Ladenburg (Ann., 1875, 179, p. 163) to be symmetrical trimethyl benzene; terephthalic acid, the remaining isomer, must therefore be the para-compound.
The identity of the four valencies of the carbon atom follows from the fact that the heats of combustion of methane, ethane, propane, trimethyl methane, and tetramethyl methane, have a constant difference in the order given, viz.
The thermal effects increase as one passes from primary to tertiary alcohols, the values deduced from propyl and isopropyl alcohols and trimethyl carbinol being: - primary =45 08, secondary = 50.39, tertiary = 60.98.
Trimethyl carbinol or tertiary butyl alcohol, (CH 3) 3.
At a temperature of about 300-400° C. the alkyl chloride formed in this reaction attacks the benzene nucleus and replaces hydrogen by an alkyl group or groups, forming primary amines homologous with the original amine; thus methylaniline hydrochloride is converted into paraand ortho-toluidine hydrochloride, and trimethyl phenyl ammonium iodide is converted into mesidine hydriodide.