Chlorate

The chlorate ion

Structure and bonding in the chlorate ion

The chlorate anion has the formula ClO-
3. 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 parentheses, 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 readily 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 the more stable perchlorates instead.

See also: Category:Chlorates

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 cold aqueous metal hydroxides with chlorine produces the chloride and hypochlorite (oxidation number +1) instead.

Industrial

The industrial scale synthesis for sodium chlorate starts from aqueous sodium chloride solution (brine) rather than chlorine gas. If equipment for electrolysis allows mixing of the chlorine and the sodium hydroxide, 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- 1
Chlorite	Chlorate(III)	+3	ClO- 2
Chlorate	Chlorate(V)	+5	ClO- 3
Perchlorate	Chlorate(VII)	+7	ClO- 4

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

1. ^ 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.