Nucleophile Substitutionen an Kohlensäurederivaten. XII. Kinetik und Mechanismus der Reaktion von N-Nitro-N-alkylurethanen mit primären aliphatischen Aminen

Nucleophilic Substitutions to Carbonic Acid Derivates. XII. Kinetics and Mechanism of the Reaction of N-Nitro-N-alkyl-urethanes with Primary Aliphatic Amines The aminolysis of N-alkyl-N-nitrourethanes takes place, as the kinetical studies demonstrate, by means of several consecutive steps. The nucleophilic attack of the amine (first step; reaction B), as well as the proton-transfere (second step; reaction C), are quick pre-equilibres, followed by the slow, rate-determining elimination of the nitramino-group (reaction D). During the deprotonation, an intermediate with two to the nitramino-group antiperiplanar orbitals is formed, providing the necessary mesomeric assistance of the elimination.     

Nucleophile Substitutionen an Kohlensäurederivaten. XIX. Alkoholyse und Hydrolyse des Bis(trichlormethyl)carbonates

Nucleophilic Substitutions at Carbonic Acid Derivatives. XIX. Alcoholysis and Hydrolysis of Bis(trichloromethyl)carbonate The rate constants of hydrolysis and alcoholysis of bis(trichlormethyl)carbonate in xan have been determinated conductometrically. The effects of the water and alcohol concentrations, the temperature and deuterium have been studied. By the hydrolysis and alcoholysis of bis(trichlormethyl)carbonate the nucleophilic attack of water and alcohol is the rate-determining step, followed by a fast elimination of unstable trichloro-methanol.     

Acylierung von Heterocyclen mit Kohlensäurederivaten. I. Kinetik und Mechanismus der Reaktion von 2-Aminobenzimidazolen mit Arylcyanaten

Acylation of Heterocycles with Carbonic Acid Derivatives. I. Kinetics and Mechanism of the Reaction of 2-Aminobenzimidazoles with Aryl Cyanates The second order rate constants for the reaction of 2-amino-benzimidazoles (2-ABI) with aryl cyanates forming 2-amino-benzimidazole aryl ester imide 3 have been determined in dependence on substituent effects by u. v. measurements. The results are interpreted by a six-membered cyclic transition state in which the electrophilic attack of the cyanate on the endocyclic N atom is catalyzed by an H bridge interaction of the exocyclic amino group of 2-ABI with the OCN group.     

Nucleophile Substitutionen an Kohlensäurederivaten. XX. Aminolyse des Bis(trichlormethyl)carbonates

Nucleophilic Substitutions at Carbonic Acid Derivatives. XX. Aminolysis of Bis(trichlormethyl)carbonate The rate constants for the two steps of the reaction of bis(trichlormethyl)carbonate with substituted anilines have been determinated by conductivity measurements. The first relatively fast step of the reaction is the nucleophilic attack of the amine to the bis(trichloromethyl)-carbonate leading to trichloromethylurethane through a six or four centers transition state in which the carbon-nitrogen bond is formed parallel with the transfer of the proton. In this reaction a phosgene molecule is also produced, which reacts very fast with amine to form a N,N′-diarylurea. The second, much slower step, is the nucleophilic attack of the amine to the trichloromethylurethane. Through a similar transition state in which the proton transfer has even a higher importance, a N,N′-disubstituted urea and an other molecule of phosgene are formed.     

Acylierung von Heterocyclen mit Kohlensäurederivaten. IV. Umsetzung von Benzoxazolin 2-thion mit Arylcyanaten. Kinetik und Mechanismus

Acylation of Heterocycles with Carbonic Acid Derivatives. IV. Reaction of Benzoxazolin-2-thione with Aryl Cyanates. Kinetics and Mechanism The arylcyanate benzoxazoline-2-thione ( 1 ) reaction in the presence and absence of the tertiary amines yields 1-aryloxyiminocarbonylbenzoxazoline-2-thione ( 2 ) and 2-thiocyanatobenzoxazole (4). A mechanism is proposed based on the influences of the reactants concentration, the concentration and basicity of tertiary amines, the solvent-water concentration, the arylcyanate substituents electronic effects on the reaction rate and the apparent activation parameters. This mechanism consists in the nucleophilic attack of the benzoxazoline-2-thione S-atom on the cyanate, followed by rearrangement through a four-center transition state.     

Nucleophile Substitution in der 1,3,5-Triazinreihe. IX. Kinetik und Mechanismus der Reaktion von Cyanurchlorid mit 4′-substituierten 4-Aminoazobenzenen

Nucleophilic Substitutions in 1,3,5-Triazines. VII. The Kinetic and ¦ Mechanism of Cyanuric Chloride with 4′-Substituted 4-Aminoazobenzens The kinetic and mechanism of cyanuric chloride reaction with 4′-substituted 4-aminoazobenzens in dioxan-water was studied by conductometry. An addition-elimination mechanism with a monomolecular elimination of chlorine ion at low water concentrations or a nucleophilic attack of 4-aminoazobenzens at high water concentration as low step has been supported by experimental data.     

Acylierung von Heterocyclen mit Kohlensäurederivaten. II. Endo- und exo-Carbamoylierung von 2-Amino-benzimidazol-Derivaten mit Isocyanaten. Mechanismus der Acylgruppenwanderung

Acylation of Heterocycles with Carbonic Acid Derivatives. II. Endo and Exo Carbamoylation of 2-Amino-benzimidazole Derivatives with Isocyanates. Mechanism of the Acyl Group Migration 2-Amino-benzimidazoles react with isocyanates with good yields to give 2-amino-1-carbamoyl-aminobenzimidazoles 1 at −30°C and the corresponding 2-carbamoyl isomeres 2 at room temperature, respectively. The isomerization mechanism was studied by crossover experiments and kinetic measurements and has been found to consist of inter- and monomolecular acyl transfer.     

Struktur und Reaktivität heterosubstituierter Nitrile. XVI[1]. Kinetik und Mechanismus der Arylcyanatbildung aus Bromcyan und Phenolen

Structure and Reactivity of Heterosubstituted Nitriles. XVI. Kinetics and Mechanism of the Formation of Arylcyanates from Cyanogen Bromide and Phenoles The first-order and second-order rate constants of the reaction of cyanogen bromide with phenoles in the presence of tertiary aliphatic amines were determined in absolute acetone. The first step of the reaction is the nucleophilic attack of the tertiary amine at the cyanogen bromide. By a fast equilibrium reaction an N-cyano-N,N,N-trialkylammonium bromide is formed, which is attacked by the phenol as a nucleophile or dissociates in the slowest steps of the reaction. The nucleophilicity and the steric hinderance of the tertiary amine, and the nucleophilicity of the phenole as well determine, which of these reactions is favoured.     

Nucleophile Substitutionen an Bischlornitrosoverbindungen. III. Reaktionen mit Salzen und Estern der Dithiocarbazinsäure sowie der N-Phenyldithiocarbazinsäure

Nucleophilic Substitutions with Bischloronitroso Compounds. III. Reactions with Salts and Esters of the Dithiocarbazinic Acid and the N-Phenyldithiocarbazinic Acid Bischloronitroso compounds 1 react with salts of the dithiocarbazinic acid to give S-(β-oximinoalkyl)-esters of the dithiocarbazinic acid. The esters easily cyclise to the corresponding 1,3,4-thiadiazine-2-thiones. Esters of the dithiocarbazinic acid lead to 2-alkylthio-1,3,4-thiadiazines. The structure of possible tautomeres follows from i.r.-, u.v./vis- and n.m.r.-spectra.     

Phosphororganische Antioxidantien. II. Kinetik und Mechanismus der Zersetzung von Alkylhydroperoxiden durch Esteramide der phosphorigen- und Phosphorsäure

Organophosphorus Antioxidants. II. Kinetics and Mechanism of the Decomposition of Alkylhydroperoxides by Esteramides of Phosphorous and Phosphoric Acid The reaction mechanism of 2-amido-1,3,2-benzodioxaphospholes ( 1 ) with cumyl and t-butylhydroperoxide has been studied kinetically by means of ³¹P-n.m.r. and e.p.r. spectroscopy and high pressure liquid chromatography. 1 reacts with cumyl hydroperoxide to give the corresponding 2-oxides ( 2 ) which with more hydroperoxide and/or water form the phosphate esters 7 and 8 . These acidic phosphates decompose cumyl hydroperoxide catalytically giving phenol and acetone. All amides ( 1 ) react with t-butyl hydroperoxide stoichiometrically to give t-butanol. The ionic mechanism of hydroperoxide decomposition is accompanied in a minor proportion by a homolytical one.     

Struktur und Reaktivität heterosubstituierter Nitrile. 24 Kinetik und Mechanismus der Reaktion von o-Phenylendiamin mit Arylcyanaten

Structure and Reactivity of Heterosubstituted Nitriles. 24. Kinetics and Mechanism of the Reaction of o-Phenylen diamine with Aryl Cyanates The second and third order rate constants for the reaction of o-phenylene diamine with aryl cyanates to 2-amino benzimidazole phenylester imide in water/dioxane have been determined by i.r. measurements. The reaction proceeds through a bimolecular and a trimolecular mechanism simultaneously. In the slow step of the bimolecular process an electrophilic attack of the aryl cyanate on o-phenylene diamine takes place in a seven membered cyclic transition state. The slow step of the trimolecular mechanism consists of a nucleophilic attack of the diamine on a phenole aryl cyanate associate by a six membered cyclic transition state. The final products of both reactions are formed by successive fast reactions.     

Nucleophile Substitutionen in der 1, 3, 5-Triazinreihe. VIII. Zur Hydrolyse des Cyanurchlorids in Dioxan-Wasser

Nucleophilic Substitutions in the 1, 3, 5-Triazines. VIII. The Hydrolysis of Cyanuric Chloride in Dioxane Water The kinetics of cyanuric chloride first step hydrolysis in dioxan-water was conductometrically studied. At small water concentrations the slow stage of hydrolysis at 2,4-dichloro-6-hydroxy-1,3,5-triazin consists in the nucleophilic attack ot water molecule to cyanuric cloride. At higher water concentrations the rate of this process exceeds that of the chlorine anion monomolecular elimination which becomes the slow step.     

Phosphororganische Antioxidantien. I. Kinetik und Mechanismus der Zersetzung von Alkyl-hydroperoxiden durch o-Phenylen-phosphite und -phosphate

Organophosphorus Antioxidants. I. Kinetics and Mechanism of the Decomposition of Alkylhydroperoxides by o-Phenylene Phosphites and Phosphates The reaction mechanism of 2-(2, 6-di-tert-butyl-4-methyl-phenoxyl)-1,3,2-benzodioxaphosphole ( 1 ) with cumyl and t-butyl hydroperoxide has been studied kinetically by means of ³¹P-n.m.r. spectroscopy and high pressure liquid chromatography. 1 reacts with cumyl hydroperoxide to give the corresponding 2-oxide ( 2 ) which with more hydroperoxide and/or water forms the open chained phosphate ester 5 . This acidic phosphate decomposes hydroperoxide catalytically. The kinetic parameters of the separate reaction steps are given. The ionic mechanism of hydroperoxide decomposition is accompanied by a homolytic one in a minor proportion.