Method for Oxydation of Ortho-toluol-sulphamide to Saccharine, by Avoiding the Formation of Ortho-toluol-sulpho-acid or Ortho- sulpho-benzoic-acid.
Year: 1898

page_text: Date of Application, 14th Feb., 1898
Complete Specification Left, 11th Nov., 1898-Accepted, 14th Jan., 1899
PROVISIONAL SPECIFICATION.
Method for Oxydation of Ortho-toluol-sulphamide to Saccharine, by
Avoiding the Formation of Ortho-toluol-sulpho-acid or Ortho-
sulpho-benzoic-acid.
I, JULIUS HAUFF, of Feuerbach, near Stuttgart, Germany, Manufacturer, do hereby
declare the nature of this invention to be as follows :-
The object of this invention is a method for oxydation of ortho-toluol-sulphamide
to saccharine by avoiding the formation of ortho-toluol-sulpho-acid or ortho-sulpho-
benzoic-acid.
In the German Patent No. 35211 of Fahlberg and List it is stated under 4./
Oxydation of amide to benzoic acid sulphinide "Investigators formerly supposed that
this oxydation could only take place in an alkaline solution, and always remarked as
a bye-product the formation of large quantities of ortho-sulpho-benzoic-acid. But
it has now been discovered that the formation of sulpho-benzoic-acid can be entirely
avoided if during the oxydation, the mixture is always kept neutral with perman-
ganate of potassium. The formation of sulpho-benzoic-acid is only effected out of
sulpho-benzamine-acid under the influence of free alkali and separation of ammonia."
This theory might be correct if a large formation of saccharine really took place
when the precautions therein prescribed were observed. But if the work is carried
on exactly according to the prescribed method, that is if the formation of free alkali
is prevented by the addition of suitable ingredients, no saccharine is formed. But
on the other hand saccharine is formed in almost fabulous quantity if the amide is
previously dissolved in lye and the free alkali which forms during oxydation is not
neutralised.
There is reason to suppose that the amide combines with the alkali to make a
combination of the following composition.

page_text: toluol-sulphon-amide, the imide group comes under the protection of the metal atom
and immediately in the oxydation of the methyl group to the carboxyl group by
interior anhydride formation forms the salt of the saccharine. A further confirmation
is, that in an alkaline solution the theoretical quantity of hyper-manganate of potash
is nearly sufficient.
Hyper-manganate of potash
Water
-
77 kg.
600 ltr.
The solution of hyper-manganate of potash is allowed to flow slowly into the
solution of amide at a temperature of about 70° and the mixture is stirred until it
changes colour. The saccharine will be separated in the usual manner.
The yield is 26-28 kg. therefore 80-90% of the theory. As the yield of
saccharine by oxydation of amide is the most important factor in determining its
price the above yield constitutes a very considerable advance in the saccharine manu-
facture.
Method for Oxydation of Ortho-toluol-sulphamide' to Saccharine, by
Avoiding the Formation of Ortho-toluol-sulpho-acid or Ortho-
sulpho-benzoic-acid.
I, JULIUS HAUFF, of Feuerbach, near Stuttgart, Germany, Manufacturer, 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 :—
The object of this invention is a method for oxy-dizing ortho-toluol-sulphamide to
saccharine by avoiding the back formation of ortho-toluol-sulpho-acid or ortho-
sulpho-benzoic-acid.
In the German Patent No. 35211 of Fahlberg and List, it is stated under 4./
Oxydation of amide to benzoic acid sulphinide: "The inventors formerly supposed
that this oxydation could only be effected in an alkaline solution, and they always
remarked the formation of large quantities of ortho-sulpho-benzoic-acid as a by-
product. But the inventors have now discovered that the formation of sulpho-
benzoic-acid can be entirely avoided if during the oxydation with permanganate of
potash, the oxydizing mixture is always kept neutral. The formation of sulpho-
benzoic-acid is only effected out of sulpho-benzamine-acid under the influence of free
alkali and under separation of ammonia."
This theory might be correct if a quantitative formation of saccharine really took
place when the precautions therein prescribed were observed.
But if the work is carried on exactly according to the prescribed method, that is,
if the formation of free alkali is prevented by the addition of suitable ingredients, no
saccharine is formed.
But on the other hand, saccharine is formed in almost theoretical quantity, if the

page_text: amide is previously dissolved in potash- or soda-lye, and the free alkali formed during
the oxydation is not neutralised.
There is reason to suppose that the amide combines with the alkali to a com-
bination of the following composition:
"
C.H
'CH
SO₂NHNa
In this combination I have the imide group NH, which is constant against
oxydizing agents, while the amido group is easily oxydized away. Therein lies the
cause of the back formation of toluol-sulpho-acid and afterwards of sulpho-benzoic-
acid. This is further proved by the fact, that for the oxydation of ortho-toluol-
sulphon-amide to otho-sulpho-benzoic-acid more than double the theoretic quantity
of permanganate of potash is used, which it would be impossible to use if the alkali
formed in the oxydation should simply separate the amido group.
These considerations are further supported by the fact, that neither the ortho-toluol-
sulphon-amide nor the saccharine itself undergoes any change by the concentrations
of the free alkali which separates out of the permanganate of potash.
It is therefore solely the influence of the oxydation in a neutral solution whereby
the amido group is oxydized away, while in the alkaline solution of the ortho-toluol-
sulphon-amide, the imide group is maintained under the protection of the metal
atom, and forms immediately in the oxydation of the methyl group to the carboxyl
group, by interior anhydride formation the salt of the saccharine. This is confirmed
by the fact that in an alkaline solution the theoretical quantity of permanganate of
potash is nearly sufficient.
Water
600 ltr.
The solution of permanganate of potash is allowed to flow slowly into the solution
of the amide at a temperature of about 70° and the mixture is stirred until the
colour is disappeared. The saccharine will be separated in the usual manner.
The yield is 26-28 kg. therefore 80-90% of the theory. As the yield of
saccharine by the oxydation of the amide is the most important factor in determining
its price, the above yield constitutes a very considerable advance in the saccharine
manufacture.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed I declare that what I
claim is:-
The method for oxydizing ortho-toluol-sulphamide to saccharine by avoiding the
back formation of ortho-toluol-sulpho-acid or ortho-sulpho-benzoic-acid substantially
as described.
The 11th day of November 1898.
H. GARDNER,
Patent Agent, 166, Fleet Street, London,
Agent for the said Julius Hauff.