Diazonium salts, aryl

Unsymmetrical diaryls may be prepared by treating an aryl diazonium salt solution with sodium hydroxide or sodium acetate in the presence of a liquid aromatic compound. Thus 2-chlorodiphenyl is readily formed from o-chloro phenyl diazonium chloride and sodium hydroxide solution (or sodium acetate solution) in the presence of benzene ... 

Primary arylamines like primary alkylammes form diazonium ion salts on nitro sation Aryl diazonium 10ns are considerably more stable than their alkyl counterparts Whereas alkyl diazonium 10ns decompose under the conditions of their formation aryl diazonium salts are stable enough to be stored m aqueous solution at 0-5°C for a rea sonable time Loss of nitrogen from an aryl diazonium ion generates an unstable aryl cation and is much slower than loss of nitrogen from an alkyl diazonium ion... 

The reaction of an aryl diazonium salt with potassium iodide is the standard method for the preparation of aryl iodides The diazonium salt is prepared from a primary aro matic amine m the usual way a solution of potassium iodide is then added and the reac tion mixture is brought to room temperature or heated to accelerate the reaction... 

Sodium borohydride has also been used to reduce aryl diazonium salts m reductive deam mation reactions... 

A reaction of aryl diazonium salts that does not involve loss of nitrogen takes place when they react with phenols and arylamines Aryl diazonium ions are relatively weak elec trophiles but have sufficient reactivity to attack strongly activated aromatic rings The reaction is known as azo coupling two aryl groups are joined together by an azo (—N=N—) function... 

Nitrosation (Section 22 15) Nitrosation of amines occurs when sodium nitrite is added to a solution containing an amine and an acid Primary amines y e d alkyl diazonium salts Alkyl diazonium salts are very unstable and yield carbo cation derived products Aryl diazonium salts are exceedingly useful synthetic in termediates Their reactions are de scribed in Table 22 7... 

Preparation of aryl iodides Aryl diazonium salts react with sodium or potassium iodide to form aryl iodides This is the most general method for the synthesis of aryl iodides... 

Reaction of aryl diazonium salts with iodide ion (Section 22 17) Adding po tassium iodide to a solution of an aryl diazonium ion leads to the formation of an aryl iodide... 

Azo coupling (Section 22 18) Formation of a compound of the type ArN=NAr by reaction of an aryl diazonium salt with an arene The arene must be strongly activated toward... 

Two mechanisms are among those that have been postulated for decomposition of aryl diazonium salts in aqueous solution containing nucleophilic anions, A ... 

Preparation of aryl nitriles Cop-per(l) cyanide converts aryl diazonium salts to aryl nitriles. 

In a basic medium, 5-nitro-5-hydroxymethyltetrahydro-l,3-oxazine derivatives can be coupled with aryl diazonium salts to form aryl-azo derivatives (54) with the elimination of a molecule of formaldehyde. ... 

Incidentally, 31 contributes more to the hybrid than 32, as shown by bond-distance measurements. In benzenediazonium chloride, the C—N distance is 1.42 A, and the N—N distance 1.08 A, which values lit more closely to a single and a triple bond than to two double bonds (see Table 1.5). Even aromatic diazonium salts are stable only at low temperatures, usually only below 5°C, though more stable ones, such as the diazonium salt obtained from sulfanilic acid, are stable up to 10 or 15°C. Diazonium salts are usually prepared in aqueous solution and used without isolation, though it is possible to prepare solid diazonium salts if desired (see 13-20). The stability of aryl diazonium salts can be increased by crown ether complexion. ... 

It is noted that the reaction of aryl diazonium salts with CuCN to give benzonitrile derivatives is also called the Sandmeyer reaction. It is usually conducted in neutral solution to avoid liberation of HCN. 

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