Reaktionen von 2- und 3-phenylsubstituierten Alkylakyliden-iminium-Ionen in der Gasphase. 5. Mitteilung über stossinduzierte Fragmentierungen von felddesorbierten Kationen

Reactions of 2- and 3-Phenyl Substituted Alkylalkylidene Iminium Ions in the Gas Phase The collision-induced fragmentations of 2- and 3-phenyl substituted alkylalkylidene iminium ions are reported. Besides the homolytic cleavage of the azaallyl bond a nucleophilic attack of the unsubstituted phenyl group at the iminium function is observed in the gas phase, yielding carbonium ions such as cyclopropanspirobenzenium ( 3 ), indanylium ( 10 ) and indenylium ions ( 11 ).     

Neues über den Mechanismus der retentiven Substitution am Dreiring von Propellanen. Vorläufige Mitteilung

New results concerning the mechanism of retentive substitution at the three membered ring of propellanes The reaction of the endo- and exo-bromide 1a and 1b with acetate ion in aprotic polar solvents carried out at high concentrations of 1 furnishes the dimeric dehydro-halogenation products 3a and 3b , the structures of which are determined by x-ray crystallography (Fig. 1). The formation of 3a and 3b as well as of the products 2 of a retentive substitution process can be explained by assuming that the strained benzo-tropones 4 are intermediates. Their high barrier to inversion is confirmed by π-SCF-molecular mechanics calculations.     

Reaktionen von Glutaminsäuredimethylester im Massenspektrometer. 21. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen

The mass spectral fragmentation of dimethyl glutamate ( 1 ) and its deuterated derivatives 1a , 1b and 1c has been investigated. By loss of a methoxycarbonyl group from the molecular ion an ion of m/e 116 is generated. The latter splits off methanol (m*), the resulting fragment of m/e 84 giving raise to the base peak of the spectrum. Only part of the hydrogen transferred to the leaving group originates from thc amino group, as was suggested earlier [2] [3]. Basing on experiments with deuterated compounds we propose an additional mechanism for the reaction, i.e. hydrogen transfer from C(3) to methoxyl. The fragment generated by both processes is most likely to be a pyrrolinonium ion. Thermal side reactions in the mass spectrometer (formation of pyroglutamic acid ester) followed by fragmentation may lead to the same ion. – The mechanisms discussed are supported by the mass spectral fragmentation of N-acetyl-glutamic acid diesters 3 , 3a , 3b and 3d and of the N, N-dimethyl derivatives 4 and 4a . – The fragmentation reactions investigated are similar to some of 1,3-trimethylenediamine derivatives [7]. This means that there are parallels in the mass spectral fragmentation of difunctional compounds irrespective of the nature of the functional groups.     

Massenspektrometrische Identifizierung und Synthese isomerer und homologer Spermidin- und Spermin-Derivate. 25. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen. 161. Mitteilung über Alkaloide

Synthesis of isomeric and homologous spermidine and spermine derivatives and their identification by mass spectrometry. The structure of homologous and isomeric spermidines and spermines follows from mass-spectroscopical analysis of their peracetyl (see text, footnote 3) (Table 1) or tosyl-acetyl (Table 2) derivatives. In the case of the peracetyl compounds, triads of peaks are recorded which, according to the number of methylene groups between the nitrogen atoms, show mass numbers characteristic for each of the substances (Scheme 1, ions b , d , e and c ). On the basis of cyclic ions of type f (Scheme 2), occurring in the mass spectra of N-acetyl derivatives, tosylated on a secondary amino nitrogen atom, deductions can be drawn as to the number of methylene groups between neighbouring tosylated and acetylated nitrogen atoms in these compounds.     

Kinetische Untersuchungen über Substitutionsreaktionen an Metallkomplexen. 9. Mitteilung [1]. Kinetik und Mechanismus der Reaktion von Hexamethylborazolchrom-tricarbonyl mit tertiären Phosphinen und Phosphiten [2]

Hexamethylborazolechromium tricarbonyl B₃N₃(CH₃)₆ Cr(CO)₃ reacts with tertiary phosphines and phosphites under surprisingly mild conditions by cleavage of the ring-to-metal bond. For L = trialkylphosphines and trialkyl- or triaryl-phosphites, compounds of the general composition cis-Cr(CO)₃L₃ are formed, whereas for L = triphenyl- and tricyclohexyl-phosphine the complexes trans-Cr(CO)₄L₂ are obtained. The kinetics of the reaction of B₃N₃(CH₃)₆ Cr(CO)₃ with phosphites P(OR)₃ (R = CH₃, C₂H₅, C₆H₅) have been studied by means of spectrophotometric methods. The second-order rate law indicates a primary, rate-determining attack of the phosphite to either the metal atom or the ring ligand of the borazole complex. This attack is favoured by an extremely low activation energy. The mechanism of the substitution process is discussed in detail, and the reactivity of the hexamethylborazole compound is compared with that of other half-sandwich type complexes.     

Nachbargruppenbeteiligung bei massenspektrometrischen Fragmentierungsreaktionen: Spermin-Derivate. 18. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen

The mass spectral behaviour of tetraacetyl spermine ( 2 ) has been investigated. The fragmentation reactions are characterized by the neighbouring group participation of the amide nitrogen atoms. Only a few reactions can be explained by usual pathways (α-cleavage, onium reactions). Most of the fragment-ions are formed by neighbouring group participation:

• 1 [M-COCH₃]⁺-Ion.
• 2 Breakdown of one of the two 1,3-diaminopropan moieties: m/e 242, 256, 268. This type of fragmentation is characteristic for all acetylated 1,3-diaminopropan-derivatives e.g. triacetylspermidine.
• 3 Expulsion of a neutral amine: m/e 169.
• 4 S_Ni-type reactions, by which cyclic ions are formed: m/e 100.

     

SN-2-artige massenspektrometrische Fragmentierungen bei substituierten N-Alkylpiperidinen. 10. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen [1]

An S_N2-type fragmentation was observed on mass spectrometric analysis of N-(ω-X-alkyl)-2-alkylpiperidines (X = NRCOR′,  CONH₂,  COOR,  NH₂). The molecular ion after loss of the 2 alkyl substituent on the piperidine ring may eject the neutral piperideine on attack of the substituent X on the α-carbon of the N-substituted alkyl-chain. Through this process a cyclic fragment ion is formed. The influence of its ring size and of the substituent X on the stability of this fragment was investigated. The S_N2 reaction is favoured in the case of production of five- and six-membered rings.     

Der massenspektrometrische Verlust von Vinylalkohol aus 1-Amino-3-aryloxy-2-propanolen. 24. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen

Loss of vinyl alcohol from 1-amino-3-aryloxy-2-propanols under electron impact Under electron impact compounds of type 1 (see Scheme 1) split off 44 mass units from the molecular ion. This unusual reaction was studied using derivatives and deuterium labelled compounds. It could be demonstrated that for this fragmentation reaction 16 is the important structural feature from which H₂(C3)?C(2)HOH (44 mass units) is lost. The preferred reaction mechanism involves a transition state in which four members of the side chain are involved (Scheme 2, mechanism 2).     

Weitere Untersuchungen über den Mechanismus der reduktiven Spaltung von Azoverbindungen

The experimental results of our earlier investigation of the azodye bleach mechanism are interpreted in a revised manner. The reductive cleavage of methylorange by a dihydroquinoxaline proceeds in two steps. In the medium pH-range the first step (production of the hydrazo derivative) is slower (and not faster, as considered before) than the second (reductive splitting of the hydrazo derivative). In strongly acid solution this relation is reversed. The rate of disproportionation of the hydrazo derivative of methylorange is proportional to the concentration of the protonated hydrazo compound. For this reaction a two step mechanism is proposed in which a molecule of hydrazo compound is cleaved in a rate determining first step to an oxidizing particle and an amine molecule. In the following fast reaction the oxidizing intermediate attacks a second hydrazo molecule yielding methylorange and a further amine molecule. Based on this reaction sequence an azodye bleach mechanism is formulated which is able to explain the kinetics of the reductive cleavage of methylorange by a 1, 4-dihydroquinoxaline at any pH value. The azodye bleach mechanism is much more complex if the 1,4-dihydroquinoxaline used is able to form a radical or to tautomerize. The resulting reaction kinetics are discussed.     

Beitrag zum Mechanismus der Sorption von Molekularkolloiden an festen Stoffen

Zusammenfassung Bei der Sorption von Methylenblau anTierkohle wurde festgestellt, da\ bei allen untersuchten Konzentrationen und Temperaturen dieEldridgesche Gleichung gültig ist. Die Geschwindigkeitskonstante ist ab einer Konzentration 0,08 %. der Methylenblaul?sung linearproportional zur Konzentration der L?sung. Die Gültigkeit derEldridgeschen Gleichung und die berechnete Aktivierungsenergie erlauben, einen Mechanismus der Sorption zu erschlie\en: Es handelt sich um eine Diffusion der Kolloidteilchen der L?sung in Richtung der auf den K?rner adh?rierenden Schicht, deren Konzentration abh?ngig ist von der Temperatur und dem Anfangsgehalt der L?sung, der w?hrend der Sorption konstant bleibt, da die koagulierenden Kolloidteilchen sich aus Kolloidteilchen der L?sung erg?nzen. Nach einer für jeden Fall (Konzentration, Temperatur) festliegenden Verdünnung der Anfangsl?sung findet keine Sorption mehr statt.     

Beitrag zum Mechanismus der Sorption von Molekularkolloiden an festen Stoffen

Zusammenfassung Bei der Sorption Methylenblau von Alumina nachBrockmann wurde eine Teildesorption der w?hrend der ersten Sekunden sorbierten Menge festgestellt, die auf eine chemische Alterung des Oxyds zurückgeführt werden kann. Durch die gefundenen Werte der Aktivierungsenergie der Alterung ergibt sich, da? das in Alumina nachBrockmann erhaltene Al₂O₃ gewi? mit demselben Mechanismus wie das elektrolytisch gewonnene γ₁ γ₂ Al₂O₃ (2–5) altert. Bei 0° C altert das Oxyd nicht. Das Auftreten dieses Ph?nomens bei der chromatographischen Analyse mit Alumina nachBrockmann und die M?glichkeit, dieses Ph?nomen durch Erhitzen zu beeinflussen oder zu eliminieren (0° C), führen zu neuen M?glichkeiten bei oben genannten Analysen. Derartige Untersuchungen laufen schon. Für 0° C wurden Messungen der Sorption für verschiedene Konzentrationen von Methylenblau durchgeführt und festgestellt, da? in allen F?llen dieEldridge- sche Gleichung gültig ist. Die aus den Messungen gefolgerte Aktivierungsenergie der Sorption, ?hnlich wie bei der Sorption derselben Substanz an Tierkohle, zeigt, da? in beiden F?llen derselbe Mechanismus wirksam ist: Das geschwindigkeitsbestimmende Ph?nomen ist die Diffusion der Kolloidteilchen in der Richtung der adh?rierenden Schicht der K?rner des Absorbens.     

Nachbargruppeneffekte bei massenspektrometrischen Fragmentierungsreaktionen: substituierte 1,3-Diaminopropan-Derivate. 17. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen

The mass spectrometric behaviour of the 1,3-diaminopropane derivative 4a (3,7-diacetyl-3,7-diazadodecane) was investigated with regard to the fragmentation reactions of N, N′, N″-triacetylspermidine ( 1 ), as model for the 1,3-diaminopropane part. It was established that the degradation reactions in 4a and 1 are essentially the same and mainly due to the interaction of two N-acetyl groups. Thereby it is established that the most important mass spectrometric fragmentation reactions of spermidine derivatives take place within the 1,3-diaminopropane unit and are independent of the influence of further N-atoms in the molecule. An ion (m/e 143) was found in the fragmentation pattern of N, N′, N″-triacetylspermidine whose formation can be explained by interaction of all three N-acetyl groups. The corresponding ion was not found, in the spectrum of 4a , with only two N-acetyl groups, thereby confirming the earlier hypothesis.     

Zur Berechnung der Aciditätskonstante von Sorbit aus der Sorbitolysenkinetik von Reaktivfarbstoffen. 4. Mitteilung über reaktionsmechanistische Untersuchungen an Reaktivfarbstoffen

The first acid dissociation constant of sorbitol is redetermined (PK_a = 13.00; 60°).     

Zur Photochemie von Allylaryläthern. 55. Mitteilung über Photoreaktionen

The photochemical reactions of different allyl aryl ethers (Scheme 3) were investigated in hydrocarbons (Chap. 3.1) and in alcoholic solvents (Chap. 3.2). The composition of the photoproducts depended very much on the nature of the solvent. Irradiation (3–95 h) of different methyl substituted allyl aryl ethers ( 1, 3, 5, 7 and 11 ) with a low pressure mercury lamp (λ_Emiss. = 254 nm; 6 or 15 Watt) under argon (quartz vessel) resulted in the formation of 2-, 3– and 4-substituted phenols, dienones and products of consecutive reactions (Tables 1–4 and 6). The results suggested that all products were formed by homolytic cleavage of the C? O bond in the singlet state of the ethers to intermediate radical-geminates (Scheme 5) followed by radical recombination of the two fragments. No products were formed by concerted processes (Table 5, Schemes 5 and 6). Upon irradiation of allyl aryl ethers lacking alkyl substituents at position 4 ( 1 and 5 ) in protic solvents, mainly 2- and 4-allylated phenols were obtained (Tables 1 and 4); 3-allylated phenols were formed only in small amounts (0.02%). However, in aromatic hydrocarbons or cyclohexane 3-allylated phenols were obtained from 1 , 5 and 11 in significant amounts (3–11%; Tables 1, 4 and 6). E.g., upon irradiation of allyl-2,6-dimethyl-2,4-cyclohexadien-1-one ( 6 ) besides 3- and 4-allyl-2, 6-dimethyl-phenol ( 23 and 24 ). Irradiation of 5 in methanol afforded 23 and 6 only in traces, whereas 24 was the main product.