Manufacture of Acetyl-compounds of Substitution Derivatives of Aromatic Amines.
Year: 1898

page_text: Date of Application, 11th Aug., 1898
Complete Specification Left, 28th Apr., 1899-Accepted, 15th July, 1899
PROVISIONAL SPECIFICATION.
Manufacture of Acetyl-compounds of Substitution Derivatives
of Aromatic Amines.
I, OLIVER IMRAY, of Birkbeck Bank Chambers, Southampton Buildings, Chancery
Lane, in the County of London, Chartered Patent Agent, do hereby declare the nature
of this invention (as communicated to me from abroad by The Farbwerke vormals:
Meister Lucius and Brüning, of Hoechst a/Main, in the Empire of Germany, Chemical
Manufacturers) to be as follows:-
The acetylisation of amido-compounds has been carried out hitherto by boiling them
for a considerable time in an excess of glacial acetic acid in a vessel provided with an
inverted condenser, or, if amido-sulphonic acids were concerned, by heating the dried
alkali salts of the latter for some time with an excess of glacial acetic acid or
acetic anhydride.
These methods do not produce good results with all compounds. Some bodies do not
react at all or only very slowly with the acid in glacial acetic acid on account of their
slight degree of solubility, as for instance, many amidosulphonic acids, or they become
resinous and decompose by a prolonged heating at a high temperature. This is the
case with di- and triamido-derivatives and with triphenylmethane compounds.
My correspondents have found, that primary as well as secondary amido-compounds
and their substitution products may be acetylised in an easy and simple manner by
heating their aqueous solutions with the calculated quantity of acetic anhydride at a
moderate temperature. It was not to be foreseen that an acetylisation with acetic
anhydride in an aqueous solution would be possible, on the contrary, it was to be
expected that the anhydride would at once combine with the water and the dilute
acetic acid thus resulting would not effect acetylisation at all or only at a very high
temperature.
Experiments have shewn, however, that acetic anhydride reacts much more quickly
with an existing amido-group than it is decomposed by water.
The acetylisation of amido-compounds in an aqueous solution with acetic anhydride
offers particular technical advantages. Closed vessels with inverted condensers are not
needed, as the reaction succeeds in any open vessel or wooden vat provided with an
agitator. Neither is there required a high temperature and continued heating, so
that the frequent appearance of products of decomposition is avoided and the acetyl-
compounds thus obtained are characterised by their superior purity.
It is also not necessary according to this method to separate in a dry state the
amido-compounds to be acetylised. Thus, for instance, the aqueous solution of the
reduction product obtained by reducing meta-dinitrobenzene may be acetylised
directly by adding acetic anhydride and then isolating by filtration the crystalline
diacetyl-m-phenylenediamine which separates.
• A special advantage of this method consists also in the possible acetylisation of one
or more amido-groups by adding the calculated molecular quantity of anhydride to
the aqueous solution of poly-amido-derivatives.
The acetylisation of the bases succeeds best by dissolving them in water or by

page_text: suspending them in a finely divided state if insoluble or soluble with difficulty, and
then running in, while stirring, the calculated quantity of acetic anhydride at
about 50°-90° C.
The amido-derivatives of the triphenylmethane series may also be dissolved, for
instance in slightly dilute hydrochloric or acetic acid and then acetylised with
anhydride. The amido-acids are best transformed into the normal alkali salts
and employed in concentrated aqueous solutions. The acetyl compounds, for the
most part very easily soluble, are then salted out from the concentrated solutions or
the solutions are evaporated to dryness.
I will illustrate the above described method by the following examples :-
:-

page_text: Manufacture of Acetyl-compounds of Substitution Derivatives
of Aromatic Amines.
I, OLIVER IMRAY, of Birkbeck Bank Chambers, Southampton Buildings,
in the County of London, Chartered Patent Agent, do hereby declare the
nature of this invention (as communicated to me from abroad by The Farbwerke
vormals: Meister Lucius & Brüning, of Hoechst a/Main, in the Empire of Germany,
Chemical Manufacturers) and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement:-
:-
Acetic anhydride reacts in presence of water in the cold upon aromatic amines
effecting formation of acetyl-compounds as shewn by Hinsberg (Ber. XXIII 2962).
Considering the great capability of reaction of aromatic amines with acetic
anhydride, which is such that when mixed in an anhydrous state in the cold the
anhydride and amine react violently upon each other with evolution of heat, this
reaction is not very surprising.
The sulphonic and carboxylic acids of aromatic amines do not possess such
capability of reaction with acetic anhydride, which does not react upon these acids
when mixed with them in the cold. To obtain their acetyl-compounds boiling for a
considerable time with acetylising agents has hitherto been necessary.
My foreign correspondents have found, that these acids may also be transformed in
the cold, that is to say, without boiling, into their acetyl-compounds, if they are
mixed in an aqueous solution, or suspended in water, with acetic anhydride.
It is remarkable, that in this respect the acids show the same behaviour as the
amines, notwithstanding their inferior capability of reaction with the anhydride.
The reaction takes place quickly and satisfactorily and is generally completed within
a few minutes thus affording simple means for the manufacture of all those acetyl-
compounds which could hitherto be obtained only in a comparatively complicated
manner.
For the practical application of this method the normal salts of the acids are best
employed, but the free acids also react in the stated manner in presence of sodium
acetate or of organic bases, such as quinoline and dimethylaniline.
It is neither necessary nor advantageous to cool with ice while the reaction is
proceeding as stated in Ber. XXIII.
Ordinary temperature or average temperature of 50°-60° C. is the most
favourable.
The method, apart from its simplicity, has this advantage that, for instance,
diaminesulphonic or carboxylic acids may be acetylised once or twice, accordingly as one
or two molecules of acetic anhydride are employed, and further, that amidophenol-
sulphonic acids may be acetylised only in the NH₂ group or in the NH, and OH
groups, accordingly as the sulphonic or the OH group is saturated with alkali a result
which hitherto could never be completely attained by the old process.
EXAMPLE.
1. 23-3 kilos. of calcium metanilate of 82.8 per cent. strength are dissolved with
aid of heat in about 100 litres of water, then allowed to cool to ordinary temperature,
whereupon there are added, while well stirring, 12 kilos. of acetic anhydride. As
soon as the anhydride has disappeared the whole is evaporated to dryness.

page_text: 3. 153 kilos. of para-amidosalicylic acid are dissolved with 7 kilos. of sodium
carbonate in 100 litres of hot water and acetylised on cooling by stirring in 12 kilos.
of acetic anhydride. The acetylised acid may be isolated by precipitation with
hydrochloric acid.
4
4. 30 kilos. of 2:8:6-amidonaphtholsulphonic acid of 75 per cent. strength are
dissolved in 7 kilos, of sodium carbonate and 100 litres of water, whereupon there
are added at ordinary temperature and while stirring 12 kilos. of acetic anhydride.
The solution of the acetylamidonaphtholsulphonic acid, thus obtained, may be
directly used or the acid may be isolated in a dry state by evaporation of the
solution..
5. 23-8 kilos. of 1: 4-naphthylenediaminesulphonic acid are dissolved in 7 kilos.
of sodium carbonate and 100 litres of water and then transformed into the mono-
acetyl-compound by adding 11 kilos. of acetic anhydride. The solution may be
directly employed or the acid may be precipitated from its concentrated cold aqueous
solution by the addition of hydrochloric acid.
6. 80 kilos. of the acid sodium salt of a-1: 3: 6-naphthylaminedisulphonic acid
of 83-8 per cent. strength are dissolved with aid of heat together with 14 kilos. of
sodium carbonate in about 150 litres of water, whereupon there are added while
cooling 25 kilos. of acetic anhydride, the whole being evaporated to dryness. By
this process may be manufactured the acetyl-compounds of sulphanilic acid, ortho-
toluidinesulphonic acid, paratoluidinesulphonic acid, meta- and para-amidobenzoic
acids, ortho- and para-amidophenolsulphonic acids, ortho- and para-amidophenolether-
sulphonic acids, a-1 : 3-, 1 : 5-, 1: 6-, 1: 7- and 1: 8-naphthylaminesulphonic acids,
a-14: 6- and 1:4: 7-naphthylaminesulphonic acids, 8-2: 5-, 2: 6-, and 2:8-
naphthylaminesulphonic acids, B-2: 6: 8-naphthylaminedisulphonic acid, 1:8:4-
amidonaphtholsulphonic acid, 1:8:3:6, 1:8:4:6- and 1:5:3: 7-amidonaph-
tholdisulphonic acids, 1:4: 7-, (1:4: 6)- naphthylenediaminesulphonic acid, para-
and meta-phenylenediaminesulphonic acids and meta-toluylenediaminesulphonic acid.
Having now particularly described and ascertained the nature of this inven-
fion and in what manner the same is to be performed, I declare that what I
claim is
}
1. The herein described manufacture of acetyl- compounds of amidosulphonic and
amidocarboxylic acids and their derivatives, by treating the normal salts of these
acids in an aqueous solution or suspended in water at ordinary or average temperature
(about 50° C.) with acetic anhydride.
2. The manufacture of acetyl-compounds of sulphanilic, metanilic, ortho-toluidine-
sulphonic, para-toluidinesulphonic, ortho-, meta- and para-amidobenzoic, para-amido.
salicylic, ortho- and para-amidophenolsulphonic, ortho- and para-amidophenolether-
sulphonic, a-1 3-, 1 : 4-, 1: 5-, 1 : 6-, 1 : 7-, 1 : 8-naphthylaminesulphonic, a-1: 3: 6-,
1:46, 14: 7-naphthylaminedisulphonic, B-2: 5-, 2:6, 2:8-naphthylamine-
sulphonic, 8-26 8-naphthylaminedisulphonic, 28: 6-, 1 8 4-amido-
naphtholsulphonic, 18: 3: 6-, 18:4: 6-, 1:5:3:7- amidonaphtholdisul-
phonic, 147-, (14 6)-naphthylenediaminesulphonic acid, para-phenylene-
diaminesulphonic, meta-phenylenediaminesulphonic, meta-toluylenediaminesulphonic
acids, by treating their normal salts in an aqueous solution or suspended in
water at ordinary or average temperature (about 50° C.) with acetic anhydride
substantially as set forth.