Diazo group, chlorine replacement

The diazonium salts usually decompose when warmed with water to give a phenol and nitrogen. When treated with CuCl, CuBr, KI, the diazo group is replaced by chlorine, bromine or iodine respectively (Sandmeyer reaction). A diazonium sulphate and hydroxyl-amine give an azoimide. The diazonium salt of anthranilic acid (2-aminobenzoic acid) decomposes to give benzyne. ... 

The use of copper salts and of copper itself for the replacement of the diazo-group of aromatic compounds, by chlorine, bromine, cyanogen, otc., is important. 

It has been demonstrated that the presence of chlorine or bromine in the nucleus facilitates replacement of the diazo group by hydrogen little or no ether formation occurs.26 Apparently iodine also favors the redudng action of alcohols, but this point has not been investigated carefully.26 27 No attempts to deaminate fluorinated amines are recorded. Representative of the effitiency with which ethanol reduces diazonium salts derived from halogenated amines are the deaminations of m-chloroaniline 26 (87% yield), of 2-bromo-4-methylaniline 28 (67% yield), of 2,4,6-tribfomoaniline 29 (ca. 80% yield), and of 2-carboxy-4-iodoaniline30 (ca. 45% yield) in the biphenyl series the deamination of VIII in 53% yield 31 may be dted. 

The diazo group can be replaced with chlorine or bromine by reaction with cuprous chloride or cuprous bromide. [The Cu(l) aids in the formation of the radicals that are involved in these particular reactions.]... 

Diazotization of aminophenothiazines yields the expected results only when there is stabilization of the amino groups by suitable ring substituents. 3-Amino-lO-methylphenothiazine and 3-amino-lO-ethylphenothiazine-5,5-dioxide have been diazotized and coupled with hydroxy- and aminonaphthalenes. Diazo groups have only been successfully replaced by hydrogen and chlorine. Thus, Flory... 

The present experiment illustrates the replacement of the diazo group by iodine, and Experiment 55 the use of cuprous halides in the replacement of the diazo group by chlorine. 

Introduction. In the preceding experiment it was shown that an aqueous solution of a diazonium salt treated with a solution of an alkali iodide gives iodobenzene. The replacement of the diazo group, N2X, by chlorine or bromine atoms involves the catalytic action of copper salts. Thus, benzenediazonium chloride warmed with a solution of cuprous chloride and hydrochloric acid gives chlorobenzene with cuprous bromide, bromobenzene is formed. The use of the cuprous salt is known as the Sandmeyer method. Instead of cuprous salts, finely divided copper may be used according to Gatterman s method. 

REACTION REPLACEMENT OF A DIAZO-GROUP BY CHLORINE, BROMINE, OR CYANOGEN... 

The diazo-group cannot be replaced in the same way by iodine as by chlorine, bromine or cyanogen. If a water solution of a diazochloride, -bromide, or -cyanide is heated, a phenol is formed, as is also the case on heating a diazo-sulphate. -... 

The Sandmeyer reaction involves the replacement of the diazo group by a halogen, usually chlorine or bromine, using copper(I) halides (Figure 13.5). The reaction with CuCN, noted previously, may have the same mechanism (yide infra). 

The determination of the amino group is often conveniently accomplished by converting it into the diazoderivative and replacing the nitrogen by chlorine as a rule the diazo-compound is not isolated. The following examplewill serve to illustrate the method ... 

Preparation by diazotization of 3-amino-2-hydroxy-6-methoxyacetophenone with sodium nitrite in dilute sulfuric acid at 0°, and replacement of the diazo-nium group by chlorine with a solution of cuprous chloride in 2 N hydrochloric acid at 100° (Sandmeyer reaction) (37%) [1884]. 

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