Permanganic acid

Permanganic acid is a chemical compound with the formula HMnO_. It is a strong acid and a powerful oxidizing agent. Permanganic acid is the parent compound of permanganate salts, such as potassium permanganate.

Structure and Properties

Ball-and-stick model of permanganic acid

Permanganic acid is a tetrahedral molecule, with the central manganese atom surrounded by four oxygen atoms. The manganese atom is in the +7 oxidation state, which is the highest oxidation state for manganese. This high oxidation state is responsible for the strong oxidizing properties of permanganic acid.

Permanganic acid is typically a deep purple color in solution, similar to its salts. It is unstable in pure form and is usually encountered in aqueous solution.

Preparation

Permanganic acid can be prepared by the reaction of a permanganate salt with a strong acid. For example, the reaction of potassium permanganate with sulfuric acid can produce permanganic acid:

KMnO_ + H_SO_ _ HMnO_ + KHSO_

This reaction must be carried out carefully, as permanganic acid is unstable and can decompose, releasing oxygen gas.

Reactions

Permanganic acid is a strong oxidizing agent and can react with a variety of organic and inorganic compounds. It can oxidize alcohols to carboxylic acids, and it can also oxidize sulfides to sulfates.

In acidic solutions, permanganic acid can be reduced to manganese dioxide (MnO_), which is a brown solid:

2 HMnO_ + 3 H_O_ _ 2 MnO_ + 3 O_ + 4 H_O

Stability

Permanganic acid is not stable in concentrated form and tends to decompose, especially in the presence of light or heat. It is more stable in dilute solutions, where it can exist for a short period before decomposing.

Applications

While permanganic acid itself is not commonly used due to its instability, its salts, such as potassium permanganate, are widely used in chemistry and medicine. Potassium permanganate is used as a disinfectant, in water treatment, and as an oxidizing agent in various chemical reactions.

Related pages

• Potassium permanganate
• Manganese dioxide
• Oxidizing agent