Perchloric Oxide (cl2o7): Formula, Properties, Risks

The perchloric oxide , also called chlorine oxide (VII), anhydride or perchloric dichloro heptoxide,  is an inorganic chemical compound of formula Cl 2 O7. Its structure is presented in figure 1.

ANDIt is one of the most stable chlorine oxides and reacts with water to produce perchloric acid: Cl 2 O 7 + H 2 O D 2HClO 4.

The compound is obtained by careful dehydration of perchloric acid with phosphorous pentoxide at -10 ° C.

2HClO 4 + P 2 O 5 »Cl 2 O 7 + 2HPO 3

The compound is distilled to separate it from metaphosphoric acid with considerable caution given its explosive nature. It can also be formed by lighting in mixtures of chlorine and ozone.

Physical and chemical properties of perchloric oxide

Chlorine oxide (VII) is a colorless, volatile and oily liquid. Its molecular weight is 182.9 g / mol, its density is 1900 kg / m3, and its melting and boiling points are -91.57 ºC and 82 ºC respectively.

It is spontaneously explosive on impact or in contact with the flame and especially in the presence of its decomposition products.

Chlorine heptoxide dissolves in carbon tetrachloride at room temperature and reacts with water to form perchloric acid. It explodes on contact with iodine.

Under normal conditions, it is more stable, although with less oxidizing power than the other chlorine oxides. For example, it does not attack sulfur, phosphorus or paper when it is cold.

Dichloro heptoxide is a strongly acidic oxide, and in solution it forms an equilibrium with perchloric acid. Forms perchlorates in the presence of alkali metal hydroxides.

Its thermal decomposition is produced by the monomolecular dissociation of chlorine trioxide and radical

Reactivity and hazards

Perchloric oxide is an unstable compound. It decomposes slowly on storage, with the production of colored decomposition products that are lower chlorine oxides.

It is spontaneously explosive, especially in the presence of its decomposition products, incompatible with reducing agents, strong acids and bases. 

Although it is the most stable chlorine oxide, Cl 2 O 7 is a strong oxidant, as well as an explosive that can be quenched by flame or mechanical shock, or by contact with iodine.

However, it is less oxidizing than the other chlorine oxides, and does not attack sulfur, phosphorus, or paper when cold. Has the same effects on the human body as elemental chlorine, and requires the same precautions

Ingestion causes severe burns to the mouth, esophagus, and stomach. Vapor is very toxic by inhalation.

In case of contact with the eyes, check whether you are wearing contact lenses and remove them immediately. Eyes should be flushed with running water for at least 15 minutes, keeping the eyelids open. Cold water can be used. Eye ointment should not be used.

If the chemical comes into contact with clothing, remove it as quickly as possible, protecting your own hands and body. Place the victim under a safety shower.

If the chemical accumulates on the victim’s exposed skin, such as hands, the contaminated skin is gently and carefully washed with running water and non-abrasive soap.

Cold water can be used. If irritation persists, seek medical attention. Wash the contaminated clothing before using it again.

In case of inhalation, the victim should be allowed to rest in a well-ventilated area. If inhalation is severe, the victim should be evacuated to a safe area as soon as possible.

Loosen tight clothing such as a collar, belt, or tie. If it is difficult for the victim to breathe, oxygen should be administered.

If the victim is not breathing, mouth-to-mouth resuscitation is performed. Always keeping in mind that it may be dangerous for the person providing aid to give mouth-to-mouth resuscitation when the inhaled material is toxic, infectious, or corrosive.

In all cases, seek immediate medical attention.


Perchloric oxide has no practical applications. It could be used as an oxidizing agent or for the production of perchloric acid but its explosive nature makes it difficult to handle.

Dichloroheptoxide can be used as a reagent for the production of perchlorates or for the study with different reactions.

In the work of Kurt Baum, the reactions of perchloric oxide with olefins (Baum, 1976), alcohols (Kurt Baum, Reactions of dichlorine heptoxide with alcohols, 1974), alkyl iodides and acyl perchlorate with ester (Kurt Baum, 1975) obtaining halogenations and oxidations.

In the case of alcohols, it produces alkyl perchlorates by reacting with simple alcohols such as ethylene glycol, 1,4-butadienol, 2, 2, 2-trifluoroethanol, 2, 2-dinitropropanol. Reacts with 2-propanol to give isopropyl perchlorate. 2-hexanol and 3-hexanol give unarranged perchlorates and their respective ketones.

Propene reacts with dichloro heptoside in carbon tetrachloride to give isopropyl perchlorate (32%) and 1-chloro, 2-propylperchlorate (17%). The compound reacts with cis -butene to give 3-chlorobutyl perchlorate (30%) and 3-keto, 2-butyl perchlorate (7%).

Dichloro heptoxide reacts with primary and secondary amines in carbon tetrachloride solution to give N-perchlorates:

2 RNH2 + Cl2O7 → 2 RNHClO3 + H2O

2 R2NH + Cl2O7 → 2 R2NClO3 + H2O

It also reacts with alkenes to give alkyl perchlorates. For example, it reacts with propene in carbon tetrachloride solution to produce isopropyl perchlorate and 1-chloro-2-propyl perchlorate (Beard & Baum, 1974).


  1. Baum, K. (1976). Reactions of dichlorine heptoxide with olefins. Org. Chem. 41 (9) , 1663-1665.
  2. Beard, CD, & Baum, K. .. (1974). Reactions of dichlorine heptoxide with amines. Journal of the American Chemical Society. 96 (10) , 3237-3239.
  3. Egon Wiberg, NW (2001). Inorganic Chemistry. Academic Press: London.
  4. EMBL-EBI. (2009, April 25). dichlorine heptaoxide . Retrieved from ChEBI:
  5. Kurt Baum, CD (1974). Reactions of dichlorine heptoxide with alcohols. Am. Chem. Soc., 96 (10) , 3233-3237.
  6. Kurt Baum, CD (1975). Reactions of dichlorine heptoxide and of acyl perchlorates with ethers. Org. Chem., 40 (1) , 81-85.
  7. Kurt Baum, CD (1975). Reactions of dichlorine heptoxide and of hypohalites with alkyl iodides. Org. Chem., 40 (17) , 2536-2537.
  8. Royal Society of Chemistry. (2015). Dichlorine heptoxide . Retrieved from chemspider:

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