PYROPHORUS (Gr. 7rup,

See also:

• FIRE (in O. Eng. f j'r; the word is common to West German languages, cf. Dutch vuur, Ger. Feuer; the pre-Teutonic form is seen in Sanskrit pu, pavaka, and Gr. irup; the ultimate origin is usually taken to be a root meaning to purify, cf. Lat. purus)

fire, 4 perv, to

See also:

• BEAR
• BEAR, BLACK
• BEAR, BROWN
• BEAR, GRIZZLY
• BEAR, ISABELLINE
• BEAR, WHITE

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 .