Cbemistry. ~ On the ox idation of organic iodine compounds by means
of organic per~a cids. By J. BÖESEKEN and G. C. C. C. SCHNEIDER.
(Communicated at the meeting of October 25. 1930).
One of us (B.) with a number of collaborators I) has shown that in
many cases oxidation with per~acetic acid presented another image than
with per~benzoic acid.
Where the latter of ten give rise to the formation of oxides (I). oxida~
tion with per~acetic acid appeared to result in an addition of this acid
to the double bond with formation of glycol~mono~acetate (II).
That we have not to do here exclusively with an accidental difference
caused by another solvent. as the Russian investigators ARBUSOW and
MICHAILOW 2) suppose. who take in both cases the oxide as primary
product. which th en passes into a glycol~acetate (lIl a and b) on oxidati on in acetic acid solution.
1. C 6H sCOOOH
11. CH 3 COOOH
m".
oxide
+ unsaturate bond - C 6H sCOOH + oxide.
+
-- glycol monoacetate.
-- acetic acid + oxide.
+
+ acetic acid -- glycol acetate.
appears from the oxidation of stilbene. which with per~benzoic acid
passes into the oxide. which is not attacked by ace tic acid. while jt
forms hydro benzoine acetate with per~acetic acid.
In the oxidation of aromatic iodine compounds we have also found
a distinctly different behaviour of the two organic per~acids .
The aromatic iodoso~ and iodo~compounds have been discovered by
WILLGEROTH 3). who obtained the former by the decomposition of iodide~
chlorides with water. or preferably with caustic alkalies. Afterwards these
and the iodo~compounds have also been obtained by direct oxidation of
iodine compounds with nitric acids and other oxidizers. like NaOBr etc.
BAMBERGER and HILL have used CARO's acid. i.e. per~sulphuric acid.
for this purpose ; hen ce it was to be expected th at the organic per~acids
would appear to be efficient oxidizers.
We treated a number of compounds from different classes: C 6H sI.
0~C6H4I2' the iodine toluenes. the iodine benzoic acids. the iodine
sulphonic acids. iodine nitro~benzenes. and di~iodine ethyl ene. resp.
I) Recueil d. Trav. chim. d . Pays-Bas "7. 683. 69 ... 839 (1928) .•8 363 (1929).
2) Journ. f. pr . Ch . (2) 127. 92 .
3) B. 25. 3494 (1892).
828
with per~acetic acid and per~benzoic acid. and with a single exception
we could always obtain the iodoso~ and iodo~compounds.
In connection with what was said in the introduction. these two oxi~
dizers appeared to behave differently: with per~acetic acid always the
iodoso compound was obtained. and mostly in the form of its acetate.
hence an addition of the per~acetic acid; with per~benzoic acid the
iodo compound was always directly obtained with the ordinary iodides.
With ortho iodine~benzoic acid and paraiodine~sulphonic acid the
oxidation (also in case of after~treatment with per~benzoic acid) appeared
to stop with the iodoso compound; probably this is in connection with
the dipole character of these compounds. If the ordinary iodoso acetates.
which had been obtained with per~acetic acid. were subjected to an
after~treatment with per~benzoic acid. also these passed into the iodo
compounds. I)
The structure of orthoiodoso benzoic acid is of ten supposed to be
ring~shaped. because it crystallizes weil in contrast with the other iodoso
compounds. In view of the analogous properties of para-iodoso sulphonic
acid this structure seems improbable to me. and they are to be consi~
dered as internal salts without ring structure.
IOH+
• hence to be put on a line with the different diazonium~
C 6H 1
S03-
sul ph on ic acids and carbonic acids. which are also better formulated as
dipoles than as ring~shaped compounds.
It further appeared possible in a few cases to prepare iodoso~ or iodo~
compounds which so far had not been obtained in any other way. e.g.
ortho~di~iodo~benzene. the before~mentioned para~iodoso~sulphonic acid.
and di~iodo~ethylene. The oxidations take place at the temperature of
about 20°
and are mostly completed after 24 hours; the reaction
produets : iodoso acetates. resp. iodoso acid. and iodo~compounds are
obtained mostly in pure state. and in a very good yield.
1st Example :
10 gr. C6H5I dissolved in 40 cc. 9.5 Ofo per~acetic acid. after 24 hours.
gave an abundant crystallisation of iodoso~benzene~diacetate. Melt. p=156°.
active oxygene = 4.85 % calculated 4.97 Cfo.
Total yield 15 gr.
c..
I) It appeared. however. that in a single case a continued shaklng with per-acetic acid
caused the oxidation to result in the iodo compound. so that the difference in behaviour
of the two oxidizers must be found in the dipole character of the iodoso compound.
829
2.5 gr. C6H5I dissolved in 80 gr. 4 % chloroformic solution of per~
benzoic acid. After 18 hours a substance crystallizing in white leaflets.
has been formed.
Active oxygene 13.45 %. calculated 13.6 Ofo.
3 gr. iodosobenzene acetate dissolved in 40 gr. 5.6 % chloroformic
solution of perbenzoic acid; after some time 1.8 gr. of iodobenzene
(calculated 2.2 gr.) was deposited.
2 nd Example. Para iodoso sulphonic acid.
5 gr. p~1 C 6H 4S0 3 H were treated with 10 cc. 13 Ofo per~acetic acid.
Within a few minutes a white precipitate beg ins to form; after a few
hours af ter sucking off. the substance was washed with anhydrous acetic
acid and dried.
This substance could be recrystallized from boiling water.
Active oxygen. Found 5.2 0'0' calc. 5.3 0 / 0 , In dry condition the point
of decomposition is sharp at 156°.4 (weak detonation).
5 gr. iodine benzene sul ph on ic acid dissolved in 90 gr. chloroformic
solution containing 6.7 % per~benzoic acid gave. af ter some minutes.
a feebly yellow precipitate. which was sucked off. washed. and dried in
vacuo; after 3 hours' drying this had 3.6 Ofo active oxygen. af ter 18 hours
only 3.9 0 / 0 , At first it was supposed to contain benzoic acid. no trace
was found by steam~distillation.
After recrystallisation from H 20 the substance becomes colourIess.
and the content of active oxygen was 5.2. the point of explosion 156.6.
This once recrystallized product did not absorb any chloroform; it is.
therefore. probable that the pale~yellow amorphous oxidation product
formed at first. has absorbed some chloroform (resp. a little iodine
benzene sulphonic acid). in consequence of which the active oxygen was
found too low.
The complete investigation will be published elsewhere.
Laboratory of Organic Chemistry of the
Technical University .
Delft. October 1930.