Manufacture of Ionone from Citral and Acetone and of Cyclocitral as Intermediate Product.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Manufacture of Ionone from Citral and Acetone and of Cyclocitral as
Intermediate Product.
I, ADOLF STREBEL, of 4211 Dreieckstrasse, Frankfurt a/Main, in the Empire
of Germany, Apothecary, do hereby declare the nature of this invention to be as
follows:-
According to the method of the English Patent Specification No. 8736 of the
year 1893, alkaline agents condense citral with acetone forming pseudoionone,
the latter being converted into the isoméric ionone by the action of acids. Theo-
retically it should be possible to proceed in the reverse manner to produce ionone,
by first preparing cyclocitral and condensing this with acetone to ionone, using
alkaline agents according to known methods.
By my invention I have found and proved that this method is also practicable,
and that in order to obtain a crude cyclocitral suitable for the preparation
of ionone in the manner described, the following method may be used.
Citral is condensed with cyanacetic acid or one of its salts or ethers, yielding
citralidenecyanacetic acid or a derivative of this compound; the citralidene-
cyanacetic acid or its derivative is then converted into the corresponding isomeric
cyclic compound by the method described in the English Patent Specification
No. 22114 of the year 1893, and the crude product thus obtained is treated at a
sufficiently high temperature with caustic alkali either alone or in presence of a
gentle oxidising agent.
The oil thus liberated is either submitted directly to alkaline condensation
with acetone, or, after fractional distillation, the portion of crude cyclocitral,
which boils at 80°-110° C. under a pressure of 15 in.m. is treated in this
manner.
The ionone thus produced is submitted to fractional distillation and further
purified by known methods.
The details of procedure are demonstrated in the following examples.
EXAMPLE I.
100 parts of cyanacetic acid dissolved in 300 parts of water are treated with a
solution of 80 parts of caustic soda in 200 parts of water, and subsequently with
a mixture of 180 parts of citral and 100 parts of alcohol. The liquid which is
turbid in the beginning becomes clear when agitated for a short period, its
temperature rising simultaneously. On acidification, citralidenecyanacetic acid
separates first as an oil, which gradually solidifies in crystalline form. It can be
used without further purification. The solidified citralidenecyanacetic acid is

page_text: obtained on recrystallization from a cold mixture of benzene and petroleum in
white crystals melting at 1210-122° C.
EXAMPLE II.
The crude solidified citralidenecyanacetic acid is converted into the corre-
sponding cyclic isomeride on being boiled in a reflux apparatus during about
12 hours with a solution of 80 parts by volume of concentrated sulphuric acid in
600 parts by volume of water. The neutral by-products which are formed at the
same time are separated by dissolving the crude acid in caustic lye, and extracting
the alkaline solution with ether. The cylic citralidenecyanacetic acid precipitated
from the alkaline liquid by acids forms a viscous syrup, and has not been hitherto
obtained in a crystalline form.
In order to split off cyclocitral from the cyclocitralidenecyanacetic acid, the
crude acid obtained from 180 parts of citral is dissolved in a small quantity of
caustic alkali, and treated with a powerful current of steam in a distillation
apparatus, 200 parts of caustic potash dissolved in a small quantity of water
being allowed to drop into the liquid meanwhile. The oil which distils over
contains the cyclocitral which is formed. The fraction of this oil which boils
at 80°-110° C. under a pressure of 15 m.m. is a yellowish liquid rich in cyclo-
citral, as has been proved by its conversion into ionone.
The separation of cyclocitral from cyclocitralidenecyanacetic acid can be also
effected by boiling the cyclocitralidenecyanacetic acid obtained from 180 parts of
citral with a solution of 200 parts of caustic potash in 300 parts
of water, and 300 parts of xylene for 10-12 hours in a reflux
apparatus, the layer of xylene being collected, dried and fractionated
under reduced pressure, when the fraction which boils at 80°-110° C. under a
pressure of 15 m.m. is collected as cyclocitral.
In order to facilitate the elimination of cyclocitral, a small quantity of a gentle
oxidising agent such as lead peroxide, manganese peroxide, barium peroxide,
sodium peroxide, or the like may be used in both cases.
EXAMPLE III.
The condensation of cyclocitral with acetone to ionone may be effected with
almost the same result by different alkaline agents. A good result is obtained for
instance by adding a solution of 5 parts of sodium in a small quantity of alcohol
to a mixture of 50 parts of crude cyclocitral and 100 parts of acetone, and allowing
the clear liquid to remain for about three hours at ordinary temperatures.
The product is neutralized with tartaric or another acid; the ionone thus set free
is distilled in a strong current of steam and submitted to fractional distillation
under reduced pressure, the fraction which boils at 1300-140° C. under a pressure
of 16 m.m. being collected as ionone.
The ionone when sufficiently purified by fractionation has the specific
gravity 0.9435 at 21° C. and is rich in the modification of ionone described as
ẞ-ionone.
When treated with an alcoholic solution of semicarbazide hydrochloride in
aqueous sodium acetate, the ionone prepared from cyclocitral yields a considera-
able proportion of ẞ-ionone-semi-carbazone melting at 148° C.
Ionone set free in the usual way from the crystallized semicarbazone yields
the parabromophenylhydrazone melting at 1160 which is characteristic for
B-ionone, when treated with parabromophenyl-hydrazine dissolved in acetic acid.
Dated this 4th day of November 1898.
ABEL & IMRAY,
Agents for the Applicant.

page_text: Manufacture of Ionone from Citral and Acetone and of Cyclocitral as
Intermediate Product.
I, ADOLF STREBEL, of 4211 Dreieckstrasse, Frankfurt a/Main, in the Empire
of Germany, Apothecary, 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:-
According to the method of the English Patent Specification No. 8736 of the
year 1893, alkaline agents condense citral with acetone forming pseudoionone,
the latter being converted into the isomeric ionone by the action of acids. Theo-
retically it should be possible to proceed in the reverse manner to produce ionone,
by first preparing cyclocitral and condensing this with acetone to ionone, using
alkaline agents according to known methods.
By my invention I have found and proved that this method is also practicable,
and that in order to obtain a crude cyclocitral suitable for the preparation
of ionone in the manner described, the following method may be used.
Citral is condensed with cyanacetic acid or one of its salts or ethers, yielding
citralidenecyanacetic acid or a derivative of this compound, the citralidene-
cyanacetic acid or its derivative is then converted into the corresponding isomeric
cyclic compound by the method described in the English Patent Specification
No. 22114 of the year 1893, and the crude product thus obtained is treated at a
sufficiently high temperature with caustic alkali either alone or in presence of a
gentle oxidising agent. The oil thus liberated is either submitted directly to
alkaline condensation with acetone, or, after fractional distillation, the portion of
crude cyclocitral, which boils at 800-110° C. under a pressure of 15 m.m. is
treated in this manner.
The ionone thus produced is submitted to fractional distillation and further
purified by known methods.
The details of procedure are demonstrated in the following examples.
EXAMPLE I.
100 parts of cyanacetic acid dissolved in 300 parts of water are treated with a
solution of 80 parts of caustic soda in 200 parts of water, and, subsequently with
a mixture of 180 parts of citral and 100 parts of alcohol. The liquid which is
turbid in the beginning becomes clear when agitated for a short period, its
temperature rising simultaneously. On acidification, citralidenecyanacetic acid
separates first as an oil, which gradually solidifies in crystalline form. It can be
used without further purification. The solidified citralidenecyanacetic acid is
obtained on recrystallization from a cold mixture of benzene and petroleum in
white crystals melting at 121°—122° C.
EXAMPLE II.
The crude solidified citralidenecyanacetic acid is converted into the corre-
sponding cyclic isomeride on being boiled in a reflux apparatus during about
12 hours with a solution of 80 parts by volume of concentrated sulphuric acid in
600 parts by volume of water. The neutral by-products which are formed at the
same time are separated by dissolving the crude acid in caustic lye, and extracting
the alkaline solution with ether. The cylic citralidenecyanacetic acid precipitated
from the alkaline liquid by acids forms a viscous syrup, and has not been hitherto
obtained in a crystalline form.
In order to split off cyclocitral from the cyclocitralidenecyanacetic acid, the

page_text: crude acid obtained from 180 parts of citral is dissolved in a small quantity of
caustic alkali, and treated with a powerful current of steam in a distillation
apparatus, 200 parts of caustic potash dissolved in a small quantity of water
being allowed to drop into the liquid meanwhile. The oil which distils over
contains. the cyclocitral which is formed.
The fraction of this oil which boils at 80°-110° C. under a pressure of 15 m.m.
is a yellowish liquid rich in cyclocitral, as has been proved by its conversion into
ionone.
The separation of cyclocitral from cyclocitralidenecyanacetic acid can be also
effected by boiling the cyclocitralidenecyanacetic acid obtained from 180 parts of
citral with a solution of 200 parts of caustic potash in 300 parts
of water, and 300 parts of xylene for 10-12 hours in a reflux
apparatus, the layer of xylene being collected, dried and fractionated
under reduced pressure, when the fraction which boils at 80°--110° C. under a
pressure of 15 m.m. is collected as cyclocitral.
In order to facilitate the elimination of cyclocitral, a small quantity of a gentle
oxidising agent such as leail peroxide, manganese peroxide, barium peroxide,
sodium peroxide, or the like may be used in both cases.
EXAMPLE III.
The condensation of cyclocitral with acetone to ionone may be effected with
almost the same result by different alkaline agents. A good result is obtained for
instance by adding a solution of 5 parts of sodium in a small quantity of alcohol
to a mixture of 50 parts of crude cyclocitral and 100 parts of acetone, and allowing
the clear liquid to remain for about three hours at ordinary temperatures.
The product is neutralized with tartaric or another acid; the ionone thus set free
is distilled in a strong current of steam and submitted to fractional distillation
under reduced pressure, the fraction which boils at 1300-140° C. under a pressure
of 16 m.m. being collected as ionone.
The ionone when sufficiently purified by fractionation has the specific
gravity 0.9435 at 21° C. and is rich in the modification of ionone described as
ẞ-ionone.
When treated with an alcoholic solution of semicarbazide hydrochloride in
aqueous sodium acetate, the ionone prepared from cyclocitral yields a considera-
able proportion of ẞ-ionone-semi-carbazone melting at 148° C.
Ionone set free in the usual way from the crystallised semicarbazone yields
the parabromophenylhydrazone melting at 116° C. which is characteristic for
ẞ-ionone, when treated with parabromophenyl-hydrazine dissolved in acetic acid.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:
1. The herein described process for preparing ionone from citral and acetone
employing cyclocitral as intermediate product, by condensing citral with
cyanacetic acid to citralidenecyanacetic acid, converting this into the correspond-
ing cyclic isomeric acid by the method described in the Specification No. 22,114
of 1893, splitting off crude cyclocitral by acting on the product with caustic alkali
alone or in presence of a gentle oxidising agent and condensing cyclocitral with
acetone to ionone by means of an alkaline agent.
2. The herein described manufacture of citralidenecyanacetic acid by condens-
ing citral with cyanacetic acid or a salt or ether of this acid by means of an
alkaline agent to cytralidene cyanacetic acid or one of its derivatives.
3. The herein described manufacture of cyclocitral by condensing citral with
cyanacetic acid to citralidenecyanacetic acid according to Claim 2, converting this
substance into the corresponding cyclic isomeric acid by the method described in
the Specification No. 22,114 of 1893 and splitting off cyclocitral from the product
by caustic alkali alone or in presence of a gentle oxidising agent.

page_text: 4. The herein described manufacture of ionone from the cyclocitral obtained
according to Claim 3 and acetone, by condensing these two substances by means of
an alkaline agent.
5. Citralidenecyanacetic acid manufactured as above described by the alkaline
condensation of citral and cyanacetic acid and having a melting point
about 121° C. when in a pure state.
6. Crude cyclocitral split off from cyclocitralidenecyanacetic acid as above
described and having a boiling point of 80° to 110° C. under a pressure of
15 m.m.
1 1
1
1000