Massenspektrometrische Untersuchung von Amiden. IX—Nachbargruppenwechselwirkung Statt Ringkontraktion bei der Fragmentierung von Carbonsäurepiperididen

Ring contractions which are typical for the electron-impact-induced fragmentation of N-acetylpiperidine play only a small part in the fragmentation of piperidides from higher, saturated carboxylic acids. The investigation of ²H labelled compounds as well as energetic measurements (appearance potentials) show that the elimination of CH₃^˙ and C₂H₅^˙ is best rationalised by the assumption of a neighbouring group participation of the amide function.     

Massenspektrometrische Untersuchung von Amiden. IV—Nachbargruppenbeteiligung Bei der Elektronensto-Ssinduzierten Fragmentierung von O-Nitrobenzoesaurepiperidid

The differences in the electron-impact-induced fragmentation of ortho and para- nitrobenzoylpiperidine are connected with neighbouring group participation of the NO₂ group. New oxygen migration, as well as the formation of stabilised radicals by intramolecular interaction of both functions, are only possible with the ortho compound.     

Massenspektroskopische Fragmentierungsreaktionen. IX—Ringkontraktion bei 6- und 7-ringen: eine überischt

The experimental evidence available to substantiate postulated ring contraction processes in 6- and 7-membered perhydro heterocyclics has been reviewed.     

Elektronenstossinduzierte Fragmentierung von Acetylenverbindungen. IX—Struktur der Stabilen [C9H11]+-Ionen aus Isomeren C9H11-Chloriden

The structure of stable [C₉H₁₁]⁺ ions from different model compounds with the molecular formula C₉H₁₁Cl has been estimated by energy measurements. It has further been shown that acetylenic compounds cyclise to form aromatic ions in the range of the appearance potentials.     

Elektronenstossinduzierte Fragmentierung von Acetylenverbindungen—V: Vergleich der Isomeren Naphthyl- und Phenyl-Pentinen-Alkohole

The differences found in the fragmentation pattern of the isomeric naphthyl- and phenyl-pentynen-alcohols have been elucidated by the investigation of ²H- and ¹³C-labelled derivatives. As shown by high resolution mass spectrometry, in the case of the acetylenic compound, the ion [C₉H₇]^⊕ is formed mainly by ketene elimination from the [M – 1]⁺-ion and from the naphthalenes by elimination of acetylene from the benztropylium-ion. The proposed mechanism of CO- and CHO-elimination given for benzylalcohol cannot be transferred to the compounds investigated.     

Die massenspektrometrische Fragmentierung von Neopentylpolyolestern. 1—Pentaerythrittetrafettsäureester

The fragmentation of the homologous fatty acid tetraesters of pentaerythritol (C-2 to C-14) upon electron impact was investigated. The main fragment ions are [M? RCOO]⁺ and [M? RCOOH]⁺, for which cyclic acetal structures are postulated. Subsequent fragmentation was elucidated by ‘direct analysis of daughter ion’ (DADI) measurements and high resolution measurements. Esters of branched fatty acids can be distinguished from esters of n-fatty acids by characteristic ions. Isomeric esters of n-fatty acids cannot be separated by gas chromatography but identification is also possible by mass spectrometry.     

Mechanismus der Amin-eliminierungen bei der Elektronenstoßinduzierten Fragmentierung von 1.3-Diaminopropanen

1,3-Diaminopropanes exhibit strong elimination of amines from the molecular ions upon electron-impact. This is followed by secondary reactions in the course of which a substituent from the C-2 of the propane unit is eliminated and also a N-substituent to a smaller degree. Lowering the electron density at only one nitrogen atom by appropriate substituents causes a decrease in the intensity of both [M–amine]⁺˙ ions. The corresponding fragmentation processes were investigated by means of deuterium labelling.     

Wasserstoffumlagerungen bei der elektronenstoßinduzierten Fragmentierung von Aminoäthern

Due to neighbouring group effects the behaviour under electron impact of amino ethers of the type RO(CH₂)_nNR₁R₂ is distinctly different from that of both simple ethers and amines. In addition to α-cleavages two further primary fragmentations can often be observed, one leading to [M–aldehyde]^+. or [M–ketone]^+. ions, the other (with n≥3) giving [M–R]⁺ ions. Both processes involve hydrogen rearrangements which were investigated by means of deuterium labelling. Their importance is strongly dependent upon the nature of the substituents R, R₁, R₂ and upon the length (n) of the carbon chain between the heteroatoms. This dependence can easily be explained by the fragmentation mechanisms put forward.     

Nachbargruppeneffekte bei der Massenspektrometrischen Fragmentierung von Amino-benzylalkoholen

The fragmentation behaviour of a series of substituted aminobenzylacohols has been investigated by means of high and low resolution mass spectroscopy, metastable defocusing and deuterium labelling. o-, m- and p-Isomers exhibit characteristic fragmentation patterns that are of considerable diagnostic value in the structure determination of this class of compounds.     

Notiz zur elektronenstoßinduzierten Ringkontraktion von Cycloalkanonen und zur Struktur der -Ionen

Collisional activation demonstrates that the cyclooctanone cation does not isomerize to ionized 2-ethylcyclohexanone prior to ethylene elimination. In addition evidence is presented that the structures of the m/e 98 ions formed by single and by double McLafferty rearrangement in some cycloalkanones differ according to the structure of their precursors.     

Bei der Papierchromatographie von Zuckern

Ohne Zusammenfassung     

Bei der Standardbestimmung von Chlorophyll

Ohne Zusammenfassung     

Bei der Papierchromatographie von Digitoxin

Ohne Zusammenfassung     

Bei der Schnellanalyse von Korund

Ohne Zusammenfassung     

Zum Mechanismus Massenspektrometrischer Fragmentierungsreaktionen. XVI—hydrid-Wanderungen bei der Fragmentierung von αω-Dimethoxyalkyl-Ionen

The isomerization and fragmentation of α,ω-dimethoxyalkyl ions a (CH₃OCH₂(CH₂)_n- CH⁺OCH₃, n = 1-6) has been investigated by deuterium labelling. It is shown that a isomerizes to ion a' by hydride transfer from the ω-CH₂ group to the positive charge at the α-C-atom before elimination of methanol. Both methoxy groups are lost as methanol. The amount of isomerization can be deduced from alkene elimination from [a ? CH₃OH]+ ions in deuterated derivatives of a. On average at 70 eV three rearrangement steps involving hydride transfer are observed.     

Bei der Untersuchung von Zirkonmineralien

Ohne Zusammenfassung     

Bei der Papierelektrophorese von Casein

Ohne Zusammenfassung     

Bei der Bestimmung von Ergothionein

Ohne Zusammenfassung