Improvements in the Treatment of Technical Nitrotoluene.
Year: 1895

page_text: PROVISIONAL SPECIFICATION.
Improvements in the Treatment of Technical Nitrotoluene.
We ARTHUR GEORGE GREEN, F.C.S., F.I.C., of 13 Kings Drive, Heaton
Moor, near Stockport, Consulting Chemist, and HANS BENFEY, Doctor of
Philosophy, of 1 Nelson Street, Oxford Road Manchester both in the County of
Lancaster, Chemist, do hereby declare the nature of this invention to be as
follows:-
No satisfactory method is as yet known for the complete separation of the
ortho- and para-nitrotoluols contained in the mixture of these isomers obtained by
nitration of toluol. The methods at present in use for separating these nitro
compounds or the corresponding toluidines (obtained by reducing the mixture) are
elow, troublesome, and costly, and the object of the present invention is to provide
means for effecting the said separation in a quicker, less troublesome, and more
economical manner than hitherto, the ortho- nitro-toluene being obtained in a
practically pure state whilst the para-isomer is obtained in the form of para-
toluidine.
It has long been known that the nitro-hydrocarbons can be reduced to the
corresponding amines by treatment with alkaline sulphides, and it was by this
method that aniline was first obtained from nitro-benzol by Zinine (Journal für
Practische Chemie [1842] 27-149). Sodium and ammonium sulphides have since
been constantly employed for the reduction of nitro compounds in cases where a
moderated reaction was required, for example in cases where it has been required
to reduce one nitro group in a compound without affecting the reduction of another
reduceable group.
We have discovered that sulphides exert a much more powerful reducing action
upon para-nitro-toluol than upon ortho-nitro-toluol, and upon this our new method
of fractional reduction for the separation of the two isomers is based.
According to our invention the mixture is treated with alkaline or other sulphide
in amount rather more than is sufficient to reduce the whole of the para-nitro-
toluol present in the mixture. A toluidine very rich in the para-isomer is thus
obtained whilst the greater part of the ortho-nitro-toluol remains unreduced. Any
sufficiently soluble sulphide may be employed, such for example as the sulphides,
bydro-sulphides, and poly-sulphides of sodium, potassium, calcium, magnesium, and
the like, but the "alkali waste "of the Le Blanc soda process is eminently adapted
for this purpose.
The following is an example of the manner in which our invention can be carried
into effect, but we do not bind ourselves to the details of this example.
200 lbs. of commercial nitro-toluol (such as can be obtained by nitration of toluol
in the ordinary manner) 750 lbs. of alkali-waste" and 40 gallons of water are
heated for 12 hours or thereabouts in a vessel provided with a stirrer and cohobator.
The toluidine and unaltered nitro-toluol are then driven over by steam distillation
separated from the water and agitated with dilute bydrochloric acid. The ortho-
nitro-toluol which remains undissolved is drawn off and distilled. It boils within
two or three degrees. On treatment with caustic soda the solution yields

page_text: toluidine very rich in para-toluidine and from which the para-toluidine can be
separated by cooling and centrifugating..
Dated this 5th day of November 1895.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.
UUMI LEIE DI MULTIVATION.
Improvements in the Treatment of Technióal Nitrotoluene.
We, ARTHUR GEORGE GREEN, F.C.S., F.I.C., of 13 Kings Drive, Heaton
Moor, near Stockport, Consulting Chemist, and HANS BENFEY, Doctor of
Philosophy, late of 51, now of 49 Nelson Street, Oxford Road, Manchester,
Chemist, both in the County of Lancaster, do hereby declare the nature of this
invention and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement :-
No satisfactory method is as yet known for the complete separation of the ortho-
and para-nitrotoluenes contained in the mixture of these isomers obtained by
nitration of toluol. The methods at present in use for separating these nitro
compounds or the corresponding toluidines (obtained by reducing the mixture) are
slow, troublesome, and costly, and the object of the present invention, is to provide
means for effecting the said separation in a quicker, less troublesome, and more
economical manner than hitherto, the ortho-nitro-toluene being obtained in a
practically pure state, whilst the para-isomer is obtained in the form of para-
toluidine.
It has long been known that the nitro-hydrocarbons can be reduced to the
corresponding amines by treatment with alkaline sulphides and it was by this
method that aniline was first obtained from nitro-benzol by Zinin (Journal für
Practische Chemie [1842] 27-149). Sodium and ammonium sulphides have
since been often employed for the reduction of nitro compounds, especially in
cases where it has been required to reduce one nitro-group in a compound without
effecting the reduction of another reducible group.
We have discovered that when mixtures of isomeric nitro-compounds are treated
with certain sulphides a differential action is exerted upon the separate com-
ponents. Thus, by the action of the sulphides of the alkalies, or of the alkaline
earths, upon mixtures of para and ortho nitro-toluene, the para-nitro toluene is
reduced more readily and rapidly than is the ortho-nitro-toluene. Upon this
observation we base the new method of separating these isomers, which forms the
subject matter of the present invention and which may be termed "fractional
reduction."
In carrying out our invention the mixture of nitro-toluenes is treated with a
suitable sulphide in amount rather more than is sufficient to reduce the whole of
the para-nitro-toluene present. A toluidine, very rich in the para-isomer, is thus
obtained, whilst the greater part of the ortho-nitro-toluene remains unreduced.
Any sulphide or hydrosulphide of the alkalies, or of the alkaline earths, may be
employed, such, for example, as the sulphides and hydro-sulphides of sodium,
potassium, calcium, strontiuu, barium, and the like, the "alkali-waste" of the
Le Blanc soda process being eminently, adapted for the purpose.
The following is an example of the manner in which our invention can be
carried into effect, but we do not limit ourselves to the exact details given
therein.
200 lbs. of commercial nitro-toluene (such as can be obtained by nitration of
toluol in the ordinary, manner), 400 lbs. of "alkali waste;" and a quantity of water
(dependent upon the amount of moisture contained in; such waste), say, 40 gallons
of water, are heated together for 12 hours or thereabouts in a vessel provided

page_text: with a stirrer and cohobator. The toluidine and unaltered nitro-toluene are then
driven over by steam distillation. The oil is separated from the water and
agitated with dilute hydrochloric acid. The ortho-nitro-toluene, which remains
undissolved, is drawn off and distilled. It boils within two or three degrees. On
treatment with caustic soda, the acid solution yields toluidine very rich in para-
toluidine, and from this, the para-toluidine can be separated by cooling and
centrifugating.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1. The separation of the ortho and para-isomers contained in technical nitro-
toluene by "fractional reduction" by means of a sulphide or a hydro-sulphide of
the alkalies, or of the alkaline earths, whereby the para-isomer is obtained for
the most part as para-toluidine, which is removed from the ortho-nitro-toluene
(which remains for the most part unattacked) by extraction by acids.
2. The preparation of para-toluidine from technical nitrotoluene by "fractional
reduction" by means of a sulphide or a hydro-sulphide of the alkalies or of the
alkaline earths, and extraction by dilute acids of the oil obtained, whereby the
para-toluidine passes into solution, and can be obtained by rendering the solution
alkaline and purifying.
دو
3. The preparation of ortho-nitro-toluene from technical nitro-toluene by
"fractional reduction by means of a sulphide or a hydro-sulphide of the
alkalies, or of the alkaline earths, extraction of the product with dilute acids, and
rectification of the undissolved oil.
4. The special method of carrying out the aforesaid processes by the employ-
ment of the so-called "alkali-waste" of the Le Blanc soda process as described in
the foregoing example.
Dated this 18th dor of Jul, 1896
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.