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purpurogallin Chem.|ˌpɜːpjʊərəʊˈgælɪn|
[ad. F. purpurogalline (A. Girard 1869, in Compt. Rend. LXIX. 866), f. purpurine purpurin with inserted -o and -gall (f. pyrogallique pyrogallic a.): named after the unrelated purpurin by analogy with the preparation of that substance by oxidation of alizarin.]
An orange-red crystalline dye, first prepared by mild oxidation of pyrogallol, which is now known to occur in some oak galls and is a tetrahydric phenol, C11H8O5, consisting of fused tropolone and trihydroxybenzene rings.
1872Jrnl. Chem. Soc. XXV. 703 Purpurogallin, the substance obtained by Girard..from pyrogallic acid by the action of silver nitrate, or of potassium permanganate and sulphuric acid, is the principal product of the oxidation effected by lead peroxide, hydrogen peroxide, [etc.]. 1919Ibid. CXV. 1329 The investigation of the red colouring matter derived from the ‘red pea gall’ has..to some extent proved disappointing. It was found that dryophantin..was in no way allied either to the flavones or to the anthocyanins, but..consisted of purpurogallin and two molecules of dextrose. On the other hand, it must be mentioned that purpurogallin has not previously been found in nature. 1968Kirk & Othmer Encycl. Chem. Technol. (ed. 2) XVI. 191 Purpurogallin.., a red-brown to black mordant dye, results from electrolytic and other mild oxidations of pyrogallol. |