Amines acid diazotization

Pyrimidin-5-amine, 4-methylamino-synthesis, 3, 121 Pyrimidin-5-amine, 4-oxo-purfne synthesis from, 5, 582 Pyrimidinamines acylation, 3, 85 alkylation, 3, 86 basic pXa, 3, 60-61 diazotization, 3, 85 Dimroth rearrangement, 3, 86 electrophilic reactions, 3, 68 Frankland-Kolbe synthesis, 3, 116 hydrolysis, 3, 84 IR spectra, 3, 64 N NMR, 3, 64 nitration, 3, 69 Principal Synthesis, 3, 129 reactivity, 3, 84-88 structure, 3, 67 synthesis, 3, 129 Pyrimidin-2-amines alkylation, 3, 61, 86 basic pK , 3, 60 diazotization, 3, 85 hydrogenation, 3, 75 hydrolysis, 3, 84 mass spectra, 3, 66 Pyrimidin-4-amines acidity, S, 310 alkylation, 3, 61, 86 basic pXa, 3, 61 Schifi base, 3, 85 synthesis, 3, 110, 114 1,3,5-triazines from, 3, 518 Pyrimidin-5-amines basic pXj, 3, 61 hydrogenation, 3, 75 reactions... 

If relatively basic and nucleophilic aromatic amines are diazotized in nitrosylsul-furic acid, C- instead of TV-nitrosation takes place as shown by Blangey (1938) for 1-naphthylamine, which gave in this system 4-nitroso-l-naphthylamine. A possible mechanistic explanation of Blangey s observation is given in Section 3.2. 

Spengler and Jumar [90] used a spectrophotometric method and thin layer chromatography to determine carbamate and urea herbicide residues in sediments. The sample is extracted with acetone, the extract is evaporated in vacuo at 40°C and the residue is hydrolysed with sulphuric acid. The solution is made alkaline with 15% aqueous sodium hydroxide and the liberated aniline (or substituted aniline) is steam distilled and collected in hydrochloric acid. The amine is diazotized and coupled with thymol, the solution is cleaned up on a column of MN 2100 cellulose power and the azo-dye is determined spectrophotometrically at 440nm (465nm for the dye derived from 3-chloro- or 3.4-dichloroaniline) with correction for the extinction of a reagent blank. 

The reaction sequence is the usual one. The hydrochloride of the aromatic amine is diazotized with sodium nitrite/hydrochloric acid and subsequently coupled onto a Naphthol AS derivative. 

Bersier and coworkers29 published a list of 20 aromatic and heteroaromatic amines whose stabilities in diazotization systems have been investigated. Aqueous systems are harmless, even with amines containing one or two nitro groups (provided that they can be diazotized at all in water). In 96% sulfuric acid, diazotizations of aminoanthraquinones are not dangerous this is also the case for heteroaromatic amines in mixtures of sulfuric acid... 

Diazotization of aminothiophene and the Hurd-Mori reaction <1955JA5359> are two popular methods for synthesis of thieno[2,3- -l,2,3-thiadiazoles. Amine 128 gave only a poor yield of methyl thieno[2,3-/7]-l,2,3-thiadiazole-6-carbox-ylate 131a when subjected to acidic diazotization conditions (Scheme 14). The fully substituted thiophenes 129 and 126 underwent cyclization in much greater yields under similar conditions <1999M573>. Protected amines 127 and 130 also gave a better yield of the cyclized product than the unprotected amine 128 <1999JHC761>. 

Aryl fluorides also may be prepared from arenamines by way of dia-zonium salts if the procedure is slightly modified. The amine is diazotized with nitrous acid in the usual way then fluoroboric acid or afluoroborate salt is added, which usually causes precipitation of a sparingly soluble diazonium fluoroborate. The salt is collected and thoroughly dried, then carefully heated to the decomposition point—the products being an aryl fluoride, nitrogen, and boron trifluoride ... 

While the process at the cathode always ends finally in withdrawal of oxygen or in taking up of hydrogen, the number of possible reactions at the anode—aside from solution-phenomena, which are without interest here—is a much greater one. For, each ion which is capable of substituting can pass into the reactive state at the anode and produce reactions which cannot be numbered with the real oxidations. In the first place numerous substitutions can occur in difficultly oxidizable bodies, especially aromatic compounds, for instance the chlorination of phenols and phthale ins, nitration of acids, diazotizing of amines, etc. Substitution and oxidation processes often occur simultaneously, as in the electrolytic formation of iodoform from alcohol. 

Hydrolysis of acid chlorides, acid anhydrides, esters and carboxamides leads to the carboxylic acid, although these compounds are often derived from a carboxylic acid group in the first place (Scheme 5.5). Nitriles are usually derived from amines via diazotization and reaction with copper(I) cyanide (see Chapter 8) and so the hydrolysis of a nitrile group is of more value. In all cases, alkaline hydrolysis gives the salt of the acid, from which the free acid is obtained by addition of mineral acid. 

When 2, 3, 5 -tri-0-acetyladenosin-8-amine is diazotized with sodium nitrite in 40% fluoro-boric acid at 20 °C, 2, 3, 5 -tri-0-acetyl-8-fluoroadenosine (3) is obtained in approximately 10% yield. 8-Fluoroinosine and adenin-8-ol are also obtained as byproducts. 

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. 

Diazonium fluoroborates from some heterocyclic amines are so unstable that they cannot be obtained dry and these are decomposed, whilst still moist with ether, in light petroleum or xylene. Indeed all isolated diazonium fluoroborates should be treated as potentially unstable until their stability has been determined on small samples for instance, an explosion has been reported1250 with 3-pyridinediazonium fluoroborate1249 that was still moist with solvent diazonium fluoroborates from oc- and y-amino N-heterocycles usually decompose at or below 20°, so the amines are diazotized in tetrafluoroboric acid and decomposition is induced by warming the diazotization solution.1246,1247... 

The so-called direct method can be used with any amine that dissolves in aqueous acid. A cold solution of sodium nitrite is dropped into a cold solution of the arylamine in aqueous mineral acid. Diazotization is usually carried out at 0° because free nitrous acid is most soluble at low temperatures also the diazonium salts produced are most stable at low temperatures. When these salts are relatively stable, diazotization may be conducted at somewhat higher temperatures, sulfanilic acid, for instance, even at 10-15° in special cases even temperatures of 30-40° may be used. The higher temperatures are permissible when the diazonium salt is sufficiently stable and the base to be diazotized is too sparingly soluble at 0°. 

In the first step of analysis, the prescribed solution is acidified with dilute hydrochloric acid R, and 0.2 ml of sodium nitrite solution R is added. The primary aromatic amine is diazotized xmder these conditions (Figure 3.5.2). 

A standard condition has been optimized for this reaction, in which the aryl amine is diazotized in 10 times its amount of acetic acid, followed by the addition of one equivalent of cuprous halide in hydrohalic acid. Under these conditions, the acetate salt of aryl amine is relatively soluble, and less froth and tarry material are formed during diazo transformation. In addition, chlorination, bromination, and iodonation of p-haloaniline to dihalobenzenes under such standard conditions give almost comparable average yields. Other modifications of this reaction include the formation of phenyl selenocyanate by the reaction with potassium selenocyanate, and aryl nitrile by the reaction with nickel cyanide. Moreover, this reaction has been extended to the preparation of phenyl thiocyanate, phenyl isothiocyanate and aromatic sulfonyl chloride. ... 

Today, the GBH reactions are performed by using aryldiazonium tetrafluoroborate salts. An aromatic amine is diazotized at about -10 to 0 C in the presence of at least 3 equivalents of concentrated hydrochloric acid by adding the solution of sodium nitrite [61]. To the aryldiazonium chloride, 50% aqueous solution of tetrafluoroboric acid is added with additional cooling to precipitate the corresponding aryldiazonium... 

Method 3 Deamination of aromatic amines by diazotization in the presence of hypophosphorous acid ... 

The isocyanate vapours are absorbed in an acid solution which converts the vapour into an amine. The amine is diazotized and coupled with V-naphthylethylene diamine and the colour measured in a spectrophotometer. Details of this common method are now given. 

Amine antioxidants Diazotized p-nitroaniline. Mix 5 ml 0.5% p-nitroaniline in 2 N hydrochloric acid with 0.5 ml 5% sodium nitrite, until colourless and 15 min later add 15 ml 20% sodium acetate. ... 

In this method, a polymer is prepared which has certain struc-tiiral features which can be chemically transformed to dye structures in one or more steps. Perhaps the most common class of dyes that have been so synthesized on a polymer backbone is the azo dyes, which are simply formed by the coupling of a polymeric aryl diazon-ium salt with an activated aromatic system. The former are prepared from polymeric aromatic amines by diazotization. Thus polymers and copolymers of 2,2 -di vinyl benzidine (XVl) have been diazotized and coupled with sodium naphthionate, sodium anthranilate and sulfanilic acid to give polymeric azo dyes which act as pH indicators,... 

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