diazonium salts have the general formula R N X where R stands for an aryl group and X ion may be Cl – Br, HSO , BF , etc. They are named by suffixing diazonium to the name of the parent hydrocarbon from which they are formed, followed by the name of anion such as chloride, hydrogensulphate, etc. The group is called diazonium group. For example, Cl is named as benzenediazonium chloride and C H N + HSO – is known as benzenediazonium hydrogensulphate.
Primary aliphatic amines form highly unstable alkyldiazonium salts (refer to Section . ). Primary aromatic amines form arenediazonium salts which are stable for a short time in solution at low temperatures ( - K). The stability of arenediazonium ion is explained on the basis of resonance.
Benzenediazonium chloride is prepared by the reaction of aniline with nitrous acid at -278K. Nitrous acid is produced in the reaction mixture by the reaction of sodium nitrite with hydrochloric acid. The conversion of primary aromatic amines into diazonium salts is known as diazotisation . Due to its instability, the diazonium salt is not generally stored and is used immediately after its preparation.
278K NaNO 2H Na Cl Cl Cl H 2H . Arrange the following in increasing order of their basic strength: (i) C H NH , C H NH , NH , C H CH NH and (C H ) NH (ii) C H NH , (C H ) NH, (C H ) N, C H NH (iii) CH NH , (CH ) NH, (CH ) N, C H NH , C H CH NH . . Complete the following acid-base reactions and name the products: (i) CH CH CH NH + HCl ® (ii) (C H ) N + HCl ® .