Laboratory Methods of Organic Chemistry - Sciencemadness Dot Org

IODOXYBBNZBNB 285
into a test tube, gives a copious deposit of crystals. After the
concentrated solution has cooled the crystalline material is collected
at the pump, etc.
In general the iodonium bases are formed from iodoso- and iodoxycompounds
in the presence of alkali, preferably silver oxide; the two
organic iodine compounds combine with elimination of iodate.
0. wmT C6H6.I.C6HS
C6H6.IO+ ^>I-C6H5 ^25. 5H +NaI03.
Iodoxybenzene is formed, together with iodobenzene, from iodosobenzene
by intermolecular dismutation :
C6H6.IO + OI.C6H5 —• C6H5.l/ +C6H5I,
just as nitrous acid undergoes dismutation to nitric acid and nitric oxide.
This reaction takes place to a slight extent even in the cold ; hence the
appearance of the iodonium base as a by-product in the preparation of
iodosobenzene.
The iodoso- and, in particular, the iodoxy-compounds decompose
with a pufE when heated, since the oxygen which they contain is present
in a state of tension. They liberate an equivalent amount of iodine
from acidified potassium iodide solution and are thereby reconverted
into iodobenzene.
The basic function of the iodine in the iodonium bases, which
correspond exactly to the ammonium, sulphonium, and oxonium bases,
is most interesting. A molecule of diphenyliodonium iodide has the
same atoms as two molecules of iodobenzene and decomposes on heating
with liberation of heat (contrast other dissociations such as those of
N2O4, NH4C1, PC15) into two moles of C6H5I. Test with a small sample
in a tube.
As is still the case to-day with the diazonium compounds, so it was
for long thought that the aromatic compounds containing multivalent
iodine, which were simultaneously and independently discovered by
V. Meyer and by C. Willgerodt, formed a class of substances peculiar to
the aromatic series. But in 1909 Thiele found analogues to all these
compounds amongst the defines, with chloroiodoethylene CHC1=CHI as
their simplest parent substance. Even methyl iodide, at low temperatures,
can combine with chlorine, but the product decomposes again
readily, yielding methyl chloride and iodine chloride (replacement of
iodine by chlorine). The derivatives of multivalent iodine are not
stable, unless the iodine is attached to a doubly bound carbon atom.
(d) Benzene from Aniline.-—An alkali stannite solution is prepared
by mixing a solution of 50 g. of sodium hydroxide in 60 c.c.
of water with the turbid solution of 40 g. of stannous chloride in