An analogous synthesis is that of dihydro-m-xylene from methyl heptenone,(CH 3) 2 C:CH (CH2)2.CO CH3.
STYROLENE, C 6 H 5 CH:CH 2, also known as phenylethylene or vinylbenzene, an aromatic hydrocarbon found to the extent of 1 to 4% in storax; it also occurs with crude xylene in coal tar fractions.
XYLENE, or Dimethyl Benzene, C6H4(CH3)2.
Ortho-xylene is obtained from ortho-bromtoluene, methyl iodide and sodium as a colourless mobile liquid boiling at 142°, melting at - 28°, and having a specific gravity of 0.8932 at o°.
Metaor iso-xylene, the most important isomer, may be prepared by nucleus-synthetic reactions, or by distilling mesitylenic acid, C 6 H 3 (CH 3) 2 CO 2 H, an oxidation product of mesitylene, C 6 H 3 (CH 3) 3, which is produced on the condensation of acetone, with lime; this reaction is very important, for it orientates meta-compounds.
Para-xylene is obtained when camphor is distilled with zinc chloride, but it is best prepared from para-brom-toluene or dibrombenzene, methyl iodide and sodium.
(See Indigo.) Isoptahhalic acid is obtained by oxidizing meta-xylene with chromic acid, or by fusing potassium meta-sulphobenzoate, or meta-brombenzoate with potassium formate (terephthalic acid is also formed in the last case).