Hunter[26] found that when either of the anilids of orthosulphobenzoic
acid were treated with phosphorus oxychloride, or similar dehydrating
agents, a molecule of water was abstracted with the formation of a new
substance. A careful study of the compound led to the belief that it
was a dianil, and that its formation and structure could be represented
by the equation
C=N.C₆H₅
/ \
CO.NH.C₆H₅ / \
/ / .N.C₆H₅
C₆H₄ = C₆H₄ / + H₂O.
\ \ /
SO₂NH.C₆H₅ SO₂
A corresponding study of the fusible anilid of
paranitroorthosulphobenzoic acid was undertaken.
The method employed in this study was as follows. A tubulated retort
of convenient size was fused onto the inner tube of a small condenser.
This was done to avoid connections, which are nearly always attacked by
the oxychloride. Another satisfactory plan is to have the neck of the
retort of the same size as the inner tube of the condenser. The ends
are placed in contact, and the tubes bound in position by wrapping with
asbestos paper. Over the joint so made, a tight rubber tube is drawn.
[26] Am. Ch. Journ. XVIII-810.
A convenient amount of phosphorus oxychloride (50 c.c.) was placed
in the retort and the anilid (5 gr.) added through the tubulus. On
boiling, with the condenser inverted, the anilid soon dissolved,
with evolution of hydrochloric acid gas, and the solution became
bright yellow in color, sometimes inclining to orange. The boiling was
continued as long as hydrochloric acid was given off. The oxychloride
was then distilled off under diminished pressure, care being taken to
shake the retort constantly during the distillation as violent bumping
is almost sure to occur especially towards the end of the operation.
The product remaining, spattered over the walls of the retort, was a
greenish yellow solid.
Water was then added, and the whole allowed to stand for an hour or
so to thoroughly dissolve the phosphoric acid formed in the reaction.
In case the anilid is not perfectly dry, a much more energetic reaction
occurs, and on distilling off the oxychloride, the product remains as a
dark, gummy mass. This should be spread out on the sides of the retort
while still liquid. On cooling and adding water, this gum gradually
disappears, and in its place is found the yellow solid product just
described. The gum appears to be a solution of this substance in
phosphoric acid.
After the substance is filtered off and dried, it can be crystallized
from acetone, benzene, glacial acetic acid or alcohol. From these
solvents it crystallizes in small yellow needles resembling quinone in
appearance.
The crystals obtained form acetone are rather larger than those from
the other solvents, and are more nearly orange in color, apparently
because of their greater compactness. When glacial acetic acid is used,
care must be taken to avoid any unnecessary heating, as continued
heating produces a change that will presently be described. The
substance melts at 208°.
Analysis of the substance resulted as follows: