Pyrogallol reaction with

Group III comprises tanning materials containing tannins derived from pyrogallol, and are not precipitated by bromine water and give a bluish-black coloration with ferric alum. These also are subdivided into (a) those which give the above characteristic reaction with nitrous acid, and (6) those which give no reaction or only a brown colour. 

Except for ET reactions with strong oxidants, 02 is not very reactive (for a compilation of rate constants, see Bielski et al. 1985). For example, practically no reaction has been detected with amino acids (Bielski and Shiue 1979), and there is no reaction to speak of with the DNA constituents, that is, it is also practically unreactive towards DNA. However, where substantial reactivity has been recognized, its main route of reaction seems to be by addition. This has not only been proposed for its reaction with pyrogallol and the propyl ester of gallic acid [k = 3.4 x 10s and 2.6 x 10s dm3 mol1 s 1, respectively cf. reactions (67)-(71) Deeble et al. 1987, 1988], but it seems that an addition reaction triggers a number of chain reactions (von Sonntag et al. 1993, see below). 

Attempts to use the diethylzinc-pyrogallol (2 1) catalyst to copolymerise propylene sulphide and carbon dioxide failed, since the content of propylene thiocarbonate units in the copolymers formed was small and did not exceed 10 mol.-%. It has also been observed that the presence of carbon dioxide in this copolymerisation system causes a lowering of the molecular weight and yield of the copolymer formed. Thus, it has been suggested that propylene sulphide homopolymerisation was favoured over cross-propagation with carbon dioxide in the presence of a zinc-based coordination catalyst because of higher HSAB symmetry of the system in the former case. The zinc atom in the Zn-S unit of the catalyst is a rather soft acid and will prefer reaction with a soft base such as propylene sulphide rather than with hard carbon dioxide. The presence of a hard acid centre in the triethylaluminium-based catalyst should result in an increase in the affinity of the catalyst towards carbon dioxide [247],... 

These pyrones undergo Diels-Alder reactions with electron-deficient alkenes with loss of COj and formation of an aromatic ring. Thus reaction with 1,1-dimethoxyethylene (11, 279-281) provides a regiospecific route to methyl salicylates (e.g., 3), which are convertible in several steps into catechol derivatives (4) or by decarbomethoxylation into phenol ethers (5). Similar reactions with vinylene carbonate or 1, 1,2-trimethoxyethylene provide regiospecific routes to phenols, differentially protected derivatives of catechol, resorcinol, or pyrogallol (equation II). 

In an acid medium (HCl, H2SO4), pyrogallol reacts with Ta(V) to form a yellow complex, whose absorption maximum occurs in the near-ultraviolet. This reaction has long been the basis of a simple and selective method for determining Ta [87,88]. 

The absorption spectrum of the Ta complex and the interferences owing to other elements (particularly Nb and Ti) vary according to the reaction conditions. A solution of 4 M HCl and 0.02 M (NH4)2C204 is a suitable medium, since the colour from pyrogallol complexes with niobium and titanium is insignificant. In this medium, a ternary tantalum complex with pyrogallol and oxalic acid, and the colourless Nb oxalate complex are formed. To reduce the interference by Nb, tartrate is sometimes added. 

The o-quinone heterodienes generated electrochemically from pyrogallols undergo in situ regiospecific inverse electron demand DA reactions with enamines leading to a wide range of... 

PYROGALLOL (87-66-1) Combustible solid. Dust or powder forms explosive mixtures with air. Violent reaction with peroxyfuroic acid. Incompatible with strong oxidizers, alkalis, alkylene oxides, ammonia, amines, antipyrine, epichlorohydrin, iodine, isocyanates, menthol, phenol, potassium permanganate, metallic salts of lead and iron. 

Besides catechol, the potato enzyme attacks pyrogallol, dopa, adrenaline, t3rrosine, and other phenolic compounds. The kinetics of the reactions with various substrates are not easily interpreted. Tyrosine is oxidized at a slow, linear rate and catechol is oxidized much more rapidly. p-Cresol, however, is oxidized rapidly only after a lag period. Other phenolic compounds, including resorcinol and hydroquinone, are not oxidized by this enzyme. 

In another stndy, Monirnzzaman et al. [215] explored the use of w/IL microemulsions comprised anionic surfactant, AOT/hydrophobic IL [C mim] [TfjN] (l-octyl-3-methyl imidazolium bis(trifluoromethylsnlfonyl)amide)/water/l-hexanol as the reaction medinm for the enzymatic oxidation of pyrogallol catalyzed by HRP. The results demonstrated that the rate of HRP-catalyzed reactions in IL microemnlsions increases significantly compared with that obtained in conventional oil microemnlsions. It was concluded that a w/IL microemulsion may be a very promising system for performing enzymatic reactions with HRP in ILs media. According to them, the findings will be of valne for the development of ILs... 

The phospha-Mannich condensation of a-, (3- and y-amino acetals, paraformaldehyde and secondary phosphine oxides led to a),(i)-dialko g -all laminomethylphosphine oxides whose reaction with resorcinols or pyrogallol in boiling trifluoroacetic acid afforded (diallg lphosphinoyl-methyl-)(o),a)-diaiylallgrl)ammonium trifluoroacetates (Scheme 41). ... 

After all the hydrogen peroxide is added, the reaction mixture is allowed to cool to room temperature and is then saturated with sodium chloride, after which it is extracted four times with 100-ml. portions of ether. The combined extracts are dried over sodium sulfate. The ether is removed by distillation on a steam bath, and the residue is then distilled under reduced pressure, Pyrogallol monomethyl ether is collected at 136-138°/22 mm. The yield is 38-44.5 g. (68-80%) of a colorless to light t11ow oil which solidifies on standing (Note 4). 

HTAB has been used, on the one hand, to increase the CL intensity of the reaction of 2,6,7-trihydroxy-9-(4 chlorophenyl)-3-fluorene with hydrogen peroxide in alkaline solution, in the presence of traces of Co(II) as a catalyst [43]. As a consequence, a CL method has been established for determination of ultratraces of Co(II). On the other hand, HTAB micelles sensitize the CL oxidation of pyro-gallol with A-bromosuccimide in an alkaline medium [44], while anionic and nonionic surfactants inhibit the CL intensity of this reaction (Table 3). This sensitized process allows the determination of pyrogallol by flow injection in an interval of 5 X 10 7-3 X 10 5 M. 

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