Improvements in the Manufacture of Vanillin.
Year: 1893

page_text: Date of Application, 15th Dec., 1893
Complete Specification Left, 17th Sept., 1894-Accepted, 20th Oct.. 1894
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Vanillin.
I, SYDNEY PITT, of Sutton, in the County of Surrey, Gentleman, (a communi-
cation to me from abroad by The Chemische Fabrik auf Actien vorm. E. Schering,
of 170 Müllerstrasse, Berlin,) do hereby declare the nature of this invention to be
as follows:-
The invention consists in the preparation of vanillin from protocatechuic
aldehyde by
(a) Converting the mono-metallic salts of protocatechuic aldehyde into aromatic
ethers of the type of benzyl-phenyl ether (for instance into the monobenzyl ether
or trinitrophenyl ether of protocatechuic aldehyde).
(b) Subsequently methylating a metallic salt of this aromatic protocatechuic
aldehyde ether, and
(c) Eventually splitting off the vanillin from the aromatic vanillin ether so
formed.
The formation of vanillin may be expressed by the following equations :

page_text: CHO
CHO
In the first operation, the conversion into the above mentioned aromatic mono-
ethers of protocatechuic aldehyde is best effected in the following manner. One
molecular proportion of alkaline hydroxide is added to the alcoholic solution of
protocatechuic aldehyde, then one molecular proportion of benzyl chloride, or one
molecular proportion of chlordinitrobenzene (m.p. 50° C.), or one molecular pro-
portion of chlortrinitrobenzene (m.p. 83° C.), and the whole warmed several hours
on the water-bath. The ether is isolated in the usual way, separated from any
di-ether that is formed at the same time by dissolving in alkali liquor, and then
purified either by crystallisation or preferably by conversion into the sodium or
potassium salt, which are not very soluble in aqueous alkali solutions.
¸ОCH CH (1)
For example; monobenzyl ether C,H-OH
(2). 1.38 kilos. proto-
CHO
(4)
catechuic aldehyde are dissolved in about 3 kilos. spirit, alcoholic potassium
hydroxide solution containing 0.56 kilos. potassium hydroxide and 1.27 kilos.
benzyl chloride are then added to the solution and the mixture warmed on the
CHO
(4)
catechuic aldehyde are dissolved in about 3 kilos. spirit, alcoholic potassium
hydroxide solution containing 0.56 kilos. potassium hydroxide and 1.27 kilos.
benzyl chloride are then added to the solution and the mixture warmed on the

page_text: water bath for several hours. The residue obtained after evaporation of the aiconor
is taken up with ether and the ethereal solution extracted with dilute caustic soda
solution. The alkaline extract can then be either supersaturated with caustic soda
solution, which precipitates the comparatively insoluble sodium salt, or it is more
advantageous to first acidify, dissolve the separated cake in spirit and add just
sufficient caustic soda solution to precipitate the sodium salt of protocatechuic
aldehyde monobenzyl ether. The free protocatechuic aldehyde monobenzyl ether
crystallises out of alcohol in compact leaves and melts at 122° C.
The corresponding mono-ethers with chlorodinitrobenzene (m.p. 50° C.) and with
chlorotrinitrobenzene (m.p. 83° C.) are obtained in the same way.
In the second operation, the methylation can best be effected in the following
The alkali salts of the mono-ethers are treated in solution in methyl
In place of the methyl halide a salt of methyl-
alcohol with methyl iodide.
sulphuric acid can also be employed in aqueous solution.
with the benzyl protocatechuic aldehyde sodium salt protocatechuic
alcohol with methyl iodide.
in place of
sulphuric acid can also be employed in aqueous solution.
Starting with the henzyl protocatechuic aldehyde sodium salt protocatechuic
OCH, CH (1)
aldehyde benzylmethyl ether CH-OCH,
(2) is thus obtained, which is
CHO
(4)
5
identical with the benzylvanillin prepared by oxidation of benzylisocugenol.
For example: 2.28 kilos. benzylprotocatechuic aldehyde and 1.5 kilos. methyl
iodide dissolved in 10 kilos. methyl alcohol, are warmed for some hours on the
water-bath with a solution of 0.56 kilos. potassium hydroxide in methyl alcohol.
The benzylmethyl ether formed is isolated in the ordinary way.
.It is obvious that the methylation can also be effected directly after the benzyl-
ation, without separating the benzyl ether of protocatechuic aldehyde, by simply
adding a further molecular proportion of alkali and a molecular proportion of
methyl iodide to the solution after benzylation has been effected; but it
advisable.
not
In the third operation the aromatic ethers so obtained are saponified in a well
known way.
For example: Analogous to the decomposition of phenylbenzyl ether (Beilstein's
Lehrbuch der Organ. Chem., vol. II., p. 663) 1 kilo. benzylvanillin is heated on a
Both bodies are
water bath with concentrated hydrochloric acid and frequently stirred. Decom-
position into benzyl chloride and vanillin is thus effected.
separated by known methods. The decomposition is also effected slowly even at
ordinary temperatures.
Vanillin can also be split off from the dinitro- and trinitro-phenyl vanillin ethers
obtained in the manner previously described, for instance, by heating with caustic
soda solution.
Dmber 1893.
Y DITT
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Vanillin.
I, SYDNEY PITT, of Sutton, in the County of Surrey, Gentleman, (a com-
munication to me from abroad by The Chemische Fabrik auf Actien vorm.
E. Schering, of 170 Müllerstrasse, Berlin,) 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 :-
.
This invention, like that to which my Patent No. 24177 relates, is based on the

page_text: substitution, in protocatechuic aldehyde, for the hydrogen of the hydroxyl group
occupying the para position in relation to the COH group, of a group which easily
may be removed again; in this case the benzyl group, that is to say, compounds of
the type of p-benzyl-protocatechuic aldehyde are first obtained; these are sub-
sequently methylated and submitted to a splitting operation.
The method consists in the combination of the following three processes:
(a) Converting the mono-metallic salts of protocatechuic aldehyde into aromatic
ethers of the type of p-benzyl-protocatechuic aldehyde.
(b) Subsequently methylating a metallic salt of this aromatic protocatechuic
aldehyde ether and
(c) Splitting off the vanillin from the aromatic vanillin ether so formed.
The formation of vanillin may be expressed by the following equations :
CHO
сно
In the first operation, the conversion into the above mentioned aromatic mono-
ethers of protocatechuic aldehyde is best effected in the following manner.
One 2
molecular proportion of alkaline hydroxide or it may be alkaline earth hydroxide
or an alkali or alkaline earth salt of carbonic or phosphoric acid is added to the
alcoholic or watery solution of protocatechuic aldehyde, then one molecular
proportion of a compound of the type benzyl chloride and the whole warmed
several hours on the water-bath. The ether is isolated in the usual way; separated 2
from any di-ether that is formed at the same time by dissolving in alkali liquor,
and then purified either by crystallisation or preferably by conversion into the
sodium or potassium salt, which are not very soluble in aqueous alkali solutions.
OCH, CH. (1)
For example; monobenzyl ether C.H.-OH
(2) 1.38 kilos. proto-
Спо
catechuic aldehyde are dissolved in about 3 kilos. spirit, alcoholic potassium 30
hydroxide solution containing 0.56 kilos. potassium hydroxide and 1.27 kilos. benzyl
chloride are then added to the solution and the mixture warmed on the water bath
for several hours. The residue obtained after evaporation of the alcohol is taken

page_text: up with ether and the ethereal solution extracted with dilute caustic soda solution.
The alkaline extract can then be either supersaturated with caustic soda solution,
which precipitates the comparatively insoluble sodium salt, or it is more advan-
tageous to first acidify, dissolve the separated cake in spirit and add just sufficient
caustic soda solution to precipitate the sodium salt of protocatechuic aldehyde
monobenzyl ether. The free protocatechuic aldehyde monobenzyl ether crystallises
out of alcohol in compact leaves and melts at 122° C.
The isomeric m-benzyl-ether that is formed at the same time melts at 113-114° C.
and forms an easily soluble sodium salt remaining in the filtrate.
The production of p-benzyl-protocatechuic aldehyde may also advantageously be
carried out by dissolving the potassium salt of protocatechuic aldehyde in water
and boiling it with benzyl chloride at the return condenser.
In the second operation, the methylation can best be effected in the following
manner. The alkali salts of the mono-ethers are treated in alcoholic solution with
methyl iodide. In place of the methyl halide a salt of methyl-sulphuric acid can
also be employed.
Starting with the p-benzyl protocatechuic aldehyde sodium salt p-benzyl proto-
CHO
(4)
For example: 2.28 kilos. p-benzyl protocatechuic aldehyde and 1.5 kilos. methyl
iodide dissolved in 10 kilos. methyl alcohol, are warmed for some hours on the water-
bath with a solution of 0.56 kilos. potassium hydroxide in methyl alcohol. The
benzyl-methyl ether formed is isolated in the ordinary way.
In the third operation the aromatic ethers so obtained are saponified in a well
known way.
For example: Analogous to the decomposition of phenyl benzyl ether (Beilstein's
Lehrbuch der Organ. Chem., vol. II p. 663) 1 kilo. benzyl-vanillin is heated on a
water bath with concentrated hydrochloric acid and frequently stirred. Decom-
position into benzyl chloride and vanillin is thus effected. Both bodies are separated
by known methods.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
The manufacture of vanillin from protocatechuic aldehyde by transforming a
mono-metal salt of protocatechuic aldehyde into benzyl ether, methylating this
ether, and splitting off the vanillin from the ether so obtained.
Dated this 17th day of September 1894.
CARPMAEL & Co.,
Agents for the Applicant.