Improvements in the Production of Aromatic Aldehydes.
Year: 1897

page_text: Date of Application, 27th Sept., 1897
Complete Specification Left. 27th June, 1898-Accepted, 27th Oct., 1898
Improvements in the Production of Aromatic Aldehydes.
A communication from abroad by LA SOCIÉTÉ CHIMIQUE DES USINES DU RHÔNE,
anciennement Gilliard, P. Monnet et Cartier, of Lyons, France, Manu-
facturers.
1, GEORGE BELOE ELLIS, of the Firm of J. C. Mewburn and Ellis, of 55 and 56,
Chancery Lane, in the County of London, Chartered Patent Agents, do hereby
declare the nature of this invention to be as follows;-
Hitherto the conversion of methyl derivatives of-the aromatic hydrocarbons into
aromatic aldehydes has been ordinarily effected in the following way, which may
be described as an indirect method:-
The CH, of the lateral chain has been converted by the action of chlorine
into X CH,Cl or X CHCI, and the aldehydes have been produced from these
chlorination products by subsequent oxidation.
I
Apart from the cost of chlorination this process has the drawback, that a certain
amount of chlorine or chlorinated products enters into the aromatic nucleus;
and the removal of these products generally presents difficulties. In some cases,
e.g. in the manufacture of benzaldehyde this drawback is not of much consequence,
but in others, e.g., in the manufacture of toluylic aldehydes it is very appreciable.
My foreign correspondents have discovered that aldehydes can be produced by
direct oxidation, if care is taken that the oxidizing agent is always in the presence
of a large excess of the CH, compound and this constitutes the characteristic
feature of the present invention. Hitherto the direct oxidation of the CH, of
aromatic compounds has practically always yielded carboxylic acids. By this,
simple expedient discovered by my foreign correspondents the further progress
of the oxidation, i.e., the formation of carboxylic acid can be almost completely
prevented.
The reaction which my correspondents have discovered is capable of general
application.
Up to the present my correspondents have obtained the best results by the use
of manganese binoxide and sulphuric acid as the oxidising agent. But according
to their experience other suitable oxidizing agents may also be employed, care
being always taken to have a large excess of the product to be oxidized at the close
of the reaction.
The following examples may serve to illustrate the method of application of
this new process of manufacture. The best yields have been obtained under the
conditions and with the proportions stated, but the conditions especially the con-
centration of the acid and the temperature may be varied within wide limits.
EXAMPLE 1.
Benzaldehyde. 300 kg. of toluol and 700 kg. of sulphuric acid of 65 % are
mixed together in an apparatus fitted with a stirring device, and 90 kg. of man-
ganese binoxide are slowly added in the form of a fine powder during vigorous
stirring The temperature is maintained at about 40° C. After all the binoxide

page_text: time in order to complete the reaction. The mixture of benzaldehyde and toluol
is then distilled with steam and the separation is effected in the well known
manner..
EXAMPLE 2.
Toluylaldehyde (o. m. p.). The xylenes are treated as stated in Example 1, at a
temperature of about 25°. The oxidation takes place more readily than in the
case of toluol.
The process of manufacture discovered by my correspondents can also be applied
to produce substituted aldehydes. For example orthochlorbenzaldehyde can be
easily produced by treating orthochlortoluene according to the method described
in Example 1.
A communication from LA SOCIÉTÉ CHIMIQUE DES USINES DU RHÔNE, ancienne-
ment Gilliard, P. Monnet et Cartier, of Lyons, France, Manufacturers.
I, GEORGE BELOE ELLIS, of the Firm of J. C. Mewburn and Ellis, of 55 and 56,
Chancery Lane, in the County of London, Chartered Patent Agents, do hereby
declare the nature of the said invention, and in what manner the same is to be
-performed, to be particularly described and ascertained in and by the following
statement:
Hitherto the conversion of methyl derivatives of the aromatic hydrocarbons into
aromatic aldehydes has been ordinarily effected in the following way, which may
be described as an indirect method;
The CH, of the lateral chain has been converted by the action of chlorine
into X CH,Cl or X-CHC₁₂, and the aldehydes have been produced from those
chlorination products by subsequent oxidation.
Apart from the cost of chlorination, this process has the drawback that a certain
amount of chlorine or chlorinated products enters into the aromatic nucleus:
and the removal of these products generally presents difficulties. In some cases,
c.g. in the manufacture of benzaldehyde, this drawback is not of much consequence,
but in others, e.g., in the manufacture of toluylic aldehydes it is very appreciable.
My foreign correspondents have discovered that aldehydes can be produced by
direct oxidation, if care is taken that the oxidizing agent is always in the presence
of a large excess of the CH, compound, and this constitutes the characteristic
feature of the present invention. Hitherto the direct oxidation of the CH, of
aromatic compounds has practically always yielded carboxylic acids. By this
simple expedient discovered by my foreign correspondents the further progress
of the oxidation, i.e., the formation of carboxylic acid can be almost completely
prevented.
The reaction which my foreign correspondents have discovered is capable of
general application.
Up to the present my correspondents have obtained the best results by the use
of freshly precipitated manganese binoxide or Weldon mud and sulphuric acid

page_text: as the oxidizing agent. But according to their experience other suitable oxidiz-
ing agents may also be employed, care being always taken to have a large excess
of the product to be oxidized at the close of the reaction.
The following examples may serve to illustrate the method of application of this
new process of manufacture. The best yields have been obtained under the con-
ditions and with the proportions stated, but the conditions, especially the concen-
tration of the acid and the temperature, may be varied within wide limits.
EXAMPLE 1,
Benzaldehyde. 300 kg. of toluol and 700 kg. of sulphuric acid of 65 % are
mixed together in an apparatus fitted with a stirring device, and 90 kg. of man-
ganese binoxide are slowly added in the form of a fine powder during vigorous
stirring. The temperature is maintained at about 40° C. After all the binoxide
of manganese has been added the stirring device is kept in operation for some
time in order to complete the reaction. The mixture of benzaldehyde and toluol
is then distilled with steam and the separation is effected in the well-known
manner,
EXAMPLE 2.
Toluyaldehyde (o-. m. p.). The xylenes are treated as stated in Example 1, at a
temperature of about 25°. The oxidation takes place more readily than in the
case of toluol.
The process of manufacture discovered by my correspondents can also be applied
to produce substituted aldehydes. For example orthochlorbenzaldehyde can be
easily produced by treating orthochlortoluene according to the method described
in Example 1.
Nitro derivatives of the hydrocarbons, such as nitrotoluene and nitroxylene
also yield the corresponding aldehydes. The behaviour of the hydroxyl deriva-
tives towards oxidizing agents under the above conditions varies; thus the methyl
ether of para-cresol gives an aldehyde without difficulty, whilst the ortho-cresol
compounds give no aldehyde under the same conditions.
Having now particularly described and ascertained the nature of the said
invention, as communicated to me, and in what manner the same is to be per-
formed, I declare that what I claim is :-
1. The process of manufacturing aromatic aldehydes by the direct oxidation
of the methyl group in aromatic hydrocarbons, as for example toluene or xylene,
or their substitution derivatives, (as for example chloro- or nitro-toluene), which
process consists in treating the said hydrocarbons or derivatives with an oxidizing
agent such as freshly precipitated binoxide of manganese (Weldon mud), and
sulphuric acid, in the presence of a large excess of the said hydrocarbons or
derivatives and separating from the unaltered material the aldehyde produced,
substantially as described.
2. The process of aldehydation of the methyl group in aromatic hydrocarbons,
as for example toluene or xylene, or their substitution derivatives, (as for example
chloro- or nitro-toluene), which process consists in the treatment of the said
hydrocarbons or derivatives with an oxidizing agent in such a proportion that
the oxidizing agent is insufficient for the oxidation of the total methyl to alde-
hyde and subsequently in separating from the unaltered material the aldehyde
produced.
J. C. MEWBURN & ELLIS.
55 and 56, Chancery Lane, London, Chartered Patent Agents.