Chlorine (III) oxide properties, structure, uses

The chlorine (III) oxide is an inorganic compound whose chemical formula is Cl_twoOR₃. Corresponds to chlorous acid anhydride, HClO_two. It is a dark brown solid, highly explosive even at temperatures below 0ºC, and poorly characterized. That is why it is an object of interest for computational studies..

Chemically it is a covalent oxide, so there are Cl-O bonds and a discrete molecule of Cl_twoOR₃ (lower image). Such a molecule can well be formed by dehydrating HClO_two, or subjecting it to photolysis at low temperatures. The detail is that it decomposes producing Cl_two, OR_two, or other thermodynamically stable chlorine oxides.

Since Cl-O bonds are poorly polar, the Cl molecule_twoOR₃ has a small dipole moment; therefore, it does not dissolve well in water or interact with other polar solvents. Its instability is such that it is not known for commercial or potential uses (nor would its applicability be viable as an explosive).

The main reason for its instability may be due to the electronic characteristics of the supposed Cl³⁺ (assuming a purely ionic character). In fact, its oxidation states +1 and +5 are the most stable when chlorine forms compounds with oxygen..

Article index

• 1 Properties
• 2 Structure of chlorine (III) oxide
  • 2.1 Isomers
• 3 Nomenclature
• 4 Uses
• 5 References 

Properties

Because its characterization is poor and poorly documented, there is not much to say about its properties except the following points:

-It has a molecular mass of 118.903.

-It is a solid dark brown; although it can sublimate gaseous chlorine, giving off yellowish green vapors.

-It lacks both a boiling point and a melting point, since at 0ºC it explodes (and at colder temperatures too).

-Its solubility in water is estimated to be around 3.42 g / 100 mL, which proves that it is a covalent molecule of low polarity..

-Reacts with water (the little that dissolves) to become HClO_two:

Cl_twoOR₃ + H_twoOR <=> 2HClO_two

Structure of chlorine (III) oxide

The image showed the molecular structure of Cl_twoOR₃ with a model of spheres and bars. Although it may not seem so at first glance, the unspoken implications of its links and spatial arrangements are more complicated than they appear. This structure corresponds to one of the many possible isomers for this compound..

The red spheres correspond to oxygen atoms, and the green spheres to chlorine atoms. The chlorine on the left has a trigonal pyramid geometry, with a pair of free electrons; so it can be assumed that their hybridization must be sp³. An oxygen atom acts as a bridge between the two chlorines, Cl-O-Cl.

Isomers

What are the other isomers? In theory, nine are calculated, of which four are the most stable (including the one in the image). The other three would have structures such as:

-ClClO₃. Very similar to the one explained, but with a Cl-Cl bond.

-ClOOOCl (1). In this isomer there is a bridge of three oxygens that separate the two chlorine atoms (remember the angular geometry of H_twoOr to visualize it).

-ClOOOCl (2). The same oxygenated bridge is also present in this isomer, except that the two chlorine atoms are eclipsed in space; one opposite the other, while in the above isomer they are distant.

Nomenclature

Its name, chlorine oxide (III), corresponds to the one assigned according to the stock nomenclature. Here it is assumed that chlorine has an oxidation state of +3; but it does not mean that the Cl cation³⁺ may be present. It is a molecule, not a network of ions.

Another name by which Cl is also known_twoOR₃ is dichloro trioxide, according to the systematic nomenclature.

And finally, not so common (despite being governed by the traditional nomenclature), there is the name chlorous anhydride to refer to this compound. This name is due to the fact that, as already explained, the Cl_twoOR₃ occurs when HClO_two condenses releasing water.

Applications

As it is a chlorine oxide, the most immediate use that could be thought of for Cl_twoOR₃ It is like an oxidizing agent, capable of neutralizing organic impurities and microbes. However, it is very unstable, as well as explosive, so it is not even considered useful for this purpose..

For sure there is no information on how the Cl would behave._twoOR₃ under enormous pressure (if it doesn't explode in the process). Under normal conditions, it appears to be nothing more than a relatively stable and differentiable intermediate between other more stable chlorine oxides..

Computationally, however, it has been the object of study to determine free radical mechanisms that involve various species of chlorine and oxygen..

References

1. Shiver & Atkins. (2008). Inorganic chemistry. (Fourth edition). Mc Graw Hill.
2. Wikipedia. (2019). Dichlorine trioxide. Recovered from: en.wikipedia.org
3. Dale L. Perry. (2011). Handbook of inorganic compounds. (second edition). CRC Press Taylor & Francis Group.
4. Richard C. Ropp. (2013). Encyclopedia of the Alkaline Earth Compounds. Elsevier.
5. Kim K. H., Han Y.K., and Lee Y. S. (1999). Basis set effects on the stability of the Cl2O3 isomers using B3P86 and B3LYP methods of density functional theory. Journal of Molecular Structure THEOCHEM 460 (1-3): 19-25.