Diazonium aliphatic

Primary aromatic amines differ from primary aliphatic amines in their reaction with nitrous acid. Whereas the latter yield the corresponding alcohols (RNHj — ROH) without formation of intermediate products see Section 111,123, test (i), primary aromatic amines 3neld diazonium salts. Thus aniline gives phcnyldiazonium chloride (sometimes termed benzene-diazonium chloride) CjHbNj- +C1 the exact mode of formation is not known, but a possible route is through the phenjdnitrosoammonium ion tlius ... 

In the presence of proton-donative organic solvents (alcohols), aliphatic amines do not react with diazonium, whereas aromatic amines form mainly triazenes and also para-aminoazo compounds, which subsequently interact slowly with an excess of diazo reagent via N-coupling and form disazo derivatives. 

Certain aliphatic diazonium species such as bridgehead diazonium ions and cyclo-propanediazonium ions, where the usual loss of N2 would lead to very unstable carbocations, have been coupled to aromatic substrates. ... 

Aliphatic primary amines also undergo the diazotization reaction in weakly acidic solution however the resulting aliphatic diazonium ions are generally unstable, and easily decompose into nitrogen and highly reactive carbenium ions. The arenediazonium ions are stabilized by resonance with the aromatic ring ... 

Most functional groups do not interfere with the diazotization reaction. Since aliphatic amines are stronger bases and therefore completely protonated at a pH < 3, it is possible that an aromatic amino group is converted into a diazonium group, while an aliphatic amino group present in the same substrate molecule is protected as ammonium ion and does not react. ... 

Instead of a diazonium salt, a diazo compound is obtained from reaction of a primary aliphatic amine 8 that has an electron-withdrawing substituent at the a-carbon (e.g. Z = COOR, CN, CHO, COR) as well as an a-hydrogen ... 

In some of these papers (e.g., Weiss et al., 1984) it is mentioned that various attempts to synthesize stable aliphatic diazonium salts failed, although the identified reaction products indicated the involvement of aliphatic diazonium ions as intermediates (see also Olah et al., 1966). 

We will review that comparison in the context of the discussion of aliphatic and inorganic diazonium ions in our second book (Zollinger, 1995, Sec. 5.3). 

The reaction of azide ions with aliphatic diazo compounds was investigated by Kirmse et al. (1979 for a discussion see Zollinger, 1995, Sec. 6.1). Here we mention only that cyclopropanediazonium ions react similarly to the aromatic diazonium ions, i.e., by TV-coupling to 1-cyclopropylpentazene and dediazoniation to cyclopropyl azide. In about 60% of the 1-cyclopropylpentazene the cyclopropyl azide is formed directly by dediazoniation of the original diazonio group, while in 40% the route is via the cyclopropylpentazole. 

I hope therefore that, in the not too distant future, an expert on the modeling of organic reactions in solution will investigate the dediazoniation of aromatic or aliphatic diazonium ions in water. 

Compounds acting as coupling components must have a high electron density on the reacting carbon atom. Therefore diazonium ions react only at aliphatic carbon atoms which are activated by electron-withdrawing groups (usually acyl or nitro). There is... 

Primary aromatic amines (e.g., aniline) and secondary aliphatic-aromatic amines (e. g., 7V-methylaniline) usually form triazenes in coupling reactions with benzenedi-azonium salts. If the nucleophilicity of the aryl residue is increased by addition of substituents or fused rings, as in 3-methylaniline and 1- and 2-naphthylamine, aminoazo formation takes place (C-coupling). However, the possibility has also been noted that in aminoazo formation the initial attack of the diazonium ion may still be at the amine N-atom, but the aN-complex might rearrange too rapidly to allow its identification (Beranek and Vecera, 1970). 

Diazonium ions generated from ordinary aliphatic primary amines are usually useless for preparative purposes, since they lead to a mixture of products giving not only substitution by any nucleophile present, but also elimination and rearrangements if the substrate permits. For example, diazotization of n-butylamine gave 25% 1-butanol, 5.2% 1-Chlorobutane, 13.2% 2-butanol, 36.5% butenes (consisting of 71% 1-butene, 20% trans-2-butene, and 9% cw-2-butene), and traces of butyl nitrites. ... 

Aromatic diazonium salts can, of course, be isolated (see Chapter 13), but only a few aliphatic diazonium salts have been prepared (see also Ref. 383). For reviews see Laali, K. Olah, G.A. Rev. Chem. Intermed., 1985, 6, 237 Bott, K. in Patai Rappoport The Chemistry of Functional Groups, Supplement C, pt. 1 Wiley NY, 1983, p. 671 Bott, K. Angew. Chem. Int. Ed. Engl., 1979, 18, 259. The simplest aliphatic diazonium ion CH3N2 has been prepared at — 120°C in superacid solution, where it lived long enough for an nmr spectrum to be taken Berner, D. McGarrity, J.F. J. Am. Chem. Soc., 1979, 101, 3135. 

When primary aromatic amines are treated with nitrous acid, diazonium salts are formed. The reaction also occurs with aliphatic primary amines, but aliphatic diazonium ions are extremely unstable, even in solution (see p. 448). Aromatic diazonium ions are more stable, because of the resonance interaction between the nitrogens and the ring ... 

If an aliphatic amino group is to a COOR, CN, CHO, COR, and so on, and has an a hydrogen, treatment with nitrous acid gives not a diazonium salt, but a diazo compound Such diazo compounds can also be prepared, often more conveniently, by treatment of the substrate with isoamyl nitrite and a small amount of acid. Certain heterocyclic amines also give diazo compounds rather than diazonium salts. ... 

There are many preparations of diazonium salts listed in Organic Syntheses, but they are always prepared for use in other reactions. We do not list them here, but under reactions in which they are used. The preparation of aliphatic diazo compounds can be found in OS III, 392 IV, 424. See also OS VI, 840. 

Aliphatic primary and secondary amines primarily react with the diazonium compound fast black salt K to yield colored triazene derivatives [1] according to the following scheme ... 

The first widely used intermediates for nucleophilic aromatic substitution were the aryl diazonium salts. Aryl diazonium ions are usually prepared by reaction of an aniline with nitrous acid, which is generated in situ from a nitrite salt.81 Unlike aliphatic diazonium ions, which decompose very rapidly to molecular nitrogen and a carbocation (see Part A, Section 4.1.5), aryl diazonium ions are stable enough to exist in solution at room temperature and below. They can also be isolated as salts with nonnucleophilic anions, such as tetrafluoroborate or trifluoroacetate.82 Salts prepared with 0-benzenedisulfonimidate also appear to have potential for synthetic application.83... 

With simple aliphatic amines, the initial diazonium cations (56) will break down extremely readily to yield carbocations (cf. p. 107) which are, for reasons that are not wholly clear, markedly more reactive than those obtained from other fission processes, e.g. RBr- R Bre. Where the prime purpose is the formation of carbocations, the nitrosation is better carried out on a derivative of the amine (to avoid formation of H20) under anhydrous conditions ... 

The instability of aliphatic diazonium cations, in the absence of any stabilising structural feature, is due very largely to the effectiveness of N2 as a leaving group in aromatic diazonium cations, however, such a stabilising feature is provided by the n orbital system of the... 

Here we encounter a specific property of the aromatic compounds. In the aliphatic series diazonium salts are unknown because here substances of the aniline type —C=C— cannot exist. 

Accordingly, many reactions can be performed on the sidewalls of the CNTs, such as halogenation, hydrogenation, radical, electrophilic and nucleophilic additions, and so on [25, 37, 39, 42-44]. Exhaustively explored examples are the nitrene cycloaddition, the 1,3-dipolar cycloaddition reaction (with azomethinylides), radical additions using diazonium salts or radical addition of aromatic/phenyl primary amines. The aryl diazonium reduction can be performed by electrochemical means by forming a phenyl radical (by the extrusion of N2) that couples to a double bond [44]. Similarly, electrochemical oxidation of aromatic or aliphatic primary amines yields an amine radical that can be added to the double bond on the carbon surface. The direct covalent attachment of functional moieties to the sidewalls strongly enhances the solubility of the nanotubes in solvents and can also be tailored for different... 

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