Process for the Preparation of Iodo Compounds of the Phenol Series of the Aromatic Oxy-carbon Acids and Pyrrol.
Year: 1893

page_text: Date of Application, 4th Aug., 1893-Accepted, 21st Oct., 1893
COMPLETE SPECIFICATION.
Process for the Preparation of Iodo Compounds of the Phenol Series
of the Aromatic Oxy-carbon Acids and Pyrrol.
A communication from Dr. EMANUEL FRÖHLICH, of Charlottenburg, in the
Empire of Germany.
I. ALFRED JULIUS BOULT of 323 High Holborn in the County of Middlesex,
Chartered Patent Agent, 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 :-
Schutzenberger and Seugenwald (J. 1862, 413) obtained di- and tri- iodophenol
by the action of iodine chloride on phenol and paraiodophenol respectively
(J. 1865, 524). I have discovered that by appropriate changes in the conditions
of experiment, the body di-iodo-phenol-iodide which was first prepared by
Messinger & Vortmann, (transactions of the German Chemical Society 22, 2313)
is obtained instead of the first-named products; and I have afterwards further
found that my method is adapted not only to the preparation of all possible iodo
substitutes of phenol and iodo substitutes of the aromatic carboxy acids, (replaced
either in their nuclei (original group) as well as the hydroxyl group) but also to
the conversion of pyrrol and alkylpyrrol into respectively tetraiodo-pyrrol and
tetraiodo-alkylpyrrol.
A great technical advantage which my method possesses over the processes of
iodization hitherto employed lies in the fact that by its application the expensive
iodine can be replaced to half its extent, by the cheaper chlorine.
Thus, whereas according to the DRP 35120 4 molecules of iodine are required
for the conversion of 1 molecule of pyrrol into 1 molecule of tetraiodo of pyrrol
according to the equation
C¸H¸OH + 3 ICI = CH¸I¸O1 + 3 HCI.
In place of free iodic chloride we may for practical purposes employ the equally
accessible chlor-iodo-hydrochloric acid (ICI, HCI).
lodic bromide or brom-iodo-hydrobromic acid (IBrHBr) respectively act in a
similar manner to iodic chloride or chlor-iodo-hydrochloric acid.
As a characteristic feature of my method, I would further remark that all the
reactions between iodic chloride or chlor-iodo-hydrochloric acid with the phenols etc.
take place at normal temperature.
Thus chlor-iodo-hydrochloric acid acts in many cases e.g. towards carbolic acid,
more energetically than free iodine, which yields di-iodo-phenol-iodide only when
warmed (reports of German Chemical Society 22, 2313 and D R P No. 55328)—
in other cases again as e.g. towards the different alkali-phenols it acts more gently

page_text: dissolved in alcohol with addition of animal charcoal and the filtered alcoholic
solution precipitated with water. Yellowish white tetraiodo-pyrrol with its
characteristic properties is obtained.
EXAMPLE VII.
0.8 kg. of methyl pyrrol are suspended in a solution of 3.2 kg. of sodic hydrate
in 300 litres of water and into the mixture 6.5 kg. of iodic chloride or 8 kg. of
chlor-iodo-hydrochloric acid are allowed to flow gradually. The precipitate which
separates out is filtered off and dissolved in alcohol with addition of animal
charcoal and again precipitated from this solution by means of water.
tetraiodo-methyl-pyrrol is dried at a low temperature and forms a brown yellow
powder which in its properties, insolubility in alkalies included, is very similar to
tetraiodopyrrol.
The
Having now particularly described and ascertained the nature of the said inven-
tion, as communicated to be by my foreign correspondent, and in what manner
the same is to be performed, I declare that what I claim is :-
I. The process for the preparation of di-iodo-phenol-iodide, iodo cresol iodide
(o-, m-, p- compounds) diiodoresorcinic iodide, thymoliodide, dithymoliodide,
carvacroliodide, naphtholiodide, consisting in allowing indic chloride or chlor-iodo-
hydrochloric acid in substance or in aqueous, alcoholic or sodic chloride or neutral
solution to act upon alkaline solution of the following phenols: phenol cresol,
o-, m-, p compounds, resorcin, thymol, carvacrol, naphthol.
II. The process for the preparation of isobutyl phenol iodide methyl-, ethyl-,
n-propyl-isobutyl-isoamyl-o-cresoliodide n-propyl-, isobutyl-, isoamyl-, m-cresoliodide
consisting in the employment in process I above, in place of the phenols there
enumerated of the following:-Isobutylphenol, methyl-, ethyl-, n-propyl-, isobutyl-,
isoamyl-o-cresol, n-propyl-, isobutyl-, isoamyl-m-cresol.
III. The process for the preparation of iodo guiacol iodide and of eugenol-iodide
consisting in employment in process I in place of the phenols there named of
guiacol and eugenol.
IV. The process for the preparation of tetr-iodo-oxy-sulphide of benzol consisting
in the employment in process I, in place of the phenols there named, of di benzyl
sulphoxide.
V. The process for the preparation of iodo salicylic acid iodide and iodo-oxy-
toluylic acid iodide consisting in the employment in process I of salicylic acid, or,
oxy o- m- p- toluylic acid in place of the phenols there named.
VI. The process for the preparation of tetr-iodopyrrol consisting in allowing
iodic chloride or chlor iodo hydrochloric acid in substance or in aqueous, alcoholic,
sodic chloride, acid or neutral solution to act upon an aqueous solution of pyrrol
in presence of a base or of a basic salt.
VII. The process for the preparation of tetraiodo-, methyl-, ethyl-, propyl-,
isobutyl-, pyrrol consisting in employment in process VI instead of the there
named pyrrols, of methyl-, ethyl-, propyl-, or isobutyl pyrrol.
VIII. The preparation of the iodo compounds enumerated in I-VI by employ-
ment in place of the there named iodic cloride or chlor iodo hydrochloric acid, of
bromic iodide or brom-iodo-hydrobromic acid obtained from iodic bronide and
hydrobromic acid.
Dated this 4th day of August 1893.
W. P. THOMPSON & BOULT,
Of London, Nottingham, Liverpool, and Manchester,
Agents for the Applicant.