A Manual of the Chemistry of the Carbon Compounds

THE CARBON COMPOUNDS, 319
OF BENZENE.
Monoehlorobenzene CLHtCL—To obtain chlorine substitution-products,
chlorine is passed into benzene in presence of a little iodine, the
first product being monoehlorobenzene, a colourless liquid, smelling
like bitter almonds, and boiling at 138°. The same substance is produced
by the action of phosphorus pentachloride upon phenol.
Monoehlorobenzene is not acted upon by heating it with silver salts
or alcoholic solutions of potash, ammonia, and potassium acetate.
When treated with sodium-amalgam, it is reconverted into benzene.
By the further action of chlorine upon benzene, the following
bodies have been obtained; they are all white crystalline solids:—
Dichlorobenzene. , . C8H4C12
Trichlorobenzene . . CjHgClg
Tetrachlorobenzene . CCB^C14
Pentachlorobenzene . CjHClj
Hexachlorobenzene . C0Cle
53°
17
139
74
226
171'
206
240
272
326
Hexchlorobenzene is also formed when the vapour of chloroform
CHClg, or tetrachlorethene CCl^, is passed through red-hot tubes.
Monobromobenzene C6HjBr is slowly formed by mixing bromine
with benzene, and exposing the mixture to tho daylight. It is a
liquid resembling chlorobenzene, and boiling at 154°.
Dibromobenzene C0H4Bry—When benzene is heated with six times
its weight of bromine, it yields two isomeric bibromobenzenes, which
may be separated by fractional distillation.
Paradtbromobenzew crystallizes in large colourless prisms, melting
at 89°, and boiling at 219°,
Orthodibromdbenzene is a liqnid boiling at 213°, and solidifying at
a low temperature to crystals, melting at -1°.
Metadwromobenzcne has been produced by converting aniline into
dibromo-aniline, and acting on this compound with an alcoholic
solution of nitrous acid. Metadibromobeuzeno is a colourless liquid,
boiling at 215°, and not solidifying even at - 28°,
When benzene is heated with an excess of bromine, the higher
substitution-products ore formed, which are colourless, crystalline
solids. •
Moniodobenzem C8H&I.~-Iodine olono does not act upon benzene,
even at a high temperature; but in presence of iodic acid, substitution'products
are formed. The iodic acid acts as oxidizing agent,
taking hydrogen away, in which place iodine enters. At the same
time, a considerable quantity of carbon dioxide is formed, a part of the
benzene being destroyed by oxidation. Moniodobenzene is a colourless
liquid, which assumes a reddish colour on exposure to the light.
It boils at 185°, and is as stable a compound as chlorobenzene.
The mo3t convenient method to prepare this compound in quantity