H. Budzikiewicz

Massenspektrometrie und IHRE anwendung auf strukturelle und stereochemische probleme—LXVII: Zum retro-diels-alder-zerfall organischer moleküle unter elektronenbeschuss☆☆☆

Zusammenfassung Die Zerfallsreaktion organischer Molekule unter Elektronenbeschuss, die formal einer retro-Diels-Alder-Reaktion entspricht, wird diskutiert. Im Falle des einfachsten Vertreters, Cyclohexen, wird versucht, an Hand von thermodynamischen Daten die fur den Zerfall notwendige Energie zu berechnen, und es wird gezeigt, dass auf Grund dieser Uberlegungen Voraussagen uber die bevorzugte Bildung eines ionisierten En- oder Dien-Fragmentes gemacht werden konnen, die selbst auf komplizierte Molekule wie Steroide und pentacyclische Triterpene anwendbar sind. Beispiele aus verschiedenen Verbindungsklassen werden gegeben, die den diagnostischen Wert dieser Zerfallsreaktion illustrieren.

Pyrroles and related compounds. X.

Abstract The molecular ion nearly always produces the strongest peak in mass spectra of porphyrins. The macrocyclic nucleus is remarkably stable and fragmentation gives mainly “benzylic” ions. In derivatives of porphin this involves cleavage at the bond once removed from the macrocycle, but in chlorins the entire substituent is lost from the reduced “pyrrole” ring. Methyl esters of chlorins derived from chlorophyll lose directly 147 and 159 mass units in complex processes marked by strong metastable peaks. All the spectra contain a prominent series of peaks from doubly charged ions; a novel feature is loss of ketene from propionate side-chains.Abstract The molecular ion nearly always produces the strongest peak in mass spectra of porphyrins. The macrocyclic nucleus is remarkably stable and fragmentation gives mainly “benzylic” ions. In derivatives of porphin this involves cleavage at the bond once removed from the macrocycle, but in chlorins the entire substituent is lost from the reduced “pyrrole” ring. Methyl esters of chlorins derived from chlorophyll lose directly 147 and 159 mass units in complex processes marked by strong metastable peaks. All the spectra contain a prominent series of peaks from doubly charged ions; a novel feature is loss of ketene from propionate side-chains.

Massenspektroskopie und IHRE anwendung auf strukturelle und stereochemische probleme—LXVIII: Massenspektroskopische untersuchung der inhaltstoffe von haschisch☆☆☆★

Zusammenfassung Die Massenspektren einer Reihe von Haschischinhaltstoffen und ihren Derivaten werden diskutiert. Fragmentierung erfolgt bevorzugt im alicyclischen Teil der Molekule, wobei der Benzolring als ladungsstabilisierendes Element fungiert. Zahlreiche fur Monoterpene typische Umlagerungen konnen beobachtet werden.

Mass spectrometry in structural and stereochemical problems—XXXIX : Tropane alkaloids☆☆☆

Abstract The mass spectra of a series of tropane alkaloids have been measured and the major fragments identified, largely through the use of deuterium or substituent labelling. The principal bond fissions follow the paths laid down earlier for simple amines, cyclic ketones and alcohols, thus affording characteristic fragmentation patterns, which may prove useful in the characterization of unknown members of this class.

Mass spectrometry in structural and Stereochemical problems—XXXIV : Aromatic methyl and ethyl ethers☆☆☆

Abstract The behavior under electron impact of a series of aromatic methoxy and ethoxy compounds has been observed. The more common fragmentation processes are interpreted and in some cases the differences among spectra of positional isomers can be explained.

Studies on indian medicinal plants—VI : Structures of glycosmicine, glycorine and glycosminine, the minor alkaloids from Glycosmis arborea (roxb.) DC☆

Abstract On the basis of physical methods, three minor alkaloids from Glycosmis arborea (Roxb.) DC., viz. glycosmicine, glycorine and glycosminine have been assigned the following structures: 1-methyl-2-keto-1,2-dihydro-4-quinazolone (II), 1-methyl-4-quinazolone (V) and 2-benzyl-4-quinazolone (XIII), respectively. It has been observed that the alkaloids exist in equilibrium forms. The structures have been confirmed by synthesis in each case. The mass spectra and the infra-red spectral characteristics of the quinazolone derivatives have been discussed in detail.

Pyrroles and related compounds—X : Mass spectrometry in structural and stereochemical problems—XC Mass spectra of linear di=, tri- and tetrapyrrolic compounds☆☆☆

Abstract Mass spectra of 55 di-, tri- and tetra-pyrroles (Table 1) are recorded (Table 2); these include prodigiosin and five bile pigments. The factors affecting the various types of cleavages observed are discussed. Fragmentations of the side-chains usually follow similar patterns to those observed with mono-pyrroles, although, with pyrromethanes, cleavage of alkyl or carboxylic ester groups neighbouring the methylene bridge may be favoured by the formation of pyrromethene-like species or tricyclic pyrromethenes respectively. Cleavages between the nuclei are profoundly affected by the nature of the linkage involved e.g. pyrromethanes and pyrroketones undergo fairly ready inter-nuclear fragmentation, whereas the pyrromethenes (as might be expected) are much more stable, and cleavage of pyrrole-pyrrole bonds (as in prodigiosin) appears to be a very unfavourable process.

Determination of mass spectra of non-volatile substances

Ein einfaches Glas-Einlass-System wird beschrieben, das die direkte Einführung von organischen Substanzen in die Ionisationskammer eines Massenspek trometers gestattet. Es ist somit möglich Massenspektren von Substanzen zu bestimmen die man bisher nicht aufnehmen konnte. Beispiele werden angeführt.

Mass spectrometry in structural and stereochemical problems]—XCII : Further studies on the McLafferty rearrangement of aliphatic ketones

Abstract Energetic factors governing the McLafferty rearrangement of ketones are discussed. Through the use of deuterium labeled n-butyl-isobutyl ketones it is shown that when two competing alternatives for the transfer of a hydrogen atom from a γ-position are available abstraction of a secondary hydrogen will be highly favored over a primary one. Other effects, such as the stability of the final products and preferred conformations must also be taken into account. The itinerant hydrogen atoms in the double McLafferty rearrangement of aliphatic ketones, which hitherto have not been investigated, are shown to be principally the γ- and γ′-hydrogen atoms.

Massenspektroskopie und ihre Anwendung auf strukturelle und stereochemische Probleme, 44. Mitt.: Das Fragmentierungsverhalten monocyclischer Ketone

Die Massenspektren einer Reihe monocyclischer Ketone sind gemessen worden. Durch Vergleich der Spektren mit denen deuterierter Derivate ist es moglich, plausible Mechanismen fur die Bildung charakteristischer Fragmente abzuleiten.