Oxides or oxides are compounds of various elements with oxygen. Almost all elements form such compounds. Chlorine, like other halogens, is characterized by a positive oxidation state in such compounds. All chlorine oxides are extremely unstable substances, which is typical for oxides of all halogens. Four substances are known whose molecules contain chlorine and oxygen.
- The gaseous compound from yellow to reddish in color with a characteristic odor (resembles the smell of Cl2 gas) is chlorine oxide (I). Chemical formula Cl2O. Melting point minus 116 ° C, boiling point plus 2 ° C. Under normal conditions, its density is 3.22 kg / m³.
- A yellow or yellow-orange gas with a characteristic odor is chlorine (IV) oxide. Chemical formula ClO2. Melting point minus 59 ° C, boiling point plus 11 ° C.
- Red-brown liquid - chlorine oxide (VI). Chemical formula Cl2O6. Melting point plus 3.5 ° C, boiling point plus 203 ° C.
- Colorless oily liquid - chlorine oxide (VII). Chemical formula Cl2O7. Melting point minus 91.5 ° C, boiling point plus 80 ° C.
Chlorine oxide with an oxidation state of +1 is the anhydride of weak monobasic hypochlorous acid (HClO). It is obtained by the Pelus method by the interaction of mercury oxide with gaseous chlorine according to one of the reaction equations: 2Cl2 + 2HgO → Cl2O + Hg2OCl2 or 2Cl2 + HgO → Cl2O + HgCl2. The conditions for these reactions are different. Chlorine oxide (I) is condensed at a temperature of minus 60 ° C, because at a higher temperature it decomposes, exploding, and in a concentrated form is explosive. An aqueous solution of Cl2O is obtained by chlorination in water of alkaline earth or alkali metal carbonates. The oxide is highly soluble in water, and hypochlorous acid is formed: Cl2O + H2O ↔ 2HClO. In addition, it also dissolves in carbon tetrachloride.
Chlorine oxide with an oxidation state of +4 is otherwise called dioxide. This substance is soluble in water, sulfuric and acetic acids, acetonitrile, carbon tetrachloride, as well as in other organic solvents, with an increase in the polarity of which its solubility increases. Under laboratory conditions, it is obtained by the interaction of potassium chlorate with oxalic acid: 2KClO3 + H2C2O4 → K2CO3 + 2ClO2 + CO2 + H2O. Since chlorine (IV) oxide is an explosive substance, it cannot be stored in solution. For these purposes, silica gel is used, on the surface of which ClO2 can be stored in an adsorbed form for a long time, at the same time it is possible to get rid of chlorine impurities polluting it, since it is not absorbed by silica gel. Under industrial conditions, ClO2 is obtained by reduction with sulfur dioxide, in the presence of sulfuric acid, sodium chlorate: 2NaClO3 + SO2 + H2SO4 → 2NaHSO4 + 2ClO2. It is used as a bleach, for example, paper or cellulose, etc., as well as for sterilization and disinfection of various materials.
Chlorine oxide with an oxidation state of +6, when melted, decomposes according to the reaction equation: Cl2O6 → 2ClO3. Chlorine (VI) oxide is obtained by oxidizing dioxide with ozone: 2O3 + 2ClO2 → 2O2 + Cl2O6. This oxide is able to interact with alkali solutions and with water. In this case, disproportionation reactions occur. For example, when interacting with potassium hydroxide: 2KOH + Cl2O6 → KClO3 + KClO4 + H2O, the result is potassium chlorate and perchlorate.
Higher chlorine oxide is also called chlorine anhydride or dichloroheptoxide is a strong oxidizing agent. It is capable of exploding from shock or when heated. However, this substance is more stable than oxides with oxidation states of +1 and +4. Its decomposition to chlorine and oxygen is accelerated due to the presence of lower oxides and with increasing temperature from 60 to 70 ° C. Chlorine oxide (VII) is able to slowly dissolve in cold water, as a result of the reaction perchloric acid is formed: H2O + Cl2O7 → 2HClO4. Dichloroheptoxide is obtained by carefully heating perchloric acid with phosphoric anhydride: P4O10 + 2HClO4 → Cl2O7 + H2P4O11. Cl2O7 can also be obtained using oleum instead of phosphoric anhydride.
The section of inorganic chemistry, which studies halogen oxides, including chlorine oxides, has begun to develop actively in recent years, since these compounds are energy-intensive. They are able to give energy instantly in the combustion chambers of jet engines , and in chemical current sources the speed of its return can be regulated. Another reason of interest is the possibility of synthesizing new groups of inorganic compounds, for example, chlorine oxide (VII) is the ancestor of perchlorates.