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.     

Allgemeine Basenkatalyse der Azokupplung von o-Diazophenolen. 19. Mitteilung zur Kenntnis der Azokupplungsreaktion

1. The kinetics and the mechanism of the diazo coupling reaction of 2-diazophenol-4-sulphonic acid with 1-naphthol-2-sulphonic acid have been investigated at 0° and ionic strength I=0.45. 2. The pK_a-value of the hydroxyl group in 2-diazophenol-4-sulphonic acid has been determined: pK_a=- 0.04 ± 0.10. It is the diazonium-phenolate anion which actually enters into the diazo coupling reaction. 3. The reaction is subject to general base catalysis. It is shown that no intermediate is enriched during the reaction at pH 11.3–11.6 which proceeds by a two-step mechanism with a steady state intermediate.     

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.     

Elektronendonator-Akzeptor-Komplexe von Diazonium-Ionen und die Struktur von stabilisierten Diazonium-Salzen. 20. Mitteilung zur Kenntnis der Azokupplungsreaktion

1. In 0.1N HCl/H₂O, o- and p-nitrobenzenediazonium ions rapidly form a complex with 2-naphthol-6, 8-disulphonic acid anions. Visible and NMR, spectra show that it has the structure of a charge-transfer complex (π-complex). The latter is probably an intermediate in the electrophilic aromatic substitution (diazo coupling reaction). 2. Diazonium ions form charge-transfer complexes with naphthalene, 1-methylnaphthalene, naphthalene-1-sulphonic acid, 1-naphthyl-methanesulphonic acid and also 2-naphthol-1-sulphonic acid. The equilibrium constants of all these complexes have been determined. 3. The stabilisation of diazonium salts by arylsulphonic acids with regard to decomposition is due to charge-transfer complex formation and not to formation of diazosulphonates as assumed by former investigators. The sulphonic group is not essential for the stabilisation. 4. Charge-transfer complex formation decreases the electrophilicity of the diazonium ion (rate of diazo coupling reaction) only slightly.     

Methode zur Konstitutionsaufklärung der Reaktionsprodukte der Umsetzung von Cellulose mit Formaldehyd. 18. Mitteilung über textilchemische Untersuchungen [1]

(1) A method is described which allows the elucidation of the structure of cotton cross-linked with formaldehyde. It consists of a permethylation process (5 methylations with dimethyl sulphate and sodium hydroxide in dimethyl sulphoxide, followed by two exchange methylations of the formalised sodium cellulosate with methyl iodide in n-butanol), hydrolysis of the product in 72% sulphuric acid to the respective methylated glucoses, reduction of the mixture of glucoses to the respective sorbitols, blocking of all free hydroxyl groups by acetylation, trifluoroacetylation or formation of trimethylsilyl ethers, and vapour phase chromatographic separation of the derivatives. (2) It is shown that after permethylation practically no free hydroxyl groups can be detected and that scarcely any replacement of methylene or oxymethylene cross-links by methyl groups has taken place. With the exception of losses in filtration of the permethylation product, all stages of the process proceed on an almost quantitative basis.     

Methode zur Konstitutionsaufklärung von Celluloseformalen von niedrigem Substitutionsgrad. 29. Mitteilung über textilchemische Untersuchungen

A method is described which allows the determination of the hydroxyl group(s) in glucose units of cellulose which react with formaldehyde at low degrees of substitution (0.2 to 1.5% CH₂O on cellulose). It consists of permethylation of the cellulose by a sequence of two methylations with dimethylsulfate and NaOH (without solvent) followed by 2 exchange methylations with methyl iodide and sodium n-butoxide and further steps described earlier [2]. The results demonstrate that the use of the new permethylation method leads to a loss of material of less than 5%.     

Untersuchungen über die Kinetik und den Mechanismus der Bindung von Schwefeldioxid und Stickoxiden durch gasförmiges Ammoniak

Studies on Kinetics and Mechanism of the Reaction of Sulphur Dioxide and Nitrogen Oxides with Gaseous Ammonia It was found that depending on the partial pressure of SO₂, H₂O, and NH₃ different solid products were formed. Formation of the product containing the smallest amount of the substrate of the lowest partial pressure is favoured. The measured stability limits of the solid products confirmed the former thermodynamic calculations. The conditions for effective binding of NO_x with ammonia were established.     

Selbstorganisation von Chinodimethanen über kovalente Bindungen,Mitteilung III,Untersuchungen zur Herstellung von Nanostrukturen

Self‐Assembly of Quinodimethanes through Covalent Bonds. Part III. Investigations on the Preparation of Nanostructures As part of our studies on the tetramerization of quinodimethane 1 to the macrocyclic compound 2 , the influence of substituents on this reaction was investigated. It was found that a large range of substituents such as 2‐phenylethyl, 2‐(4‐methoxyphenyl)ethyl, 2‐(4‐fluorophenyl)ethyl, 2‐[4‐(tert‐butyl)phenyl]ethyl, and 2‐[4‐(2‐phenylethyl)phenyl]ethyl, attached at positions 2 and 7 of 9H‐fluorene, do not prevent the tetramerization. The key step in the formation of the macrocylic compounds 13a – e is the debromination of 12a – e with mercury to the corresponding quinodimethanes which undergo a self‐assembly forming 13a – e in high yields. To study the conjugative influence of substituents on tetramerization, the effect of the hex‐1‐ynyl groups at positions 3 and 6 of the 9H‐fluorene rings was investigated. In this case, the corresponding macrocycle 17 was generated by the reaction of diol 16a with SnCl₂. Although the expected tetramerization to 17 occurred, the yield was lower than in the case of 13a – e , due to the sensitivity of the product.     

Beitrag zum Mechanismus der stossinduzierten Fragmentierungen von quaternären Stickstoffverbindungen. 2. Mitteilung über stossinduzierte Fragmentierungen von felddesorbierten Kationen

Mechanistic studies on the collision-induced fragmentations of quaternary ammonium ions The collision-induced fragmentation behaviour of field desorbed quarternary ammonium ions has been investigated. A main reaction of these ions is the cleavage of the N? C bond accompanied by hydrogen rearrangement, i.e. alkane loss from the tetraalkyl substituted ammonium ions of the iodides 1, 2 and 3 , respectively, Deuterium labelling indicates that the hydrogen transfer to the leaving group occurs to the extent of about 80% from the α-position and about 20% from the other positions of an alkyl group. Pronounced heterolytic cleavage of the N? C bond is observed in the benzyl substituted ammonium ion of 4 . The β-phenylethyl substituted ammonium ion of 5 shows a homobenzylic heterolysis, possibly yielding the phenonium ion j.     

Der [M+11]+-Pik in den Massenspektren von Diaminen 38. Mitteilung über massenspektrometrische Untersuchungen

The [M+ U]⁺-Peak in the Mass Spectra of Diamines The mass spectra of di- and polyamines containing a 1,2-ethandiamine or a 1,3-propandiamine unit are quite often characterized by [M+ 1l]⁺-peaks. It is demonstrated that these peaks correspond to a fragment-ion formed by loss of H. from a formaldehyde-condensation product (e. g. 15) or by loss of CH³. from a acetaldehyde-condensation product (e. g. 16 ) with the diamine. The aldehydes are usually impurities in solvents (especially methanol) used by chromatography, synthesis etc. of the diamines.     

Über den Mechanismus der Cope-Umlagerung

On the Mechanism of the Cope Rearrangement The rates of the Cope rearrangement of 2,5-dicyano-3-methyl-hexa-1, 5-diene ( 12 ), (E)- and (Z)-2, 5-dicyano-hepta-1,5-diene ((E)- and (Z)- 14 ) as well as of 2, 5-dimethoxycarbonyl-3-methyl-hexa-1,5-diene ( 13 ) and (E)- and (Z)-2,5-dimethoxycarbonyl-hepta-1,5-diene ((E)- and (Z)- 15 ) were measured in decane solution in the temperature range of 50 to 150° (see Tables 5 and 8 to 12). A detailed English summary of this work is given in [1 b].     

Beitrag zur massenspektrometrischen retro-Diels-Alder-Reaktion: 1,2,3,4-Tetrahydrophenanthren. 35. Mitteilung über massenspektrometrische Untersuchungen

Contribution to the Mass Spectral retro-Diels-Alder Reaction: 1,2,3,4-Tetrahydrophenanthrene [1,4-¹³C]-1,2,3,4-Tetrahydrophenanthrene (1) was synthesized starting from [1,4-¹³C]-succinic acid. The mass spectral behavior (EI./MS., 70eV) of 1 is very similar to that of tetraline [2] concerning its loss of ethylene from the molecular ion. Similarly the fragmentation reaction of the synthetic precursors, ketones 7 and 8 , seems to partly undergo a carbon rearrangement reaction prior to the elimination of ethylene which is unlike to the behavior of α-tetralone.     

Bor-Stickstoff-Verbindungen. XXXIX. Untersuchungen über die Bildung von Borazolen: Zur Kenntnis der Reaktionsprodukte der Umsetzung von Bortrichlorid mit Methylamin

The reaction boron trichloride with methylamine can be directed to yield either tris(methylamino)borane or B-tris(methylamino)-N-trimethylborazine depending upon the molar ratio of the reactants. The vibrational spectrum of tris(methylamino)borane is discussed and the reaction of the compound with boron trichloride has been studied. Interpretation of the experimental data permits to suggest a possible mechanism for the formation of borazines.     

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°).     

Über die chemische Konstitution der mit Divinylsulfon vernetzten Cellulose. 12. Mitteilung über textilchemische Untersuchungen

Cotton and viscose fibres treated with divinyl sulphone under alkaline conditions were degraded in sulphuric acid. By column chromatography degradation products have been identified which contain two glucose units on mono- and dimeric sulphone derivatives, i.e. glucose ethers of 2,2′-dihydroxyethylsulphone and of 2,2′-bis-(hydroxyethylsulphonyl)-diethylether. This is the first direct chemical proof of the existence of cross-linkages in cellulose treated with bifunctional reagents.     

Tubotaiwin-N-oxid aus der Wurzelrinde von Conopharyngia johnstoni Stapf. 148. Mitteilung über Alkaloide

From the root bark of Conopharyngia johnstonii Stapf (Apocynaceae) the hitherto unknown tubotaiwine-N-oxide ( 2 ) together with tubotaiwine ( 1 ) were isolated and characterized.