Diphenyl crystallises in large brilliant white or colourless leafy crystals, of an agreeable odour, easily soluble in alcohol and ether, but quite insoluble in water. It melts at 70.5° and boils at 254°. Chromic acid oxidises it in glacial acetic solution to benzoic acid, one phenyl group being destroyed. Parachlor-diphenyl, CH,CI.C6H5, prepared from phenyl-phenol (§ 1144) by means of PC15, crystallises in plates, melting at 75° and yielding parachlor-benzoic acid on oxidation. Brom diphenyls.—Parabrom-diphenyl, CH,Br.C6H5, obtained by treating one molecule of diphenyl in solution in carbonic disulphide with a molecule of bromine, forms colourless crystals, melting at 89° and boiling at 310°; it gives parabrom-benzoic acid on oxidation. Diphenyl treated under water with excess of bromine yields dibrom-diphenyl, CH,Br.CH,Br; it forms large colourless prisms, almost insoluble in alcohol, melting at 64° and boiling between 355°-360°. 1143. Nitro-diphenyls.-1. Paranitro-diphenyl, CH1(NO2). C6H5, resulting from the direct action of cold concentrated nitric acid on the hydrocarbon, crystallises in colourless needles, melting at 113° and boiling at 340°, and giving paranitro-benzoic acid on oxidation with chromic acid. 2. The isomeric metanitro-diphenyl is obtained by distilling a mixture of sand, metanitro-benzoic acid, and potassium phenylate; it forms large prisms, melting at 86° and much more readily soluble in alcohol than the para compound, C12Hg(NO2)2. Two isomeric dinitro-diphenyls result from the action of excess of cold fuming nitric acid on diphenyl. The para compound is only slightly soluble in alcohol, and crystallises in colourless needles, melting at 233°, which by oxidation yield paranitro-benzoic acid. The isodinitro-diphenyl is easily soluble in alcohol, and melts at 93.5°. Amido-diphenyls. Paranitro-diphenyl is reduced by tin and hydrochloric acid to para-amido-diphenyl, CH,(NH2).CН5, crystallising in colourless needles, melting between 49°-50°; and the two dinitro-diphenyls give by incomplete reduction the isomeric compounds C12H,(NO2).(NH2), para-amido-nitro-diphenyl, melting at 1980, and isamido-nitro-diphenyl, at 97°-98°. Both compounds crystallise in red needles.. Paradiamido-diphenyl, CH4.(NH2).CH,(NH2), or benzidine, is formed by the reduction of paradinitro-diphenyl with tin and hydrochloric acid, as well as by the action of acids on the isomeric hydrazobenzene (§ 975), also by heating azobenzene with concentrated hydrochloric acid to 115° and by the decomposition of brom-aniline with sodium ($ 986). It crystallises in silvery plates, melting at 118°, which may be partly sublimed unchanged; it is soluble in hot water, more readily in alcohol and ether, and forms difficultly soluble salts, e.g. almost insoluble in water and alcohol. It combines with ethylic COMPOUNDS OF CONJUGATED BENZENE NUCLEI. 1141. Several benzene nuclei can unite to form fresh groups, the union being either direct, e.g. These groups may be designated as conjugated benzene nuclei. The hydrocarbons derived from them are capable of the same substitutions as benzene itself, so that, on account of the complication of the carbon nucleus, an extraordinary number of isomeric compounds appears to be possible, although, from the short time these bodies have been worked at, only a moderate number are known at present. COMPOUNDS CONTAINING TWO BENZENE GROUPS. 1142. When the vapour of benzene is sent through tubes filled with pumice and heated to redness, diphenyl is formed along with free hydrogen and other products: The same hydrocarbon is also formed by acting on an ethereal solution of brom-benzene with sodium : also by the dry distillation of a mixture of potassic phenylate and potassic benzoate or oxalate: 2C6H5.OK + K2C2O1 = 2K2CO3 + C12H10 and is also found in small quantity in coal-tar oils. Diphenyl crystallises in large brilliant white or colourless leafy crystals, of an agreeable odour, easily soluble in alcohol and ether, but quite insoluble in water. It melts at 70.5° and boils at 254°. Chromic acid oxidises it in glacial acetic solution to benzoic acid, one phenyl group being destroyed. Parachlor-diphenyl, CH4Cl.C6H5, prepared from phenyl-phenol (§ 1144) by means of PC15, crystallises in plates, melting at 75° and yielding parachlor-benzoic acid on oxidation. Brom diphenyls.-Parabrom-diphenyl, CH,Br.CH,, obtained by treating one molecule of diphenyl in solution in carbonic disulphide with a molecule of bromine, forms colourless crystals, melting at 89° and boiling at 310°; it gives parabrom-benzoic acid on oxidation. Diphenyl treated under water with excess of bromine yields dibrom-diphenyl, CH,Br.CH,Br; it forms large colourless prisms, almost insoluble in alcohol, melting at 64° and boiling between 355°-360°. 1143. Nitro-diphenyls.-1. Paranitro-diphenyl, CH1(NO2).C6H5, resulting from the direct action of cold concentrated nitric acid on the hydrocarbon, crystallises in colourless needles, melting at 113° and boiling at 340°, and giving paranitro-benzoic acid on oxidation with. chromic acid. 2. The isomeric metanitro-diphenyl is obtained by distilling a mixture of sand, metanitro-benzoic acid, and potassium phenylate; it forms large prisms, melting at 86° and much more readily soluble in alcohol than the para compound, C12H,(NO2)2. Two isomeric dinitro-diphenyls result from the action of excess of cold fuming nitric acid on diphenyl. The para compound is only slightly soluble in alcohol, and crystallises in colourless needles, melting at 233°, which by oxidation yield paranitro-benzoic acid. The isodinitro-diphenyl is easily soluble in alcohol, and melts at 93.5°. Amido-diphenyls. Paranitro-diphenyl is reduced by tin and hydrochloric acid to para-amido-diphenyl, CH4(NH2).C6H5, crystallising in colourless needles, melting between 49°-50°; and the two dinitro-diphenyls give by incomplete reduction the isomeric compounds CH(NO2).(NH2), para-amido-nitro-diphenyl, melting at 198°, and isamido-nitro-diphenyl, at 97°-98°. Both compounds crystallise in red needles. Paradiamido-diphenyl, CH4.(NH2).CH (NH2), or benzidine, is formed by the reduction of paradinitro-diphenyl with tin and hydrochloric acid, as well as by the action of acids on the isomeric hydrazobenzene (§ 975), also by heating azobenzene with concentrated hydrochloric acid to 115° and by the decomposition of brom-aniline with sodium (§ 986). It crystallises in silvery plates, melting at 118°, which may be partly sublimed unchanged; it is soluble in hot water, more readily in alcohol and ether, and forms difficultly soluble salts, e.g. almost insoluble in water and alcohol. It combines with ethylic iodide to form diphenyl-diethyl diammonic iodide, from which alkalies liberate diethyl benzidine: CH,.N.(C2H)H CH,.N.(C2H)H which again, by a repetition of the treatment, yields tetraethyl benzidine, and this further combines with methylic iodide, forming tetraethyldimethyl benzidine diiodide: C6H4.N(C2H5)2.CH2I CH.N(C2H)2.CH3I An aqueous solution of benzidine is converted by nitrous acid into tetra-azodiphenyl nitrate: C6H4.N2.O.NO2 C6H4.N2.O.NO2 which, by addition of ether alcohol, is precipitated in yellowish explosive needles. Carbazol, or imido-diphenyl, NH, is obtained from that portion of coal tar boiling between 320°-360° by addition of picric acid to the solution of this fraction in toluol, when the salt C12Hg.NH2.O.C6H2(NO2)3 separates in large red needles, melting at 182°. Ammonia liberates from this salt free carbazol, which crystallises from hot alcohol or benzene in colourless plates, melting at 238° and boiling between 354° and 355°. It scarcely possesses basic properties, but dissolves in sulphuric acid with production of yellowish solutions. By heating with hydriodic acid and phosphorus at 240° it is converted into carbazoline, C12H15N, a basic body crystallising in prisms, melting at 99°, and boiling at 297°. 2 Another method for the production of carbazol consists in passing the vapour of aniline or diphenylamine through ignited tubes: An isomer of carbazol, acridine, is also found in the 320°-360° fraction of coal tar, from which it may be extracted by dilute sulphuric acid. It crystallises in colourless rhombic crystals, melting at 107°, subliming at 100°, and boiling above 360°. It is easily soluble in alcohol and ether, and is specially characterised by the insolubility of its chromate. When brought in contact with the skin it causes great irritation and burning pain. 1144. Diphenyl sulphonic acids result by heating diphenyl with concentrated sulphuric acid. By excess of acid diphenylene disulphonic C6H1.SO2.OH acid, , is alone produced; by excess of diphenyl, howC6H4.SO2.OH ever, a mixture of the latter with paraphenyl phenylene sulphonic acid, CH5.CH,.SO.OH. Since the copper salt of the monosulphonic acid is difficultly soluble even in boiling water, whilst that of the disulphonic acid is readily soluble, they may be separated without any difficulty. The disulphonic acid crystallises in prisms, melting at 72.5° and readily soluble in water. Phenyl Phenols and Oxides.-The corresponding phenols are produced by melting the potassium salts of the diphenyl sulphonic acids with potash and decomposition of the products with dilute sulphuric acid. 12 Phenyl-phenol, C12H10O = CH5.CH.OH, or diphenylol, prepared from phenyl phenylene sulphonic acid, forms colourless microscopic needles, melting at 164°-165°, very volatile in steam, and boiling at 305° or 308°. 2 = Diphenol, CH100, HO.CH.CH,.OH, in addition to its production from diphenylene disulphonic acid, is also obtainable by boiling tetrazodiphenyl nitrate with water: C6H4.(N2).O.NO, C6H4.(N2).O.NO2 + 20H2 = 2NO2OH + 2N2 + | C6H4.OH C6H4.OH It crystallises in colourless plates, which do not decompose on sublimation. Diphenylene oxide, C12H,O= | CHA O, results when phenol is heated with plumbic oxide, or phenyl phosphoric ether with excess of lime (§ 961). It is insoluble in water, soluble in alcohol, ether, and benzene, from which it crystallises in plates of 80°-81° melting point, boils at 287°, and possesses an agreeable odour. Phenyl sulphide (§ 962) is decomposed when its vapour is passed through red-hot tubes into hydrogen and diphenyl sulphide, CHA >S, colourless needles melting at 97°. Caroulignone, C16H1606, is a blue substance insoluble in alcohol and ether, obtained during the purification of raw pyroligneous acid, and which is precipitated from its phenol solution by alcohol in brilliant steel blue needles. It is converted by hydric sulphide or by zinc and hydrochloric acid into hydrocaroulignone, C16H1806, which further, by heating with hydrochloric acid to 200°, yields methyl chloride and hexahydroxy-diphenyl, of which body hydrocoroulignone is the tetramethyl ether. The reaction is represented by the equation: C12H(OH)2(O.CH3), + 4HCl = 4CH,Cl + C12H,(OH) Hexahydroxy-diphenyl crystallises in silvery plates, soluble in water, alcohol, and ether. It produces a beautiful blue violet colour with dilute potash solution. 4 6. |