Compounds aromatic diazonium

Quaternary ammonium compounds are important in biological processes. One of the most common natural quaternary ammonium ions is choline, which is present in phospholipids (Sec. 15.6). 

Choline is not only involved in various metabolic processes, but is also the precursor of acetylcholine (page 327), a compound that plays a key role in the transmission of nerve impulses. The mushroom Amanita muscaria contains the deadly neurotoxin muscarine, which structurally resembles acetylcholine and probably interferes with the function of this neurotransmitter. 

Primary aromatic amines react with nitrous acid at 0 C to yield aryldiazonium ions. In diazotization, primary aromatic The process is called diazotization. amines react with nitrous acid to 

Diazonium compounds are extremely useful synthetic intermediates. Before we describe their chemistry, let us try to understand the steps in eq. 11.27. First, we need to examine the structure of nitrous acid. 

Nitrous acid decomposes rather rapidly at room temperature. It is therefore prepared as needed by treating an aqueous solution of sodium nitrite with a strong acid at ice temperature. At that temperature, nitrous acid solutions are reasonably stable. 

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The conversion of an aromatic diazonium compound into the corresponding arsonic acid by treatment with sodium arsenite in the presence of a catalyst, such as copper or a copper salt, is called the Bart reaction. A modification of the reaction employs the more stable diazonium fluoborate in place of the diazonium chlorid.i. This is illustrated by the preparation of />-nitrophenylarsonic acid ... 

Aromatic diazonium compounds became industrially very important after Griess (1866a) discovered in 1861/62 the azo coupling reaction, by which the first azo dye was made by C. A. Martius in 1865 (see review by Smith, 1907). This is still the most important industrial reaction of diazo compounds. Hantzsch and Traumann (1888) discovered that a heteroaromatic amine, namely 2-aminothiazole, can also be diazotized. Heteroaromatic diazonium compounds were, however, only used for azo dyes much later, to a small extent in the 1930 s, but intensively since the 1950 s (see Zollinger, 1991, Ch. 7). 

In aromatic diazonium compounds containing an ionized hydroxyl group ( —O-) in the 2- or 4-position, it is necessary to consider delocalization of electrons and, therefore, two mesomeric structures (1.7a-1.7b) (see Sec. 4.2). This fact has implications for nomenclature compounds of this type are considered as quinone derivatives following IUPAC Rule C-815.3 (Exception) compounds of this class are called quinone diazides. As a specific compound 1.7a-1.7b is indexed in Chemical Abstracts as 4-diazo-2,5-cyclohexadien-l-one. If reference is made specifically to mesomeric structure 1.7b, however, it is called 4-diazoniophenolate. 

More abundant are reductions with sodium sulfite which is applied in aqueous solutions (solubility 24%). Its specialties are reduction of peroxides to alcohols [257], of sulfonyl chlorides to sulfinic acids [252], of aromatic diazonium compounds to hydrazines [253], and partial reduction of geminal polyhalides [254] Procedure 43, p. 216). 

Aromatic diazonium compounds which are prepared readily by diazotization of primary amines can be converted either to their parent compounds by replacement of the diazonium group with hydrogen, or to hydrazines by reduction of the diazonium group. Both reactions are carried out at room temperature or below using reagents soluble in aqueous solutions, and usually give high yields. 

Reaction XLIX. (a) Action of Cuprous Potassium Cyanide on Aromatic Diazonium Compounds. (Sandmeyer). (B., 17, 1633, 2650 18, 1492, 1496.)—If a diazonium salt is added to a hot solution of cuprous-potassium cyanide, and the whole boiled on a water hath, nitrogen is evolved, and the corresponding nitrile formed. (C. r., 183, 421.)... 

Reaction XLIX. (b) Action of finely divided Copper and Alkali Cyanides on Aromatic Diazonium Compounds (Gattermann). (B., 23, 1218.)—This is the Gattermann modification of the preceding Sandmeyer reaction as usual, the cuprous salt is replaced by finely divided copper. This method gives better yields of some aromatic nitriles. 

Heterocycles as Coupling Components. If heterocyclic polyamine coupling components, e g., 2,4-diamino-6-hydroxypyrimidine, are used as coupling components with aromatic diazonium compounds, dyes are obtained that color polyacrylonitrile in lightfast yellow shades and are characterized by excellent leveling properties [5], An example is 1 [6979-64-2],... 

Coupling of Aromatic Diazonium Compounds with Phenols and... 

Methyl-, benzyl- and toluene-sulphonamide react with aromatic diazonium compounds to give isolable triazenes which decompose in the presence of alkali with the formation of the corresponding aromatic azide and the alkyl- or aryl-sulphinic acid salt . This sequence (equation 123), known as the Dutt-Wormall reaction, is mechanisti-... 

Bart reaction. (Scheller modification Star-key modification). Formation of aromatic arsonic acids by treating aromatic diazonium compounds with alkali arsenites in the presence of cupric salts or powdered silver or copper in the Scheller modification, primary aromatic amines are diazotized in the presence of arsenious chloride and a trace of cuprous chloride. 

A generally applicable procedure for conversion of aromatic amines into phenols or naphthols consists of boiling aromatic diazonium compounds (for their preparation see page 581). This method will be illustrated here by some examples. 

Two monographs deal in detail with the preparation, properties, reactions, and constitution of aromatic diazonium compounds.2494 The diazotization of proteins has been described by Rohrlich.261... 

Open-chain diazo-a,a -dicarbonyl compounds form complexes with boron trifluoride. There are two types of such complexes, as shown by Fahr and Hormann (1965) by means of IR spectra. In the solid state, the complexes show similarities to aromatic diazonium compounds, they have a quasi-aromatic six-membered chelate ring (2.35). They also undergo a reaction typical of solid aromatic diazonium salts, namely the Balz-Schiemann reaction (see Zollinger, 1994, Sect. 10.4), in which the corresponding fluoro-a,ct -dicarbonyl compound 2.36 is formed (2-12) (Prim and Schank, 1978). In benzene solution, however, the 1 2 complex is not chelated, rather Fahr and Hermann s IR data indicate structure 2.37. 

This reaction was first reported by Bart in 1910. It is the synthesis of arylarsenic acids from aromatic diazonium compounds with alkali arsenites in the presence of cupric salts, powdered silver, or copper. Therefore, this reaction is generally known as the Bart reaction. In addition, the reaction between aromatic diazonium and arsenious chloride in the presence of trace amounts of cuprous chloride is referred to as the Scheller modification. Besides the Scheller modification, the Sakellarios modification is the reaction between sulfanilamide and phenyldisodium arenite. ... 

Schlesinger reported cation photopolymerization of the oligomer with an epoxy ring. Cation polymerization does not give any effect of oxygen inhibition. An aromatic diazonium compound was used for the initiator-generated Lewis acid by irradiation. 

Reaction of cyanide with aromatic diazonium compounds (Section 23.8E). 

M. Aromatic Diazonium Compounds Rearrangements of Quaternary Compounds... 

Many fluoroborate salts of aromatic diazonium compounds have a high degree of stability. 

If we had done this reaction with an aliphatic compound, for example, cyclohexylamine, we would still make the diazonium salt, but aliphatic diazonium salts are much less stable than aromatic ones, and this would decompose with loss of molecular nitrogen at -50 °C. Aromatic diazonium compounds are more stable, because the aryl cation that would be produced by nitrogen loss is at an sp carbon atom, which, as we noted in Chapter 11, is very unfavorable. However, molecular nitrogen is a fabulous leaving group the N=N triple bond has lots of enthalpy, and the process also benefits from the entropy of the loss of a mole of gas. So the diazonium salt decomposes slowly to give an aromatic cation, which is then captured by any available nucleophile (Figure 13.2). 

If the diazonium compound is struck by light, it will form a non-reactive product. If an unexposed aromatic diazonium compound reacts with a naphthol, under basic conditions to produce a dye molecule. 

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