Alkyl diazonium salt

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... 

Alkyl diazonium salts can lose nitrogen to give 1°, 2°, or 3° carbocations, depending on the nature of the alkyl group. 

Alkyl diazonium salts are generally not useful compounds. They readily decompose below room temperature to form carbocations with loss of N2, a very good leaving group. These car-bocations usually form a complex mixture of substitution, elimination, and rearrangement products. 

Propose a reason why aryl diazonium salts are more stable than alkyl diazonium salts. 

Alkyl diazonium salts are unstable even at low temperature. They decompose to form carbocations, which go on to form products of substitution, elimination, and (sometimes) rearrangement. Keeping this in mind, draw a stepwise mechanism that forms all of the following products. 

You met diazoniumsa Xs in Chapter 23. Arene diazonium salts are stable compounds, but alkyl diazonium salts, which are formed by protonation of diazo compounds, are not. They decompose rapidlyto carbocations— thiswas how the carboxylic acid got methylated at the beginning of... 

In this process, 3° alcohols react faster than 2° alcohols. Heterolytic bond cleavage of a halide or sulfonate ester (C-X, X = Br, Cl, I, OMs, OTs, etc.) in aqueous solvents (usually with heating) generates tertiary cations easily, secondary alcohols with difficulty, and primary cations with extreme difficulty. Reaction of aldehydes and ketones with an acid catalyst gives the oxygen-stabilized cation (see 1 and 4). Reaction of amines with nitrous acid (HNO2) initially gives a diazonium salt (5, also see sec. 13.9.B) but alkyl diazonium salts readily decompose to cations. ... 

While the alkyl diazonium salt is unstable and loses nitrogen to form a variety of alkenes and alcohols, the aryl type is stable and has synthetic importance. When an aniline such as p-toluidine is converted to its diazonium salt, the temperature is kept low to avoid formation of the phenol. 

Primary oBcyl amines will give alkyl diazonium salts, and primary aryl amines will give aryl diazonium salts ... 

Alkyl diazonium salts are not terribly useful. They are very explosive, and as a result, they are very dangerous to prepare. But aryl diazonium salts are much more stable, and they are incredibly useful, as we will see in the upcoming section. For now, let s just make sure that we know how to... 

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