Elektronenstossinduzierte fragmentierung von polymethylbenzaldehyden—III: Bildung und Zerfall des Formyltropylium-ions aus Dimethylbenzaldehyd

The electron-impact-induced formation of the very unstable ‘formyltropylium-ion’ from dimethylbenzaldehyde can be explained by the mechanism of a vinylogous α-cleavage.     

Massenspektrometrische Untersuchung von Amiden. VI—Mechanismus der Methyl-Abspaltung aus Crotonsä;urepiperidid

By the investigation of ²H labelled compounds, it has been established that in the case of crotonoyl piperidyl only the hydrogens of the methyl group participate in the elimination of CH₃·.     

Massenspektrometrische Untersuchung von Amiden: III—Intramolekulare Nucleophile Substitution bei der Methyl-Abspaltung aus Crotonsaurepiperidid und Vinylogen Derivaten

The methyl cleavage from piperidides of type CH₃(CH?CH)_nCONC₅H₁₀ with n = 1 to 3 does not proceed via ring contraction as shown earlier with n = 0. The fragmentation can be formulated with the concept of neighbouring group participation of the amide function which leads to a cyclic transition state. Investigations with a ²H-labelled compound in the case of n = 1 as well as energy measurements (AP, IP, E_k) agree with this assumption.     

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.     

Elektronenstossinduzierte fragmentierung von acetylenverbindungen — VII: Ein vergleich der massenspektren von offenkettigen und aromatischen C9H12O-alkoholen

The principal difference in the electron impact induced behaviour of primary and secondary acetylenic alcohols and the corresponding isomeric aromatic compounds consist in a very easy isomerisation of the open chain compounds to ketones before fragmentation is involved, while with aromatics this behaviour is much less pronounced as here the hydrogen transfer is combined with a loss of the aromaticity.     

Darstellung und Molekülstrukturen von oligofunktionalen Dirheniumcarbonylderivaten aus Dirheniumnonacarbonylphosphan

Preparation and Molecular Structures of Oligofunctional Dirhenium Carbonyl Derivatives from Dirhenium Nonacarbonylphosphane Starting with dirheniumdecacarbonyl, one CO-Ligand was eliminated oxidatively and substituted by the labile acetonitrile ligand. As an intermediate eq-Re₂(CO)₉NCCH₃ was received. The reaction of this labilised carbonyl with tris(trimethylsilyl)phosphine and subsequent methanolysis gave ax-Re₂(CO)₉PH₃, which was isolated and characterized for the first time. Photochemical and thermal reaction of ax-Re₂(CO)₉PH₃ led to the new bi- and trinuclear complexes Re₂(μ-H)(μ₃-PHRe(CO)₅)(CO)₈, Re₂(μ-PH₂)₂(CO)₈ and Re₂(μ-H) · (μ-PH₂)(CO)₈, which were characterized by IR-, ¹H- and ³¹P-NMR spectroscopy. The structures of ax-Re₂(CO)₉PH₃, Re₂(μ-H)(μ₃-PHRe(CO)₅)(CO)₈ and Re₂(μ-PH₂)₂(CO)₈ were confirmed by single-crystal X-ray analysis. ax-Re₂(CO)₉PH₃ has a very short Re? P bond length of 228(2) pm.     

Massenspektrometrische Untersuchung von Amiden X—Notiz zum Mechanismus der H-Abspaltung aus N,N-Dimethylbenzamid

The genesis of the [M? H]⁺ ion from N, N-dimethylbenzamides proceeds only via an interaction of the amido group with the hydrogens in the ortho-Position. The other hydrogen atoms are not involved in the fragmentation.     

Elektronenstossinduzierte Fragmentierung von Acetylenverbindungen—VIII:. Struktur der stabilen und instabilen Ionen [C9H9]+ aus isomeren C9H10-Kohlenwasserstoffen

The appearance potentials of [C₉H₉]⁺ have been estimated and the enthalpy of formation, calculated from the data, is correlated with different structural proposals. Open chain structures can be eliminated in favour of aromatic ones (vinyltropylium or indanyl cation). The structure of the unstable [C₉H₉]⁺ ions is investigated by means of ¹³C-labelled compounds. The results are also in agreement with the acceptance of aromatic structures.     

Zum Mechanismus der Aziridinsynthese aus 2-Azidoalkoholen und Triphenylphosphin

On the Mechanism of the Aziridine Synthesis from 2-Azido-alcohols and Triphenylphosphine The reaction of selected 2-azido-alcohols, their pivalates, and methanesulfonates with triphenylphosphine was investigated. It is shown that the formation of aziridines from 2-azido-alcohols proceeds via 1,3,2λ⁵oxazaphospholidines. Furthermore, the first synthesis of the unsubstituted acenaphtene-1,2-imine is described.     

Mechanismus der elektronenstossinduzierten Äathylenabspaltung aus dem Ion [C9H11]+ aus 2,5-Dimethylbenzylbromid

By the investigation of ¹³C-labelled dimethylbenzylbromide, it has been shown that the [M – Br]⁺ ion isomerises to a dimethyltrophylium cation.     

Synthese von derivaten der cinchona-alkaloide—XXXII Synthese von dihydrocorynanthean und 3-epidihydrocorynanthean aus cinchonin

Starting from cinchonine, 3-epidihydrocorynantheane was synthesized through 2′-oxohexahydrocinchonine. Quinine was transformed into 10-methoxydihydrocorynantheane by the same reaction steps. In both cases, it was found that Oppenauer oxidation of the secondary hydroxyl group at quinine-numbering C-9 was accompanied with no configurational change at the neighboring C-atom, which originated from C-8 in quinuclidine moiety. 3-Epidihydrocorynantheane was converted to dihydrocorynantheane by oxidation with mercuric acetate and then sodium borohydride reduction.     

Organische Schwefelverbindungen—IV: Elektronenstossinduzierte Redoxreaktion von ortho-Nitrothiobenzoesäure-S-p-tolylester

The electron-impact fragmentation of S-p-tolylester of nitrothiobenzoic acid leads to a previously unknown rearrangement in the case of the ortho compound. This consists of an intra molecular redoxreaction with oxygen transfer from the o-nitro group onto the sulphur of the thiol ester group. The position of the nitro group is not only an essential influence on the fragmentation pattern, but also of dramatic importance in determining the lifetime of the molecular ion.