Piria reaction

PIRIA REACTION. Formation of arylsulfamic acids or sulfonation pioducts oi both by refluxing aromatic nitro compounds with a metal sulfite and boiling the mixture with dilute add to yield the amines and sulfamic acids. 

Sulfonation of nitroso compounds by sodium hydrogen sulfite leads to amino sulfonic acids by simultaneous reduction.1240 194 When aromatic nitro compounds are subjected to this reaction, sulfonation in the ring is accompanied by formation of arylamine-JV-sulfonic acids (arylsulfamic acids), which on acid fission also give amino sulfonic acids this reaction, known in the literature as the Piria reaction, has been reviewed in papers by Hunter and his co-workers.195... 

Other references related to the Piria reaction are cited in the literature. ... 

Sulfite (Piria method). The reaction of sodium sulfite and bisulfite on an aromatic nitro compound leads to a mixture of amine and aminoaryl-sulfonic acid. 

A relatively unfamiliar method of reduction, which is limited in its applicability although very cheap and convenient where usable, is reduction by means of sodium bisulfite. This reduction, discovered by Piria in 1851, may be represented by the following four reactions ... 

It is. significant in that it gives not only amines but also o- and p-amino sulfonic acids, all in one reaction. It is generally carried out with excess sodium bisulfite (4.5-6.0 moles per mole of nitro compound), usually with the addition of enough caustic soda to form the required amount of neutral sulfite. A solvent, such as ethyl alcohol or pyridine, often helps to speed up the reaction, particularly for nitro compounds that are either difficultly soluble or wettable. It is interesting to note that sulfamic acids have also been isolated from this reaction in certain cases. Examples of nitro compounds that may be reduced by the Piria method are p-nitrotoluene, which forms p-toluidine in about 70 per cent yield p-nitrobenzoic acid, which forms 4-amino-3-sulfobenzoic acid and 4-nitronaphthalic anhydride, which forms 4-amino-3-sulfonaphthalic anhydride. 

It must be emphasized that Piria was unable to describe this reaction in the way that we now express it, as concepts such as substituent, functional group, etc. were still unknown at that time. 

Aliphatic diazonium ions, on the other hand, are extremely unstable. Although they were obtained as very unstable intermediates in 1848 when Piria treated aspartic acid (2-aminosuccinic acid) with nitrosating reagents, leading to malic acid (2-hydroxysuccinic acid), they were not identified directly for almost 120 years. Piria s reaction allowed, in some cases, the substitution of a primary amino group by a hydroxy group. This reaction is also characterized by eliminations and rearrangements (see Chapt. 7). Aliphatic diazonium ions were postulated and subsequently identified as intermediates in the acid-catalyzed decomposition of aliphatic diazo compounds (see Sect. 7.2). 

As mentioned in Section 1.1, the first diazotization of amines, followed by dediazoniation, was carried out by Piria in 1848, well before Griess discovered and isolated aromatic diazo compounds (1858). Piria added an impure HNO3 —HCl solution to a mixture of asparagine and aspartic acid in water and obtained malic acid (7-1). It was not possible for Piria, however, to realize that the primary reaction products were diazonium ions. Yet, Piria s process was one of the few types of reaction via aliphatic diazonium ions that became important for synthetic purposes, after Ingold s group (Brewster et al., 1950) discovered that a-amino acids undergo clean retentive deamination (see Sect. 7.7). 

Orthohydroxy benzyl alcohol, oxybenzylalcohol, or simply phenol alcohol or saligenin was first isolated by Piria in 1843. It can be converted into resin (known as saliretins ) on heating. The reaction between phenol and aldehyde was first reported by von B aeyer in 1872, who used an iron pressure cooker he invented, called a bakelizer, and resulted in a sticky substance that he dismissively called Schmiere . The actual reaction between formaldehyde and phenol was independently studied by Manasse and Lederer in 1894, after formaldehyde became a commercial product. 

Stanislao Cannizzaro (Palermo, Sicily, 1826-Rome, 10 May 1910) studied in Palermo and Naples. In 1847 he took part in the Rebellion. In 1850 he became Piria s assistant in Paris and in 1851 published his first research, on cyanogen chloride and cyanamide, done jointly with Cloez in Chevreul s laboratory. In 1852 he was appointed in Alessandria and in 1853 published an important researdi on the action of caustic potash on benzaldehyde, obtaining potassium benzoate and benzyl alcohol ( Cannizzaro s reaction ) 2C,H5CHO+KOH=C.HsCOOK+C,H8CH,OH. In 1855 he became professor in G noa, where at fimt there was no laboratory, and there he wrote his famous pamphlet. In i860 he joined Garibaldi at Palermo. In 1861 he became professor in Palermo and in 1870 in Rome, where he was created senator. ... 

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