Improvements in the Manufacture of Vanilline.
Year: 1896

page_text: Date of Application, 11th Apr., 1896-Accepted, 16th May, 1896
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Vanilline.
I, OTTO PREU, of No. 16 Währingerstrasse, Vienna IX, in the Empire of
Austria, Chemist, do hereby declare the nature of my said invention and in what
manner the same is to be performed, to be particularly described and ascertained in
and by the following statement :-
It is a well known fact that the hydroxyl group of the eugenol and the iso-
eugenol is protected from decomposition by an acid or an alcohol radical. If, now,
vanilline be prepared from eugenol or iso-eugenol by oxidising with potassium
permanganate or chromic acid, a drawback must be contended with viz., the
oxidation is very difficult to control.
Vanillic acid and vanilloyl carbonic acid very readily form such compounds
necessitating the employment of a complicated method for their separation.
If the usual methods of oxidation are employed eugenol, in particular, gives
but a very small yield of vanilline, unless it be previously converted into iso-
eugenol.
The process described below, allows of the ready preparation of vanilline from
eugenol or oil of cloves, which can be easily obtained commercially, without
previously converting eugenol into iso-eugenol; iso-eugenol, however, gives the
best results.
The hydrogen of the hydroxyl group in the eugenol or the iso-eugenol is at
first replaced by the radical of an organic acid, for instance, that of acetic acid,
propionic acid, butyric acid, valerianic acid, benzoic acid etc., or by the radical of
anorganic acids by the action of sulphuryl chloride, thionyl chloride, phosphorus
oxychloride on the alkaline solution of eugenol or iso-eugenol.
Or the hydrogen can be replaced by the radical of an alcohol by means of benzyl
chloride.
Monomolecular acid derivatives such as chromyl chloride, CrO,Cl, are
preferably employed for acting on those derivatives, whereby a precipitate of
chocolate brown colour is produced, which precipitate on being decomposed by
water, yields vanillic ether of the corresponding class; such vanillic ether on being
saponified, yields in turn vanilline in copious quantities.
The process is carried out as follows:-
One molecule of for instance, acetyl-eugenol or acetyl-iso-eugenol, is dissolved
in five times its bulk of a dissolving agent, say, bisulphide of carbon or chloro-
form. Two molecules of chromyl chloride, which have also been previously
diluted with five times its bulk of the very same dissolving agent (sulphide of
carbon or chloroform) are then gradually added, care being taken that the tempera-
ture never rises above 40° C.; this is effected either by cooling, or by slowly
adding the chromyl chloride.
The mass is allowed to stand over night, filtered and the dissolving agent sucked
off. The precipitate, which is still in a moist state, is worked up according to any
of the following methods.
1. The precipitate is dried on a water-bath at about 50° Centigrade by
evaporating the dissolving agent in excess, and the dry light brown precipitate,
which is very hygroscopic, is put into about six to ten times the weight of water.
The precipitate is thus decomposed and an oily resinous mass containing acetyl
vanilline precipitates in large quantities at the bottom.

page_text: After separating said mass, the latter is saponified by warming on a water bath
for several hours with a small excess of sodium or potassium hydrate. The mass
is allowed to cool and then acidified with dilute sulphuric acid, whereby a resinous
mass is produced, which contains the vanilline and from which such vanilline is
isolated by shaking the mass with a solvent, such as ether. The vanilline is
obtained from the etheric solution by combining it with an alkaline bisulphite,
from which compound, the vanilline is finally separated by decomposing it with
dilute sulphuric acid. The crude vanilline is purified in the usual manner.
2. The precipitate while still moist is decomposed without sucking off the
solvent, by digesting it with six to ten times its weight of water, whereby the oily
resinous mass separates along with the solvent employ ed. From that mass, which
is in a very liquid state, and which is even diluted if necessary the acetyl vanilline
is isolated by shaking with bisulphite. The acetyl compound is saponified and
purified as usual.
3. After the solvent has been well sucked from the precipitate, the latter is
decomposed by water and saponified on the water bath, as described in method
No. 1. The remaining solvent is thus driven out and the procedure followed up
in the same manner set forth in No. 1.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed 1 declare that what I
claim is :
Improvements in the manufacture of vanilline by treating eugenol or iso-eugenol
or its derivatives respectively, with chromyl-chloride, substantially as described.
Dated this 11th day of April 1896
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant.