IMPROVEMENTS IN THE PREPARATION OF CINNAMIC ACID AND OF ITS SUBSTITUTION PRODUCTS
Year: 1880

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields, in the
County of Middlesex, Gentleman, for an Invention of "IMPROVEMENTS IN
THE PREPARATION OF CINNAMIC ACID AND OF ITS SUBSTITUTION PRODUCTS."
A communication from abroad by Heinrich Caro, of Mannheim, in the Empire
of Germany, Chemist to the Badische Anilin and Soda Fabrik, of Mannheim
aforesaid (Grand Duchy of Baden).
PROVISIONAL SPECIFICATION left by the said John Henry Johnson at the
Office of the Commissioners of Patents on the 17th August 1880.
JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of
Middlesex, Gentleman. "IMPROVEMENTS IN THE PREPARATION OF CINNAMIC
ACID AND OF ITS SUBSTITUTION PRODUCTS." A communication from abroad by
Heinrich Caro, of Mannheim, in the Empire of Germany, Chemist to the Badische
Anilin and Soda Fabrik, of Mannheim aforesaid (Grand Duchy of Baden).
The
Cinnamic acid as is well known inay be synthetically prepared from benzoic
aldehyde by the action of acetic anhydride in presence of a metallic acetate. Now
this Invention consists in dispensing with the use of both the benzoic aldehyde
and the acetic anhydride by employing mixtures containing dichloride. of benzylene
C, H, CH A., and a metallic acetate, by preference, dry acetate of sodium.
said mixtures are heated to a temperature of, say, from about about 180 to 200
degree centigrade, and the action is allowed to proceed until the cinnamic acid thus
produced no longer increases in quantity. The separation of the cinnamic acid
may then be effected in various ways, such, for instance, as by first adding an
excess of alkali to the product of the reaction, and then submitting the same to a
distillation with steam in order to remove the volatile bye-products, and to obtain
a. solution of an alkaline cinnamate, from which, after filtration, cinnamic acid may
be precipitated by means of a stronger acid, such, for example, as hydro chloric acid.
In some instances I however prefer to boil down the alkaline solution until the

page_text: alkaline cinnamate separates out, and it may, after cooling, be filtered off, its mother
liquor containing the excess of unemployed acetate which may thus be recovered.
The alkaline cinnamate is afterwards dissolved in water and decomposed by a
stronger acid. Instead of the dichloride of benzylene above named I may also
employ the corresponding dibromide of benzylene, or the corresponding chloro-
brominated compound C, H, CH, Br A, or any mixtures, containing the said
products.
The substitution-products of cinnamic acid, such as contain one or more atoms of
chlorine bromine, or of the nitro-group NO, in their benzene-residue may be
prepared in an analogous manner by heating metallic acetates, and by preference,
dry sodium acetate with the corresponding chlorine-bromine or nitro substitution-
products of the above mentioned chloride bromide or chloro-bromide of benzylene.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Henry Johnson in the Great Seal Patent Office on the 16th
February 1881.
JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman. "IMPROVEMENTS IN THE PREPARATION OF CINNAMIC ACID AND OF
ITS SUBSTITUTION PRODUCTS." A communication from abroad by Heinrich Caro,
of Mannheim, in the Empire of Germany, Chemist to the Badische Anilin and Soda
Fabrik, of Mannheim aforesaid (Grand Duchy of Baden).
Cinnamic acid, as is well known, may be synthetically prepared from benzoic
aldehyde by the action of acetic anhydride in presence of a metallic acetate.
Now this Invention consists in dispensing with the use of both the benzoic
aldehyde and the acetic anhydride, by employing mixtures containing dichloride
of benzylene C, H, CH C₂, and dry acetate of sodium.
In order to carry out the said Invention I proceed as follows:-
About one part by weight of pure or commercial dichloride of benzylene and
about two parts by weight of dry acetate of sodium are intimately mixed and
heated to a temperature of, say, from about 180 to 200 degrees centigrade for
about 18 to 20 hours.
The apparatus in which I conduct the said process may be a closed pressure-
vessel made of cast iron or of any other suitable metal, and capable of resisting an
internal pressure of about ten atmospheres, but by preference I employ a cast iron
still provided with an agitator and with a condensing arrangement which allows
the condensed vapours to run back into the still. The said vessel or still is placed
in an air-bath or in an oil bath, and the heat is to be carefully regulated so as not
to allow the temperature of the above mentioned mixture to rise considerably
above two hundred degrees centigrade, nor to sink considerably below one hundred
and eighty degrees centigrade, as above mentioned. In practice the formation of
cinnamic acid has been found to be complete after about eighteen or twenty hours,
as above mentioned, but the exact duration of the process may be arrived at by
with-drawing a sample of the mixture from time to time and ascertaining the
amount of cinnamic acid contained in the same. The action is allowed to proceed
until the cinnamic acid thus produced no longer increases in quantity.
The separation of the cinnamic acid from the crude product or melt thus obtained
may then be effected in various ways. In every instance I first add about forty
parts of water and about one part by weight of caustic soda solution of about 1.37
specific gravity, or as much of the said alkali as is necessary to render the moisture
of a strongly alkaline reaction. I then submit the said alkaline mixture to a
distillation with steam in order to remove any volatile bye-products which may be
contained therein. The residue is then filtered, and from the solution of cinnamate
of sodium thus obtained cinnamic acid may be precipitated by means of a stronger
acid, such, for example, as hydrochloric acid. The precipitated acid is then collected
on a filter, washed, and dried, or it may be further purified by distillation, or by
crystallisation from water, or from alcohol, or from any other suitable solvent.
According to another method, and which I prefer to employ, the alkaline solution
of cinnamate of sodium, obtained as above described, may be boiled down or
concentrated until the alkaline cinnamate separates out. The mixture is then
allowed to cool, and the precipitate of cinnamate of sodium thus produced is filtered,
pressed, and then redissolved in water. The solution thus obtained is then decomposed
by a stronger acid, and the cinnamic acid thus set free is filtered, washed, and dried,
or further purified as above described.
The alkaline filtrate from which the cinnamate of sodium has been separated as
above described may then be further evaporated until the chloride of sodium

page_text: contained therein has separated out, or nearly so. The remaining mother-liquor
contains the excess of acetate of sodium employed in the above process, and which
may thus be recovered. For this purpose I allow the said mother-liquor to
crystallize, and the crystallized or hydrated acetate of sodium thus obtained may
afterwards be dehydrated in order to produce dry acetate of sodium suitable for
renewed application in the above described process for the preparation of cinnamic
acid.
Instead of the dichloride of benzylene above named I may also employ the
corresponding dibramide of benzylene C, H, CH, B, or the corresponding
chloro-brominated compound C, H, CH, Br, Cl.
In an analogous manner the substitution products of cinnamic acid, such as
contain chlorine, bromine, or the nitro-group NO₂, in their benzine residue may be
prepared by heating dry sodium acetate with the corresponding chlorine-bromine
or nitro-substitution products of the above mentioned dichloride, dibromide, or
chloro-bromide of benzylene.
As an example I take about one part by weight of dichloride of chlorobenzylene
C, H., C, CH, Cl, and heat the same with about two parts by weight of dry acetate
of sodium to a temperature of, say, from about 180 to 200 degrees centigrade for
about twelve hours, and in the manner above described. The product of, the reaction
contains chlorocinnamic acid, which may then be separated by any of the methods
before described for the separation of cinnamic acid. In an analogous manner I
obtain bromocinnamic acid from dichloride of bromo-benzylene C, H, Br, CH, C.,
or nitrocinnamic acid from dichloride of nitro-benzylene C, H, NO, CH Cl..
In the above described process I may also employ dry acetate of potassium, or a
mixture of the dry acctates of potassium and sodium in place of the dry acetate of
sodium therein mentioned, but in practice I have found the dry acetate of sodium
to produce the best results in point of economy.
Having now described and particularly ascertained the nature of the said
Invention, and the manner in which the same is or may be used or carried into effect,
I would observe in conclusion that what I consider to be novel and original, and
therefore claim as the Invention secured to me by the hereinbefore in part recited
Letters Patent is,-
First. The preparation of cinnamic acid by the action of dry acetate of sodium
(or its equivalent, as herein set forth) upon dichloride of benzylene or upon
the corresponding brominated or chlorobrominated compounds of benzylene,
substantially in the manner hereinbefore described.
Second. The preparation of substitution products of cinnamic acid, such as
contain chlorine, bromine, or the nitro-group in their benzene-residue, by the action
of dry acetate of sodium (or its equivalent as herein set forth) upon the corresponding
chlorine-bromine or nitro-substitution products of dichloryde of benzylene, or of the
corresponding brominated or chlorobrominated compounds of benzylene, substantially
in the manner hereinbefore described.
In witness whereof, I, the said John Henry Johnson, have to this my
Specification set my hand and seal, the Sixteenth day of February, One
thousand eight hundred and eighty one,
J. HENRY JOHNSON. (L.S.)