Iodine oxides are
chemical compounds
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
of
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...
and
iodine. Iodine has only two stable oxides which are isolatable in bulk, iodine tetroxide and
iodine pentoxide
Iodine pentoxide is the chemical compound with the formula I2O5. This iodine oxide is the anhydride of iodic acid, and the only stable oxide of iodine. It is produced by dehydrating iodic acid at 200 °C in a stream of dry air:
:2HIO3 → ...
, but a number of other oxides are formed in trace quantities or have been hypothesized to exist.
The chemistry of these compounds is complicated with only a few having been well characterized. Many have been detected in the atmosphere and are believed to be particularly important in the marine boundary layer.
Diiodine monoxide has largely been the subject of theoretical study, but there is some evidence that it may be prepared in a similar manner to
dichlorine monoxide
Dichlorine monoxide is an inorganic compound with the molecular formula Cl2O. It was first synthesised in 1834 by Antoine Jérôme Balard, who along with Gay-Lussac also determined its composition. In older literature it is often referred to as c ...
, via a reaction between
HgO and I
2. The compound appears to be highly unstable but can react with alkenes to give halogenated products.
Radical iodine oxide (IO), iodine dioxide (IO
2) and iodine tetroxide ((IO
2)
2) all possess significant and interconnected atmospheric chemistry. They are formed, in very small quantities, at the marine boundary layer by the
photooxidation of
diiodomethane
Diiodomethane or methylene iodide, commonly abbreviated "MI", is an organoiodine compound. Diiodomethane is a colorless liquid; however, it decomposes upon exposure to light liberating iodine, which colours samples brownish. It is slightly solub ...
, which is produced by macroalga such as
seaweed or through the oxidation of molecular iodine, produced by the reaction of gaseous ozone and iodide present at the seasurface. Despite the small quantities produced (typically below
ppt) they are thought to be powerful
ozone depletion agents.
Diiodine pentoxide (I
2O
5) is the
anhydride
An organic acid anhydride is an acid anhydride that is an organic compound. An acid anhydride is a compound that has two acyl groups bonded to the same oxygen atom. A common type of organic acid anhydride is a carboxylic anhydride, where the pa ...
of
iodic acid and the only stable anhydride of an iodine
oxoacid
An oxyacid, oxoacid, or ternary acid is an acid that contains oxygen. Specifically, it is a compound that contains hydrogen, oxygen, and at least one other element, with at least one hydrogen atom bonded to oxygen that can dissociate to produce ...
.
Tetraiodine nonoxide (I
4O
9) has been prepared by the gas-phase reaction of I
2 with O
3 but has not been extensively studied.
Iodate anions
Iodine oxides also form negatively charged
anions
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
, which (associated with complementary cations) are components of acids or salts. These include the
iodates and
periodate
Periodate is an anion composed of iodine and oxygen. It is one of a number of oxyanions of iodine and is the highest in the series, with iodine existing in oxidation state +7. Unlike other perhalogenates, such as perchlorate, it can exist in two ...
s.
Their
conjugate acids are:
The -1 oxidation state, hydrogen iodide, is not an oxide, but it is included in this table for completeness.
The periodates include two variants: metaperiodate and orthoperiodate .
See also
*
Oxygen fluoride
*
Chlorine oxide
Chlorine and oxygen can bond in many ways:
* chlorine monoxide, , chlorine (II) oxide
* chlorine peroxide, , dimer of chlorine (II) oxide
* chlorine dioxide, , chlorine (IV) oxide
* chloroperoxyl,
*chlorine trioxide, ClO3, chlorine (VI) oxide
* ...
*
Bromine oxide
References
{{Use dmy dates, date=March 2018
Oxides
Iodides
Iodine compounds