Chlorate
The chlorate anion has the formula ClO3−. In this case, the chlorine atom is in the +5 oxidation state. "Chlorate" can also refer to chemical compounds containing this anion; chlorates are the salts of chloric acid. "Chlorate", when followed by a roman numeral in parenthesis, e.g. chlorate(VII), refers to a particular oxyanion of chlorine.
As predicted by VSEPR, chlorate anions have trigonal pyramidal structures.
Chlorates are powerful oxidizers and should be kept away from organics or easily oxidized materials. Mixtures of chlorate salts with virtually any combustible material (sugar, sawdust, charcoal, organic solvents, metals, etc) will readilly deflagrate. Chlorates were once widely used in pyrotechnics for this reason, though their use has fallen due to their instability. Most pyrotechnic applications which formerly used chlorates in the past now use perchlorates instead.
Structure and bonding
The chlorate ion cannot be satisfactorily represented by just one Lewis structure, since all the Cl-O bonds are the same length (1.49 Å in potassium chlorate[1]), and the chlorine atom is hypervalent. Instead, it is often thought of as a hybrid of multiple resonance structures:
Preparation
Laboratory
Metal chlorates can be prepared by adding chlorine to hot metal hydroxides like KOH:
- 3 Cl2 + 6 KOH → 5 KCl + KClO3 + 3 H2O
In this reaction chlorine undergoes disproportionation, both reduction and oxidation. Chlorine, oxidation number 0, forms chloride Cl− (oxidation number −1) and chlorate(V) ClO−
3 (oxidation number +5). Reaction of dilute aqueous sodium hydroxide with chlorine produces the chloride and hypochlorite (oxidation number +1).
Industrial
The industrial scale synthesis for sodium chlorate starts from aqueous sodium chloride solution (brine) rather than chlorine gas. If equipment for electrolysis does not prevent a mixing of the chlorine and the sodium hydroxide is as described in chlorine, then the disproportionation reaction described above occurs. The heating of the reactants to 50-70°C is performed by the electrical power used for electrolysis.[citation needed]
Compounds (salts)
Examples of chlorates include
- potassium chlorate, KClO3
- sodium chlorate, NaClO3
- magnesium chlorate, Mg(ClO3)2
Other oxyanions
If a Roman numeral in brackets follows the word "chlorate", this indicates the oxyanion contains chlorine in the indicated oxidation state, namely:
| Common name | Stock name | Oxidation state | Formula |
|---|---|---|---|
| Hypochlorite | Chlorate(I) | +1 | ClO− |
| Chlorite | Chlorate(III) | +3 | ClO2− |
| Chlorate | Chlorate(V) | +5 | ClO3− |
| Perchlorate | Chlorate(VII) | +7 | ClO4− |
Using this convention, "chlorate" means any chlorine oxyanion. Commonly, "chlorate" refers only to chlorine in the +5 oxidation state.\
Toxicity
Chlorates are relatively toxic, though they form generally harmless chlorides upon reduction.
References
- ^ J. Danielsen, A. Hazell, F. K. Larsen (1981). "The structure of potassium chlorate at 77 and 298 K". Acta Cryst. B37: 913–915. doi:10.1107/S0567740881004573.
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