A Manual of the Chemistry of the Carbon Compounds

3U TEE CBEMISTUY OF
oxidation a monobasic, a bibasic, and a tribasic acid, one alcoholradical
after the other being oxidized to carboxyl.
But we are not only able thus to fix the number of the alcoholradicals,
but in many cases we are in a position to determine the
relative positions of these radicals, as well as that of other groups
replacing hydrogen in benzene, as the following examples will
show;—
l
. u, 1,2. 1,3. 1,4.
6 *(OH Hydroquinone. Pyrocateehin. Besorcin.
Ortho-iodophenoL Meta-iodophenoL Para-oidophenol,
Salicylic Acid. Oxybeuzoic Acid.
Orthoxylene. Isoxylene, Methyl-toluene.
L>U.Utt pilfi,fli;p \0;A Tflnnhthfllin Anid -lerepninauo
C H
« «{ UU.UH AClu,
In phthalic acid, the two carboxyls occupy the positions 1,2, This
we know from the fact that tins acid is obtained by the oxidation
of naphthalene C1(,H8, a hydrocarbon of known constitution, and in
which, as will be shown further on, two carbon-atoms are linked to
two adjoining atoms of the aromatic nucleus,
Isophthalic acid, belonging to the series 1, 3, is obtained by
oxidizing isoxylene; this hydrocarbon has been prepared from mesitylene
or trimethyl-benzeue, in which the three methyls have the
symmetrical positions 1, 3, 5. This follows from the formation
of masitylene, which is obtained by heating acetone with sulphuric
acid (page 15S), three molecules losing three molecules of water, and
the residues joining together thus;—
CHa
CH8
C=CH
\" =31^0+ 3 0 / \
CO HO C
S CH8
On oxidizing mesitylene, we obtain monobasic mesitylenic acid
(CO.OH
CaH8-< CHS which, when heated with quicklime, is resolved into