Improvements in the Manufacture or Production Simultaneously of Pure Ortho-nitro-chloro-benzene and Pure Para-nitro-chloro- benzene.
Year: 1898

page_text: Date of Application, 31st Jan., 1898-Accepted, 26th Mar., 1898
Improvements in the Manufacture or Production Simultaneously
of Pure Ortho-nitro-chloro-benzene and Pure Para-nitro-chloro-
benzene.
I, GEORGE WILLIAM JOHNSON, of 47, Lincoln's Inn Fields, in the County of London,
Patent Agent, do hereby declare the nature of this invention (which has been
communicated to me from abroad by Chemische Fabrik Griesheim, of Frankfort-on-
Maine, in the Empire of Germany) and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement :-
Ortho-nitro-chloro-benzene was first obtained in a pure state by Beilstein and
Kurbatow (Ann. 1876, 182, 107) from para-nitro-meta-chloro-aniline by means of
nitrous acid and alcohol, its fusing point being 32-5 degrees and its boiling point
243 degrees Centigrade. Von Engelhardt and Latschinoff (Zeitschr. f. Ch. 1870, 231)
obtained the same product by the action of phosphor-penta-chloride upon ortho-
nitro-phenol. Both these methods are however expensive and unsuitable for the
production, or manufacture, of the product on a commercial scale.
The direct method by nitrating chloro-benzene whereby, as is known, ortho-nitro-
chloro-benzene and para-nitro-chloro-benzene are obtained, has not, so far, led to the
production of the pure product, because it has not been possible, to separate into its
two constituent parts: the residual oil, remaining after the para-product has been
separated by crystallisation, and consisting of a mixture in approximately equal
proportions of the ortho- and para-derivatives.
The method employed by Jungfleisch (Jahresber. d. Chemie. 1868, 343) only leads
to the obtainment of a product, having its fusing-point at 15 degrees Centigrade (see
Beilstein, Handbuch d. org. Chemie 1896, IIIrd edition, IInd volume, page 83).
Ordinary commercial ortho-nitro-chloro-benzene contains, according to P. Fischer,
(Ber. d. d. Chem. Ges. 1891, 24, 3187), upwards of 15 per cent. of para-nitro-chloro-
benzene. Attempts to separate these, have been made, for example, P. Fischer, l. c.,
describes a method of separating ortho- and para-nitro-chloro-benzene by means of
fuming sulphuric acid, in connection with which the ortho-derivative forms a sulpho-
acid, whilst the para-derivative is alleged to remain in the form of a product
insoluble in water. By this means, however, only a para-sulpho acid, and not the
ortho-nitro-chloro-benzene, is obtained. The method of distillating with wet-steam
has been tried by V. v. Richter (Ber. d. d. chem. Ges. 1871, 4, 463). Besides the
ordinary solid para-derivative, he obtained but very little of the liquid product,
which he supposed to be an ortho-derivative. As, however, the ortho-nitro-chloro-
benzene is not liquid but solid, he only obtained the liquid mixture of both, and no
pure ortho derivative. It has, on the other hand, been proved by Belstein and
Kurbatow (Ann. 1875, 176, 36) that, in this process, both isomerides pass over
simultaneously, so that consequently a separation is not obtained. Even by applying
direct distillation, they have not only not succeeded in separating the products, but
they declare, (1. c.) this method of separating to be altogether excluded, because
according to Jungfleisch, the para-derivative would boil at 242 degrees Centigrade
whereas the ortho-derivative (according to Beilstein and Kurbatow) would have its

page_text: boiling point only one degree higher, namely at 243 degrees Centigrade. They state
therefore that to separate the two bodies by distillation is impossible.
My foreign correspondents have now found that this is not correct their investiga-
tions shewing that the difference between the boiling-points is not one degree, but
amounts to 6° 7°, since para-nitro-chloro-benzene boils at 238.5° Centigrade under
a pressure of 753 m.m., and at 1130 Centigrade under a pressure of 8 m.m. and
ortho-nitro-chloro-benzene boils at 245.5° Centigrade under a pressure of 753 m.m.,
and at 119° Centigrade under a pressure of 8 m.m.
They have further found that this difference is insufficient to admit of technical
separation by means of fractional distillation, because, even after repeated
fractionation, the pure ortho- and para- products cannot be obtained. By a combina-
tion of fractional distillation, however, with fractional crystallisation, they have
found that it is possible to obtain quite pure ortho- and para-nitro-chloro-benzene
from the oily mixture, thus. completely separating the mixture into the two
isomerides.
In order to carry out the method, say 1000 kilos. of the liquid mixture of ortho- and
para-nitro-choro-benzene are submitted to fractional distillation in an efficient
fractionating apparatus either under atmospheric pressure over a naked flame or open
fire or under reduced pressure by means of a steam coil. The first fractions yield, on
cooling, the first crop of pure para-nitro-chloro-benzene, and the last fractions yield
pure ortho-nitro-chloro-benzene which can be separated from the mother-liquor
which may be done by a filter pump, or a centrifugal machine. Further cooling of
the two fractions yields a second crop of para-nitro-chloro-benzene containing the
ortho-compound, and of the ortho-derivative containing the para-compound,
respectively. The fractions corresponding to one another are collected from the
distillation and crystallisation processes, and when they have amounted to say
1000 kilos. they are again fractionated. By systematic fractionation and crystal-
lisation it is possible to finally completely separate the two isomeric derivatives, in
spite of the small difference between their boiling-points.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, I declare that what
I claim is
The manufacture and production simultaneously of pure ortho-nitro-chloro-
benzene and pure para-nitro-chloro-benzene by submitting to fractional distillation,
under atmospheric pressure, or in vacuum, the mixture of ortho- and para-nitro-
chloro-benzenes remaining from the manufacture of para-nitro-chloro-benzene, by
which means the para-nitro-chloro-benzene is accumulated in the first fractions, and
the ortho-nitro-chloro-benzene is accumulated in the last fractions, the two isomerides
being then precipitated from these fractions by fractional crystallisation, and
separated from the oily mother-liquor, which is then further subdivided by fractional
distillation and fractional crystallisation, all substantially as herein before explained.
Dated this 31st day of January 1898.
JOHNSONS & WILCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.