Year: 1893

page_text: Date of Application, 11th Mar., 1893
Complete Specification Left, 9th Dec., 1893-Accepted, 13th Jan., 1894

page_text: varied, without altering thereby the nature of this invention, which relates to the
production of piperazine, or its salts, by heating dinitrosodiphenyl piperazine, or
the analogues or homologues thereof, with acids.
Dated this 11th dow of March 1802
NEWTON & SON,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Piperazine and its Salts.
I, HENRY EDWARD NEWTON, of The Office for Patents, 6 Bream's Buildings,
Chancery Lane in the County of London, Patent Agent, 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 :——
My foreign correspondents have described in the Specification of Letters
Patent No. 4497, dated 7th March 1892, a process for producing piperazine by
treating dinitrodiphenyl piperazine with sulphurous acid, or salts thereof.
The present invention relates to a new process for producing piperazine.
It is known from Möhlau's observations (see Berichte der Deutschen Chemischen
Gesellschaft, Volume XIX, page 2010), that when nitrosodimethylaniline is heated
with muriatic acid, it affords a mixture of dimethylparaphenylenediamine,
dimethylparadichloroparadiphenylene diamine, and paradichloroparaphenylene
diamine.
My foreign correspondents have now found, that dinitrosodiphenyl piperazine
(first described by Morley in the Berichte der Deutschen Chemischen Gesellschaft,
Volume XII, page 1795), differs in this respect from nitrosodimethylaniline, as it
yields piperazine when subjected to the action of acids (other than sulphurous
acid).
In order to produce piperazine, or its salts, by this process, my foreign
correspondents generally proceed in the following manner, viz. they thoroughly
mix the freshly prepared paste of dinitrosodiphenyl piperazine with a suitable acid
(excluding sulphurous acid), and boil the resulting liquid mixture until the
dinitroso compound is totally decomposed.
Instead of preparing mixtures of dinitrosodiphenyl piperazine and dilute acids,
the acid solutious which are obtained on converting diphenyl piperazine into its
dinitroso derivative can be used with the same result. Piperazine or its salts
ere thus formed by boiling the said solutions until the desired decomposition has
taken place.
My foreign correspondents illustrate this new method of producing piperazine, or
its salts, by the following examples. The parts are by weight.
FIRST EXAMPLE.
1 part of a paste of dinitrosodiphenyl piperazine, containing 12 per cent. of the
dinitroso product, is mixed with 1 part of muriatic acid (20 degrees Baumé), and
30 parts of water, and this liquid is boiled during about two hours, the water which
escapes being replaced, if necessary. The liquid is filtered, and the filtrate is
mixed with a quantity of alkali, equivalent to the quantity of acid used; it is then
filtered from a small quantity of a precipitate, and a small excess of soda lye having
been added to the filtrate, the liquid is distilled from an oil bath. The distillate is
acidified with muriatic acid, and evaporated. By decomposing the piperazine
hydrochloride thus formed, with alkalies, and subsequently distilling, the piperazine
is obtained together with some water. This process affords a satisfactory yield of
piperazine or its hydrochloride.
My foreign correspondents have further found, that instead of the muriatic acid

page_text: used in the above example, other mineral acids can be used, such as sulphuric acid
or phosphoric acid. If the last-named acids are used, the corresponding salts.
of piperazine are first formed, from which piperazine may be separated in the usual
manner.
SECOND EXAMPLE.
1 part of diphenyl piperazine, dissolved in a mixture containing 700 parts of
water and 8-3 parts of muriatic acid (20 degrees Baumé), and 4.65 parts of
sulphuric acid (66 degrees Baumé), is converted into its dinitroso derivative by
adding 0.62 parts of sodium nitrite. The resulting liquid is filtered, in order
to remove small quantities of a resinous matter, and the filtrate is evaporated until
its volume is about of the original volume. During this operation, a black
precipitate separates, the originally bright greenish-yellow liquid assuming a dull
reddish color. (If a portion of the mixture be filtered, piperazine can be easily
detected in the filtrate). A quantity of calcium carbonate, or barium carbonate,
equivalent to the sulphuric acid employed, is then added to the mixture, without
previously filtering it. The calcium or barium sulphate having been separated, the
filtrate is boiled down to a small bulk, then mixed with soda, and the piperazine is
distilled off by means of steam.
The piperazine or its salts are obtained from the distillate in a suitable
manner.
My foreign correspondents, however, do not limit themselves to the mode of
working described in the above examples. The directions given therein can be
varied, without thereby altering the nature of this invention, which relates to the
production of piperazine, or its salts, by heating dinitroso diphenyl piperazine with
acids. The use of sulphurous acid for producing piperazine from dinitroso diphenyl
piperazine, as described in the Specification of Letters Patent No. 4497, dated
7th March 1892, is not claimed in this Specification.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me from
abroad, I declare that what I claim is :-
1. The production of piperazine or its salts by heating dinitrosodiphenyl
piperazine with suitable acids (excluding sulphurous acid), and isolating the
piperazine, either as such, or in the form of its salts.
2. The process for producing piperazine, which consists in boiling dinitrosodiphenyl
piperazine with muriatic, sulphuric, or phosphoric acid; filtering, neutralising the
filtrate with alkali, again filtering, adding alkali to the filtrate, distilling, and
isolating the piperazine from the distillate, either as such, or in the form of
its salts.
3. In the manufacture of piperazine, the process which consists in converting
diphenyl piperazine, by means of sodium nitrite or the like, in the presence of an
excess of acid, into dinitrosodiphenyl piperazine, boiling the resulting acid liquid or
mixture, neutralising, filtering, adding alkali to the filtrate, concentrating, distilling,
and isolating the piperazine from the distillate, either as such, or in the form of
its salts.
Dated this 7th day of December 1893.