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The phenol formed may react with the diazonium salt and hence the reaction is carried in the presence of an acid which suppresses this further reaction. [33] A Sandmeyer-type hydroxylation is also possible using Cu 2 O and Cu 2+ in water.
Azo printing exploits this reaction as well. In this case, the diazonium ion is degraded by light, leaving a latent image in undegraded diazonium salt which is made to react with a phenol, producing a colored image: the blueprint. [3] Prontosil, the first sulfa drug, was once produced by azo coupling. The azo compound is a prodrug that is ...
More recently, trifluoromethylation of diazonium salts has been developed and is referred to as a 'Sandmeyer-type' reaction. Diazonium salts also react with boronates, iodide, thiols, water, hypophosphorous acid and others, [6] and fluorination can be carried out using tetrafluoroborate anions (Balz–Schiemann reaction). However, since these ...
The tetrafluoroborate can be obtained from crude benzenediazonium chloride by salt metathesis using tetrafluoroboric acid. [C 6 H 5 N 2]Cl + HBF 4 → [C 6 H 5 N 2]BF 4 + HCl. The tetrafluoroborate is more stable than the chloride. [2]
Oxidative coupling of phenol by VCl 4. Coproducts including vanadium(III) and hydrogen chloride are not shown. Oxidative phenol couplings can occur through either inner sphere or outer sphere processes. In inner sphere processes, the phenolic substrate coordinates to the metal center to give a phenoxide complex.
Phenol esters are active esters, being prone to hydrolysis. Phenols are reactive species toward oxidation. Oxidative cleavage, for instance cleavage of 1,2-dihydroxybenzene to the monomethylester of 2,4 hexadienedioic acid with oxygen, copper chloride in pyridine [4] Oxidative de-aromatization to quinones also known as the Teuber reaction.
[8] [9] The diazotization reaction can be effected with nitrosonium salts such as [NO]SbF 6 without isolation of the diazonium intermediate. [2] As a practical matter, the traditional Balz–Schiemann reaction consumes relatively expensive BF 4-as a source of fluoride. An alternative methodology produces the fluoride salt of the diazonium compound.
Phenylhydrazine is prepared by reacting aniline with sodium nitrite in the presence of hydrogen chloride to form the diazonium salt, which is subsequently reduced using sodium sulfite in the presence of sodium hydroxide to form the final product. [6]