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PYROPHORUS (Gr. 7rup, fire, 4 perv, t...

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Originally appearing in Volume V22, Page 695 of the 1911 Encyclopedia Britannica.
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PYROPHORUS (Gr. 7rup, fire, 4 perv, to bear), a substance which spontaneously inflames on contact with the air. One of yellow colour and blue fluorescence. Fisetin or 3.3'•4'-trioxyflavonol, C15H30O6, occurs in the wood of Quebracho colorado, and can be obtained by heating fustic with dilute acids. It crystallizes in pale yellow needles. In dilute alcoholic alkalis it shows a dark green fluorescence. On fusion with caustic alkalis it yields phloroglucin, resorcin and protocatechuic acid, whilst if air be passed through its alcoholic solution it yields protocatechuic acid and resorcin. It is obtained synthetically from 2-oxy-3.4-dimethoxy-4-ethoxy-chalkone. The various steps in this synthesis are shown below, since the method employed is applicable to other members of the group. C2H5 C6H3' COCH3+OHC' CsH3(OCH3)2 --~ C2H5 C6H3' CO' CH : C H' C6H3(OCH3) 2 110/ 0 CH'C6H3(OCH3)2C2HSO' " \CH'C6H3(OCH3)2 O/C.VOH \C0/H2 0 C2H5ol \CH'C6H3(OCH3)2 This structure of the fisetin molecule was confirmed by Herzig (Monats., 1891, 12, p. 177), who showed that the tetraethyl ether of fisetin on hydrolysis with alcoholic potash gave diethylprotocatechuic acid and diethylfisetol, the latter on oxidation yielding ethyl-f3-resorcylic acid, which had been previously obtained by oxidizing resacetophenone ethyl ether. Luteolin or 1.3.3'•4'-tetroxyflavone, C,5H1006, is found in the weld obtained from Reseda luleola. It crystallizes in small yellow needles, which dissolve in solutions of the caustic alkalis with a bright yellow colour. On fusion with caustic alkalis it yields phloroglucin and protocatechuic acid. It is obtained synthetically from I.3.3''4'-tetramethoxy-flavanone by bromination, the tribromo-compound being decomposed by the successive use of alcoholic potash and concentrated hydriodic acid. Quercetin or I.3.3'•4'-tetroxyflavonol, C15H1007, is a decomposition product of quercitrin rind, and is found in many plants. It is obtained by the hydrolysis of quercitrin with dilute sulphuric acid. It is a pale yellow crystalline powder. Alcohol hydrolyses it to protocatechuic acid and phloroglucin. It is prepared synthetic-ally from 2-hydroxy-3.4.4'•6'-tetramethoxy-chalkone. Rhamnetin, C,5H906.00H3, the monomethyl ether, is a pale yellow powder. Rhamnazin, C15H5O5(OCH3)2, the dimethyl ether, crystallizes in yellow needles. Morin or I.3.2'•4'.tetroxyflavonol, C,5H,007, occurs In the wood of Autscorpis integrifolia, and crystallizes in long yellow needles, which on fusion with caustic alkali decompose into phloroglucin, resorcin and oxalic acid. On reduction with sodium amalgam in alkaline solution it yields phloroglucin and ,B-resorcylic acid. It yields a tetramethyl ether and a penta-acetate. It has been synthesized from 1.3.2'•4'-tetramethoxy flayanone by converting this into its isonitroso compound, which yields morin trimeth l ether on hydrolysis by sulphuric acid. Myricetin or 1.3'3'4 •5'-penta-oxy flavonol, C15H1008, found in the rind of Myrica nagi and also in Sicilian sumach, crystallizes in yellow needles which dissolve with a green colour in dilute alkalis. On fusion with caustic alkalis it yields gallic acid and phloroglucin. The parent substance of the group, namely chroman (annexed formula), was obtained by J. v. Braun and A. H2•CH2 Steindorff in 1905 (Ber., 38, p. 850) by diazotizing I , ortho-amino-y-chlorpropylhenzene and heating O—CH2 the resulting chlorpropylphenol with a caustic alkali. It is a colourless oil which boils at 214–215e C. and possesses a characteristic peppermint odour. For the dibenzo-pyrones see XANTHONE.
End of Article: PYROPHORUS (Gr. 7rup, fire, 4 perv, to bear)
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