Mastering Chemistry Help

Replacement reaction of benzene diazonium chloride by halide ion When the solution of freshly prepared benzene diazonium salt is trated with a mixture of cuprous chloride or cuprous bromide in presence of concentrated HCL or HBr, we get chlorobenzene or bromobenzene. This reaction is known as Sandmaeyer's reaction . Alternatively the same reaction can be done by copper powder and cone. HX instead of cuprous halide and this modified reaction is called Gatterman reaction . Indobenzene can be prepared from benzene diazonium salt by reacting with KI solution. Replacement with fluoride is known as Balz Schiemann reaction .In this benzene diazonium salt is reacted with fluoroboric acid heated to get fluorobenzene . Preparation of aryl halides from diazonium salt by replacement gives pure aryl halides and provides important synthetic route for preparation of aryl iodides and aryl fluorides. Visit http://www.entrancechemistry.blogspot.in/2013/05/reactions-of-ben...

 Chemical reactions of benzene diazonium chloride Due to unstable nature diazonium group ( -N 2 - X + ) is a good leaving group. In most of the reactions of diazonium salt, -N 2 - X +   group is replaced by other groups. Such reactions are usually grouped under replacement reactions. I n the second type, due to electron deficiency (+ve charge) on diazonium ion, it can behave like an electrophile and couple with electron rich aromatic compounds and undergo coupling reactions. Replacement reactions of benzene diazonium chloride Depending on replacing groups these reactions can be mentioned under following heads. In this way we can easily introduce_F, -CI, -I, -OH and -CN groups in the aromatic ring. 1. Replacement by halide ion ( Sandmaeyer's reaction ) 2. Replacement by cyanide ion 3. Replacement with OH - ion 4. Replacement with hydrogen

Diazonium salt reactions Diazonium salts have N2 X functional group attached to an aryl group. They are highly unstable and are mainly used as a synthetic intermediate for various compounds. Alkyl diazonium salt do not exist even below 00C.   Nomenclature of Diazonium salt   The name is obtained by adding diazonium chloride, sulphate etc. to the name of parent hydrocarbon. Methods of Preparation Aromatic diazonium salts are prepared from aromatic primary amines. aromatic primary amine is taken in the ice-cold solution of HCL and adding sodium nitrite at 00C we get aromatic diazonium salt. This reaction is known as diazotisation. Diazonium salt are highly unstable and they are not stored and they are not stored and are used immediately after their preparation.

Cyanides are the compounds with functional group -CN and can be regarded as the derivatives of hydrogen cyanide (HCN). The cyanide group is an ambident group. This means cyanide group can attach to alkyl or aryl group through both carbon atoms as well as nitrogen atom. Thus the compounds obtained by replacement of the H-atom of hydrogen cyanides by alkyl or aryl group are called organic cyanides or nitriles. Isocyanides are the compounds isomeric with cyanides and can be regarded as derived from Hydrogen isocyanide by replacement of H by alkyl or aryl group.

Reaction of nitrous acid with Aromatic Primary amines At 273 - 278 K, atomic primary amines react with sodium nitrite and dilute HCl, to give aromatic diazonium salts. For example, aniline forms benzene diazonium chloride. Aromatic diazonium salts are stable only at low temperature. Hence at higher temperature, aromatic primary amine gives phenols. Reaction of nitrous acid with Aromatic Primary amine Aliphatic diazonium salts are highly unstable and hence alcohols are obtained when aliphatic primary amines are reacted with nitrous acid.

Chemical properties of amines In most of its reaction, amines act as a nucleophile or a base due to lone pair on nitrogen. In aromatic amines, due to resonance, the -NH 2 group make the ring more susceptible to electrophilic substitution at ortho and para position. Important reactions of amines are classified as :   1. Salt formation Amines are soluble in mineral acids and carboxylic acids, due to the formation of soluble ammonium salts. RNH 2 + HCl  ------->  RNH 3 + Cl - C 6 H 5 NH 2 --------> C 6 H 5 NH 3 + Cl - 2. Alkylation Alkyl halides when react with primary or secondary amines undergo nucleophilic substitution. When HX is removed, secondary or tertiary amine formed will again reacts with alkyl halide froming tertiary amine and finally quaternary ammonium salt.   3. Acylation 4. Reaction with carbonyl compounds 5. Carbylamine reaction 6. Reaction with nitrous acids With nitrous  acid primary, secondary and ter...