Water reaction with diazonium

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. ... 

Complexation with crown ethers increases the notoriously low solubilities of diazonium salts in most solvents (with the obvious exception of water). Therefore, it is possible to carry out phase-transfer reactions with complexed diazonium ions (review Gokel et al., 1985). Useful examples can be found in a paper from Gokel s group (Beadle et al., 1984a) on the Gomberg-Bachmann and Pschorr reactions (see Sec. 10.10). 

As far as we are aware, the azo coupling of an ethyne derivative was only investigated over half a century ago Ainley and (Sir Robert) Robinson (1937) investigated the reaction of phenylethynes (phenylacetylenes) with diazonium ions (Scheme 12-59). Unsubstituted phenylethyne did not give identifiable products with the 4-nitrobenzenediazonium ion, but with the more nucleophilic 4-methoxyphenyl-ethyne an azo compound (12.119) was formed. On reaction with water it gives an arylhydrazone of an a-ketoaldehyde (12.120). 

The product should be used immediately because it deteriorates slowly at room temperature. It is freed of tetrahydrofuran by washing with the solvent to be used in subsequent reactions and transferred as a slurry in that solvent (cf. procedure B). Traces of water, if present, do not appear to interfere with subsequent reactions of diazonium carboxylates, as observed in the submitters laboratory. 

These X -phosphorins 720 a-c also fail to react with carbonyl compounds. However, they are attacked by electrophiles (H or alkyl cations) at the C—2 position. In this manner new 1,1-diphenyl-2,3-benzo-X-phosphorins which are sustituted at positions C—2 (and C-4) can be prepared. Diazonium ions attack at C—4 to form azocompounds if an excess is used, C—2 is also substituted Hydrolysis with hot water affords 747. The reaction with ortho-formic acid ester forms a cyanine dye having a bridge at the C—4 positions 142 The experimen-... 

The most satisfactory method of preparation of a copper(i) cyanide solution is to dissolve the copper(i) cyanide (90 g, 1 mol) in a solution of sodium cyanide (125 g, 2.5 mol) (CAUTION) in 600 ml of water. If it is desired to avoid the preparation of solid copper(i) cyanide, the following procedure may be adopted. Copper(i) chloride, prepared from 35 g of copper(n) sulphate pentahydrate as described under 22 above, is suspended in 60 ml of water contained in a 500-ml round-bottomed flask, which is fitted with a mechanical stirrer. A solution of 18.5 g of sodium cyanide (96-98%) in 30 ml of water is added and the mixture is stirred. The copper(i) chloride passes into solution with considerable evolution of heat. As the copper(i) cyanide is usually employed in reactions with solutions of aryl diazonium salts it is usual to cool the resulting copper(i) cyanide solution in ice. 

Actually, the reaction with alcohol may result in replacement of the —N2X group by —H or —OC2H5, and very often both types of products result. The most important factor in determining the course of the reaction is the nature of the substituents in the diazonium salt. The character of the products is also affected by the acid used for diazotiza-tion, the alcohol employed in the reduction, the presence of water and catalysts, and the reaction temperature. 

Bases, Neutral Salts.— As a base it forms salts, in which form the diazo compound is obtained by diazotization, and which though also unstable has been isolated in small quantities and the composition and properties determined. Of the three salts, the sulphate, chloride and nitrate, the first is the most stable and the last is the least stable. They are colorless crystalline neutral compounds soluble in water, difficultly soluble in alcohol and insoluble in ether. After being prepared by the ordinary diazo reaction, with sodium nitrite in cold acid water solution, they may be precipitated in crystalline form by the addition of alcohol and ether. If the diazotization is effected in alcohol solution by means of amyl nitrite or ethyl nitrite the crystals of the diazonium salt separate at once. These salts of diazo benzene all show true salt characteristics, e.g., they lower the freezing point of solutions. The diazo radical, (CeHs—N2—) is thus basic toward strong acids, and the hydroxide, the non-isolated hypothetical diazo benzene, CeHs—N2—OH, is the free base. It may be considered as the simplest aromatic diazo compound and the mother substance of all other members of the class. 

Reaction with Water Yields Phenols.—With water at ordinary or at raised temperatures diazonium salts readily decompose, the nitrogen is set free and the hydroxyl compound of the corresponding hydrocarbon is formed, i.e. the diazo group is entirely replaced by the hydroxyl group. Benzene diazonium chloride thus yields hydroxy benzene or phenol. 

Arenediazonium ion reactions often are complex.61 Benzenediazonium fluoro-borate in 2,2,2-trifluoro ethanol (TFE), for example, decomposes by first-order kinetics to give a mixture consisting largely of the ether (62%) formed by solvolysis and fluorobenzene (34%) resulting from reaction with fluoroborate ion. Addition of pyridine changes the kinetic order and gives rise to additional products.62 The same diazonium ion solvolyzes faster in TFE than in water. Because water is a better nucleophile than TFE, it is likely that a nucleophile is not involved in the rate limiting step of the reaction.63 ... 

Electrophilic substitution reactions at C-4 of phosphorins have been described. For example (104) reacts with diazonium salts in the presence of water (Scheme 7), to give an azo-compound, which can be protonated on the /S-nitrogen atom. In the presence of polarizable anions phosphinic acid derivatives (105) are formed. 

Two himdred grams of sodium nitrite is dissolved in 400 cc. of water in a 2-I. beaker, and 40 g. of copper powder is added (Note 3). The mixture is stirred with an efficient stirrer (Note 4), and a suspension of the -nitrophenyldiazonium fluo-borate in 200 cc. of water is added slowly. Much frothing occurs, and 4-5 cc. of ether is added from time to time to break the foam. The reaction is complete when all the diazonium compound has been added. The product is filtered with suction, washed several times with water, twice with dilute sodium hydroxide solution, and again with water. The solid is dried in an oven at 110°, powdered, and extracted with 300-cc., 200-cc., and 150-cc. 

The reaction of 2- and 6-amino groups with nitrous acid is similar to that of 2-amino-pyridines, in that diazonium salts are produced but, relative to phenyldiazonium salts, these are unstable. Despite this, they can be utilised for the introduction of groups such as halide or, oxygen by reaction with water, with loss of nitrogen. 8-Diazonium salts are considerably more stable. In 2-aminoadenosine, selective diazotisation occurs at the 2-amino group. ... 

Reaction of 1,2,4-triazinamines with nitrous acid yields, via the diazonium salts, cither the 1,2,4-triazinones by reaction with water or the chloro-l,2,4-triazines by reaction with chloride ions.350a,b... 

An amino group can also be acylated <84JHC697, 86JHC935) it reacts with sulfonyl chlorides and aryl isocyanates <86JHC935>, and also with nitrous acid to give, via the diazonium salt (281), either the triazinone by reaction with water or the chloro-triazine by reaction with chloride ions (Scheme 50). Nitrosation of 3-amino-1,2,4-triazine 2-oxides (282) and subsequent thermolysis of the diazonium tetrafluoroborate salts (283) afforded 3-fluoro-1,2,4-triazine 2-oxides (284) (Scheme 51). In one instance the diazonium tetrafluoroborate was isolated <85H(23)1969>. 

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