thermodynamischer Grössen
Authors: Krenmayr P. , Heller R. , Varmuza K. 
Published: May 2005

AbstractEs wurden die Ionisieerungspotentiate von Benzophenon und substituierten Benzophenonen sowie die Auftrittspotentiale der häufigsten Fragment‐Ionen gemessen. Ausgehend von berechneten Werten für die Bildungsenthalpien der substituierten Benzophenone, wurden folgende Grüßen ermittelt: Bildungsenthalpien der Molekül‐Ionen; Bildungsenthalpien von Fragment‐Ionen, die in einem einstufigen, und solcher, die in einem zweistufigen Zerfallsprozeß gebildet wurden; Bildungsenthalpien und Ionisierungspotentiale von Radikalen; Dissoziationsenergien des Benzophenons und der substituierten Benzophenone. Die Genauigkeit der Ergebnisse wird diskutiert.
Mass spectrometry of heterocyclic compounds. VI—retro‐1,3‐dipolar cycloaddition and competitive fragmentation reaction of 2,5‐diaryl‐1,3,4‐dioxazoles
Authors: Selva A. , Citterio A. , Pella E. , Tonani R. 
Published: May 2005

AbstractThe process of retro‐1,3‐dipolar cycloaddition of 2,5‐diaryl‐1,3,4‐dioxazoles induced by electron‐impact is discussed. For this purpose, 2‐phenyl‐5‐p‐chlorophenyl‐1,3,4‐dioxazole was prepared, labelled with 18O in position 1; the spectrum of this compound showed clear evidence of retro‐cycloaddition, the dipole fragment retaining the positive charge. This labelled compound also provides a reliable interpretation of other cleavage modes of the heterocyclic ring. The elemental compositions of the ions considered were determined by exact mass measurements and the metastable transitions were detected through the defocusing technique of the electrostatic sector.
Electron‐impact spectra of 2‐acyloxyacetophenones
Authors: Stockburn A. L. , Thomas C. W. 
Published: May 2005

AbstractThe mass spectra of a number of 2‐acyloxyacetophenones (phenacyl esters) are reported. The major fragments in the spectra are due to α‐fission to oxonium ions. A correlation between the intensities of the oxonium ions and Hammett substituent constants is noted. Rearrangements are examined by means of deuterium labelling and low electron voltage studies.
Collisional activation spectra of the [C9H11O]+ ion from 2‐methyl‐2‐phenylpropane‐1,3‐diol
Authors: Nibbering N. M. M. , Van De Sande C. C. , Nishishita T. , McLafferty F. W. 
Published: May 2005

AbstractCollisional activation spectra show that the [C9H11O] ion formed by loss of CH2OH from the title compound has rearranged to the protonated phenylacetone structure.
Mechanismus der Amin‐eliminierungen bei der Elektronenstoßinduzierten Fragmentierung von 1.3‐Diaminopropanen
Authors: Eckhardt G. , Goebel K. J. , Tondorf G. , Goenechea S. 
Published: May 2005

Abstract1,3‐Diaminopropane spalten beim Elektronestoßinduzierten Zerfall in starkem Maße aus den Molekülionen Amine ab. Dem schließen sich Folgereaktionen an, in deren Verlauf Vorzugsweise ein Substituent vom C‐2 der Propankette, in geringerem Maße jedoch auch ein N‐Substituent eliminiert werden. Erniedrigung der Elektronendichte an nur einem Stickstoffaton durch geeignete Substituenten führt Zu einem Intensitätsabfall beider [M–Amin]+˙ Ionen. Die zugrun‐deliegenden Fragmentierungsprozesse wurden mit Hilfe deuterierter Verbindungen untersucht.
Chlorine atom migration in the fragmentation of α‐mesyl sulfonyl chlorides
Authors: Hardstaff W. R. , Langler R. F. , Newman M. J. 
Published: May 2005

AbstractThe mass spectra of alkanesulfonyl chlorides can be rationalized by loss of a chlorine atom from the molecular ion, followed by loss of SO2 with concomitant alkyl cation formation. The mass spectra of two α‐mesyl sulfonyl chlorides exhibit a new fragmentation process in which the chlorine atom initially attached to sulfur migrates to the α‐carbon atom with loss of SO2, thereby resulting in retention of chlorine in the alkyl cation.
Ortho effects in organic molecules on electron‐impact I—Oxidation of olefinic double bond by the ortho nitro group in stilbazoles
Authors: Ramana D. V. , Vairamani M. 
Published: May 2005

AbstractThe electron‐impact‐induced fragmentation in 2′‐nitro‐4‐stilbazole is triggered by the oxidation of the olefinic double bond by the ortho nitro group in the initial step, while such an interaction under the same condition is totally absent in the meta and para isomers. The important fragmentation in 2′‐nitro‐2‐stilbazole is the formation of a cyclised ion with the elimination of the nitro group.
Mass spectrometry of heterocyclic compounds. VII—Evidence for common structure(s) of 1,2‐benzisothiazole and benzothiazole molecular ions produced by electron‐impact
Authors: Selva Antonio , Vettori Umberto , Gaetani Enrico 
Published: May 2005

Abstract1,2‐Benzisothiazole and benzothiazole ion kinetic energy spectra, and metastable ion relative abundances of the same primary and secondary decomposition processes are compared. The results are interpretable as postulating slow (metastable) process(es) involving common structures and fast process(es)which are structurally dependent. Analogous indications are given by the interring H/D scrambling data, preceding the loss of DCN (or HCN) from 1,2‐benzisothiazole‐3‐d1 and benzothiazole‐2‐d1 molecular ions, measured in either metastable or normal daughter ions at various electron beam energies.
Studies in organic mass spectrometry. XX—Stereospecificity in hydrogen transfer reactions in mass spectra of TMS derivatives of some 2,3‐dialkyl‐1, 4‐cyclopentanediols
Authors: Maenhaut‐Claeys M. , De Clercq P. , Vandewalle M. 
Published: May 2005

AbstractThe mass spectra of TMS ethers of 2,3,‐dialkyl‐1,4‐cyclopentanediols having a 2′‐carboxyl group or 2′‐double bond in one of the sidechains, display a stereospecific rearrangement process. A mechanism is proposed to account for this stereospecificity.
Mass spectral correlations of halogenated 1,1,1,3,3,3‐hexafluoropropanes and 1,1,1‐trifluoroethanes
Authors: Naae Douglas G. , Wiebe Donald A. 
Published: May 2005

AbstractThe mass spectral fragmentation patterns at 20 eV of twelve compounds of the type CF3CXYCF3 (X, Y =F, Cl, Br, I, H) and five compounds of the type CF3 CX2 Y (X, Y= F, Cl, Br) were analyzed. It was noted that the frequency of carbon–helogen and carbon–carbon bond cleavage was quite dependent on the substituents X and Y.
Ortho effects in organic molecules on electron‐impact II– Ortho effects in substituted α,α,α‐trichloracetanilides
Authors: Ramana D. V. , Vairamani M. , Kala S. 
Published: May 2005

AbstractElimination of trichloromethyl radical from the molecular ion is the abundant fragment in the mass spectra of most of the thirteen substituted trichloracetanilides studied. Unusual ortho effects of OCH3, NO2 and COOH groups are noticed only after the initial ejection of trichloromethyl radical from the molecular ion.
The behaviour of arylsulfonylmethyl sulfonates under conditions of electron‐impact. The loss of CH2O
Authors: Graafland T. , Engberts J. B. F. N. , Weringa W. D. 
Published: May 2005

AbstractThe mass spectra of ten arylsulfonylmethyl arenesulfonates and two arylsolfonylmethyl trifluoromethanesulfonates are discussed. A notable fragmentation of these compounds is the loss of CH2O from the molecular ions. A probable structure for the [M  CH2O]−. ions, as based on the measurement of metastable rations, is given and a fragmentation mechanism leading to this structure is proposed.
The lowest electronic states of the benzoyl ion. A molecular orbital study with configuration interaction
Authors: Bursey Maurice M. , Kao Jar‐Lin , Pedersen L. 
Published: May 2005

AbstractA configuration interaction method of molecular orbital theory shown to be accurate for the calculation of excited state energies in several aromatic systems was applied to the problem of excited states of the benzoyl ion. The excited singlet and triplet states of the benzoyl ion lie at least 3.8 eV and 2.6 eV, respectively, above the ground state. These results are not in agreement with a postulated state 20 kcal above the ground state. On the other hand, the charge distribution in excited states does agree with that postulated for the 20 kcal state. The p‐hydroxy and p‐cyano substituents do not greatly influence the charge distribution between the ring and the carbonyl group in either the ground or lowest excited states.
Isomerisation of hydrocarbon ions:II—Octenes and isomeric cycloakanes: Acollisional activation study
Authors: Levsen K. 
Published: May 2005

Abstract[C8H16]+. molecular ions from alkenes and cycloalkanes differing in their skeletal con‐figuration do not in general isomerise completely to a common structure, except for the molecular ion of n‐propylcyclopentane, the structure of which is identical to that of the normal octene ions. In contrast, decomposing [CnH2n−1]+ fragments are completely or almost completely isomerised after a lifetime of a few μs.
Electron‐impact studies XCV–skeletal rearrangement fragments in the mass spectra of 3,5‐ diphenylisoxazole and 3,5‐ diphenylpyrazole
Authors: Aldous Graham L. , Bowie John H. 
Published: May 2005

AbstractThe ion [C13H9]+ (m/e 165) is produced from the molecular ion of 3,5‐diphenylisoxazole by the process [M  CO  H2CN·] and [M  CO  HCN  H·] and from that of 3,5‐diphenyl‐pyrazole by the eliminations [M  N2H·  C2H2]. These processes have been studied by 2H and 13C labelling. A correlation between photochemical, thermal and electron‐impact decompostions is noted for 3,5‐diphenylisoxazole.
Studies in mass spectrometry. II—A common intermediate in the primary fragmentation process of α‐phenylmethylenecylopropane
Authors: Derocque Jean‐Luc 
Published: May 2005

AbstractThe variation of Z = [(F)+]/[(M)+·] vs electron energy for the loss of H· and CH3· from the molecular ion of 2‐phenylmethylenecyclopropane (I) and α‐phenylmethylenecyclopropane (II) suggests that they both rearrange to a common intermediate before fragmentation occurs. The structure of the intermediate is discussed with regard to the xperimental values found for the Z ratios and to the mass spectra of deuterium labelled compounds.
Electron‐impact studies XCII–Negative ion‐molecule reactions in anhydride systems. Perfluoroacetic anhydride with succinic, maleic and phthalic anhydrides. An ion cyclotron resonance study
Authors: Bowie J. H. , Williams B. D. 
Published: May 2005

AbstractThe trifluoroacetate anion undergoes reaction with succinic, maleic and phthalic anhydrides to yield 1 : 1 adducts. The molecular anions of maleic and phthalic anhydride also undergo reaction with perfluoroacetic anhydride to produce [CF3CO2]−· Maleic anhydride parent ions produce [M + CF3CO·]− ions when allowed to react with perfluoroacetic anhydride.
Stereospecific 1,3 and 1,4 dehydration reactions in the mass spectra of podocarpan‐12‐ and ‐14‐OLS†
Authors: Wahlberg Inger , Karlsson Kerstin , Enzell Curt R. 
Published: May 2005

AbstractSpecific deuterium labelling revealed that podocarpan‐12α‐ and ‐14α‐01, representing conformationally well defined cyclohexanols, eliminate water mainly by stereospecific 1,3 reactions involving cis tertiary hydrogens on electron‐impact. Dehydration of podocarpan‐12ß‐0l, which also involves a cis tertiary hydrogen, occurs almost exclusively by a 1,4 reaction. Subsequent decomposition of the various [M – 18]+· ions was found to lead to different products, thus explaining some of the intensity differences encountered in the lower parts of the spectra of the epimeric podocarpan‐12‐ols and ‐14‐ols.
Mass spectrometry of organic compounds X–Fragementation of 2‐buten‐1‐o1 on electron‐impact
Authors: Kingston David G. I. , Tannenbaum Harvey P. 
Published: May 2005

AbstractThe mass spectra of variously deuterated 2‐buten‐1‐ols (both Z and E) have been examined. Evidence is presented for the formation of the [M – H2O]+· ion via a 6‐membered transition state, and for the occurrence of two distinct reaction pathways for formation of the major ions at m/e 57 and 43.
Substituent effects in mass spectra of monosubstituted benzils
Authors: Richards Kenneth E. , McMaster Blair N. , Wright Graeme J. 
Published: May 2005

AbstractThe mass spectra of a series of thirteenm‐ andp‐substituted benzils have been determined at several ionising voltages below 20 eV and at 70 eV. At ionising voltages up to 5 eV above the ionisation potentials the benzil molecular ions decompose entirely by two pathways to give substituted and unsubstituted benzoyl ions. Fractional intensities of the molecular ion (FM), substituted (FX) and unsubstituted (FH) benzoyl ions were obtained for each benzil as a function of energy from measured ionisation efficiency curves, and ionisation and appearance potentials for all major ions determined from the ionisation efficiency curves by a semilogarithmic method. Various correlations of ion intensity and energy parameters with δ+and δ constants are examined; these are generally poor. Fair correlations are obtained between log (FX/FH) or (AP– AP) and δ or δ+, and these are interpreted in terms of the expected effect of substituents on the stabilities of the product ions in the decompositions. A good correlation is observed between log (FX/FH) and AP· AP; this suggests that substituents affect FX/FHmainly by changing the activation energies for the competing decompositions of the molecular ions. The competitive shift has a marked effect on these appearance potentials so that in this system AP – IP is not a good measure of the activation energy for the primary decompositions.
Fragmentation and rearrangement processes in the high resolution mass spectra of diphenylsilyl compounds
Authors: Ho Benedic T. Y. K. , Spialter Leonard , Smithson Lee D. 
Published: May 2005

AbstractHigh resolution mass spectra of a series of diphenylsilyl compounds, Ph2SiX2(X=H, F, Cl) and Ph2Si(oy)2 (Y=Et, Me, H), were recorded. Results from selected metastable defocusing experiments showed that if X or OY can be readily lost stepwise, the relative abundance of the biphenyl radical rearrangement ion (d) is small; if neutral silicon species such as :SiX2, SiX or :Si(OY)2 are readily eliminated, the relative abundance of the ion d will be large. The ion d originates from both odd‐ and even‐electron ions, thus making the radical site mechanism, which requires a phenyl radical to polarize the other phenyl group, rather unlikely to be an important general driving force. The condensation of phenyl groups could be more appropriately viewed in terms of bond liability and product stability. In the special case of diphenylsilyl catecholate, in addition to geminal cleavage of phenyl groups, complex fragmentation and rearrangement processes were also observed.
MASSENSPEKTROMETRISCHE UNTERSUCHUNGEN ZUR STRUKTUR STABILER [mCH2COOH3]+‐IONEN AUS α,ω‐DICARBONSäREDIMETHYLESTERN
Authors: Schwarz Helmut 
Published: May 2005

AbstractMit Hilfe von Auftrittspotential‐Messungen wird gezeigt, daß die stabilen [M  CH2COOCH3]+‐Ionen aus den Titelverbindungen im Fall von n= 4,5 und 6 eine cyclische Struktur besitzen. Die Bildung freier Carbenium‐Ionen oder Ionen einer isomersen Struktur wird diskutiert.
Mass spectrometric beheviour of some 5,5‐diphenylglycocyamidine and ‐hydantoin derivatives
Authors: Tamás J. , Czira G. , Simig Gy. , Lempert K. 
Published: May 2005

AbstractThe mass spectra and main fragmentation pathways are presented for thirteen 1‐ and 3‐substituted 5,5‐diphenylglycocyamidine and ‐hydantoin derivatives. The principal decomposition routes of these compounds are also of diagnostic value for ascertaining positional isomerism when the substituents are eliminated in the initial stage of fragmentation.
FRAGMENTATION DES AMINO‐2 STEROIDES EN SPECTROMETRIE DE MASSE
Authors: Marazano Christian , Longevialle Et Pierre 
Published: May 2005

AbstractLa fragmentation des diméthylamino‐2 stéroides en spectrométrie de masse est étudiée et des interprétations proposées pour la formation des principaux ions formés. L'étude comparée avac Ie spectre d'un β‐amino‐alcool (OH en 3) permet de déterminer Ia rupture initiale dans Ie mécanisme de formation des principaux ions. Une comparaison est faite entre Ia fragmentation des amino‐3 et celle des amino‐2 stéroides.