Phenol is characterized by the readiness with which it forms substitution products; chlorine and bromine, for example, react readily with phenol, forming orthoand parachlorand -bromphenol, and, by further action, trichlorand tribrom-phenol.
By the action of dilute nitric acid; orthoand para-nitrophenols are obtained, the ortho-compound being separated from the para-compound by distillation in a current of steam.
Phenol dissolves readily in concentrated sulphuric acid, a mixture of phenol-orthoand -para-sulphonic acids being formed.
Experience has shown that such mono-derivatives as nitro compounds, sulphonic acids, carboxylic acids, aldehydes, and ketones yield as a general rule chiefly the meta-compounds, and this is independent of the nature of the second group introduced; on the other hand, benzene haloids, amino-, homologous-, and hydroxy-benzenes yield principally a mixture of the orthoand para-compounds.
Soc. 61, p. 367): If the hydrogen compound of the substituent already in the benzene nucleus can be directly oxidized to the' corresponding hydroxyl compound, then meta-derivatives predominate on further substitution, if not, then orthoand paraderivatives.
By further substitution of orthoand para-diderivatives, in general the same tri-derivative [1.2.4] is formed (Ann., 1878, 192, p. 219); meta - compounds yield [1.3.41 and [1.2.
Chem., 18 94 , 49, p. 308), has the advantage of bringing the meta-positions on one side, and the orthoand paraon opposite sides, thus exhibiting the similarity actually observed between these series of compounds.
Three isomers exist, the orthoand para-compounds being the chief products of the direct nitration of toluene.
The diortho and dipara dinitro compounds result from the action of alcoholic potash on orthoand para-nitrobenzyl chlorides.
(1873), 168, p. 271), a behaviour which distinguishes it from orthoand meta-cresol.
Instances of its application are found in the separation of orthoand para-nitrophenol, the o-compound distilling and the p- remaining behind; in the separation of aniline from the mixture obtained by reducing nitrobenzene; of the naphthols from the melts produced by fusing the naphthalene monosulphonic acids with potash; and of quinoline from the reaction between aniline, nitrobenzene, glycerin, and sulphuric acid (the product being first steam distilled to remove any aniline, nitrobenzene, or glycerin, then treated with alkali, and again steam distilled when quinoline comes over).
It is prepared by oxidizing "aniline for red" (a mixture of aniline and orthoand para-toluidine) with arsenic acid (H.
The orthoand para-nitro-benzoic acids can be obtained by oxidizing orthoand para-nitro-cinnamic acids.
The orthoand parasemidines can be readily distinguished by their behaviour with different reagents; thus with nitrous acid the ortho-semidines give azimido compounds, whilst the para-semidines give complex diazo derivatives; with formic or acetic acids the ortho-semidines give anhydro compounds of a basic character, the para-semidines give acyl products possessing no basic character.