35815-41-9

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• 98-09-9 benzenesulfonyl chloride 
• 1689-82-3 4-hydroxyazobenzene 

Relevant academic research and scientific papers

NUCLEOPHILIC MECHANISM OF CATALYSIS. COMPARATIVE REACTIVITY OF 4-DIMETHYLAMINOPYRIDINE AND ITS N-OXIDE IN THE PHENOLYSIS OF ARENESULFONIC ACID DERIVATIVES IN METHYLENE CHLORIDE

The catalysis of the reaction of benzenesulfonyl chloride with 4-phenylazophenol by 4-dimethylaminopyridine N-oxide in methylene chloride at 25 deg C was studied under conditions with the accumulation of the nucleophilic catalysis intermediate N-phenylsulfonyloxypyridinium chloride.It was shown that the reaction of the intermediate with 4-phenylazophenol (the rate-controlling stage) takes place with general base assistance from the free N-oxide.On the basis of these and previously obtained data it was concluded that the nucleophilic catalysis of the phenolysis processes is realized exclusively in conjunction with general-base catalysis.In the analogous arylaminolysis processes the general-base assistance is substantially smaller.The most effective catalyst for the formation of arylamides and aryl ethers in a proton inert medium are proposed.

KINETICS OF THE PHENOLYSIS OF ACID CHLORIDES IN A PROTON-INERT MEDIUM. NUCLEOPHILIC CATALYSIS BY TERTIARY AMINES

The kinetics of the reactions of ArOH with acid chlorides (AcX), catalyzed by tertiary amines (B), were studied by UV spectroscopy in methylene chloride (25 deg C): 1) Benzoyl chloride with β-naphthol (B = N-methylimidazole); 2) benzenesulfonyl chloride with p-phenylazophenol (B = 4-dimethylaminopyridine) with the following concentrations 0 >/= 0 >> 0.A nucleophilic mechanism of catalysis with rapid and equilibrium accumulation of the intermediate products, i.e., N-benzoyl-3-methylaminoimidazolium (Ia) and N-phenylsulfonyl-4-dimethylaminopyridinium (Ib) chlorides, is realized in the case of reactions (1) and (2).In the slow stage the intermediates (I) transfer the acyl group not to the free ArOH but to the hydrogen-bonded complexes of ArOH with (I) and with the amines (B), the formation constants of which were determined independently.One of the above-mentioned paths represents the "intramolecular" transfer of the acyl group in the associate ArOH...(I), whereas the second represents bimolecular attack by the intermediate (I) on the complex ArOH...B.In view of the complexing effects an equation was derived for the phenolysis rate which makes it possible to calculate the rate constants for transfer of the acyl group.Thus, the motivating force of the reactions (1) and (2) in the proton-inert medium is proton transfer even in the initial state, while nucleophilic catalysis is realized exclusively in conjunction with general-base assistance on the part of the anion of the intermediate (I) ("intramolecular" catalysis) or on the part of the free base B (intermolecular catalysis) to the transfer of the proton from ArOH in the rate-controlling stage.

KINETICS AND MECHANISM OF THE PHENOLYSIS OF ARENESULFONIC ACID DERIVATIVES IN THE PRESENCE OF 4-(DIMETHYLAMINO)PYRIDINE IN METHYLENE CHLORIDE

The kinetics of the phenolysis of benzenesulfonic acid derivatives C6H5SO2X (X=Cl, Br, C6H5SO3), catalyzed by 4-(dimethylamino)pyridine in methylene chloride at 25 deg C, were studied by UV spectroscopy.A comparative analysis was made of the kinetic relationships governing the phenolysis and aminolysis of benzenesulfonyl-4-(dimethylamino)pyridinium salts in terms of a nucleophilic mechanism of catalysis.From analysis of these relationships it follows that the fundamental difference between the kinetics of aminolysis and phenolysis lies in the fact that in the first case the hydrogen-bonded intermediate complex of the benzenesulfonylpyridinium salt with the amine is the leading particle in several kinetically independent paths, whereas the analogous complex with the phenol is a nonreactive particle.