Fox, Dorothy Lilian (1930)
The investigation of diaryl ethers.
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Although 4-chloro-4'-bromo-2-nitro- and 4-chloro-4'-bromo-2'-nitrodiphenyl ether can be mononitrated, hot nitration causes elimination of chlorine, bromine being partially eliminated from the resulting 4-bromo-2:2':4'-trinitro-ether with prolonged nitration. Under similar conditions 4-bromo-2-nitrodiphenyl ether readily loses halogen to give pure tetranitrodiohenyl ether. The analogous chlorotrinitro ether obtained from 4:4'-dichloro-2-nitro-diphenyl ether, is alsO only slowly affected by prolonged nitration. 2:4-Dichloro- and 2:4-dibrorao-2':4'-dinitrodiphenyl ether readily nitrate in position 5, but, although subjected to drastic nitration at 100[degrees] over 90[percent] pure unchanged ether was obtained at the end in each case. 4-Chloro~2-nitra-4'-methyldiphenyl ether is converted by cold concentrated sulphuric acid into 2'-nitro-4'-methyldiphenyl ether 4-sulphonic acid, chlorine being eliminated. Similarly 4-bromo-2'-nitro-4'-methyldiphenyl ether is converted into 2'-nitro-4'-methyldiphenyl ether 4-sulphonic acid. Neither 4-chloro-2'-nitro-4'-methyl- or 4-bromo-2-nitro-4'-methyldiphenyl ether are affected by sulphuric acid, nor are most halogeno ethers examined. Nitration of 4-chloro-2-nitro-4'-methyldiphenyl ether and the corresponding 2'-nitro ether yields the 2:2'-dinitro ether or 4-chloro-2:6-dinitrophenol according to the conditions used. Under conditions favouring nitrative scission of the mononitro-ethers, the 2:2'-dinitro ether undergoes partial replacement of chlorine by a nitro group.Nitration of 4-bromo-2-nitro-4-methyldiiihenyl ether using glacial acetic acid, gives a 1:1 mixture of mononitration product with unchanged ether. More drastic conditions yield 4-bromo-2:6-dinitrophenol, with a little 4-bromo-2:2':3'-trinitro-4-methyldi-phenyl ether. Mild nitration of 4-bromo-2'-nitro-4'-methyldipheayl ether gives an inseparable mixture but with more drastic nitration 4-bromo-2:6-dinitrophenol is obtained. 2:4-Dinitro-4'-inethyldi-phenyl ether gives 2:4:2':-trinitro- and 2:4:2':3'-tetranitro-4*-methyldiphenyl ether.4-Chloro-2-nitro-2':4'-dimethyl- and 2:4-dinitro-2' :4'-dimethyl ether both mononitrate in position 5' and dinitrate in positions 3': 5'. Similarly 4-bromo-2-nitro-2':4'-dimethyldiphenyl ether mononitrates in position 5', but conditions which favour dinitration in the corresponding compounds cause elimination of the bromine atom, 2:4:5'-trinitro-2':4'-dimethyl together with some 2:4:3':5'-tetranitro-2':4'-dimethyldiphenyl ether being obtained. 2:4:6-Trichloro-, 2:4:6-tribromo- and 4-chloro-2:6-dibromo-2' 4'-dinitrodiphenyl ether mononitrate in position 3, the 4-chloro-2-bromo-dinitro ether in position 5, while 2:4-dichloro-S-bromo-2':4'-dinitrodiphenyl ether mononitrates partly in position 3 and partly in position 5, a mixture being obtained. No elimination of halogen takes place. The position of entrant nitro-groups is frequently determined by means of a piperidine scission.
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Institution: University of London, Bedford College (United Kingdom).