How does oxygen break down in oxidizing agents

Decomposition (chemistry)

decomposition (or Dismantling, degradation) in chemistry and biology means the breakdown of a chemical compound into smaller molecules or even the elements through physical, chemical or biological influences. Therefore one differentiates the physical decomposition or. thermal decomposition, the chemical decomposition and the biological decomposition or the biodegradation.

Types of decomposition

Physical decomposition

A chemical substance often decomposes when energy is supplied in the form of heat (see pyrolysis). That is why it is also known as thermal decomposition. Other energy sources such as electricity (electrolysis, Lightning bolts, Electric arc), Ultraviolet radiation (Photolysis) or X-rays cause bonds within molecules to split. This often creates radicals, which then continue to react as unstable, high-energy particles. With the exclusion of oxidizing agents such as atmospheric oxygen, this decomposition can take place down to the elements from which the compound is built (e.g. formation of coal deposits) or to compounds that are thermodynamically most stable under the selected conditions. In synthetic chemistry, the decomposition of starting materials under low pressure and high temperatures to a desired end product is used as a "flash vacuum pyrolysis" process.

Examples
$ \ mathrm {CH_4 \ \ xrightarrow {\ Delta T} \ C + \ 2 \ H_2} $
Thermal decomposition of methane to carbon and hydrogen
$ \ mathrm {2 \ BaO_2 \ \ xrightarrow {\ Delta T} \ 2 \ BaO + \ O_2} $
Thermal decomposition of barium peroxide to barium oxide and oxygen
$ \ mathrm {2 \ H_2O \ \ xrightarrow {Electrolysis} \ O_2 \ + \ 2 \ H_2} $
Electrolysis of water to oxygen and hydrogen

Chemical decomposition

If oxidizing agents are present during decomposition, the most stable compounds with the oxidizing agent are created from combustible substances under combustion, sometimes even without energy input. If the oxidizing agent is oxygen (e.g. from the air), organic compounds produce water H2O and carbon dioxide CO2 (possibly also sulfur oxides, nitrogen oxides or nitrogen as gas), in the case of inorganic substances mostly oxides or other oxygen-containing compounds such as sulfates, phosphates or silicates.

Some compounds also decompose when heated, releasing stable compounds such as carbon dioxide (Decarboxylation) or water (Dehydration, e.g. the release of the crystal water Hydrates). If metals are attacked during decomposition, this is called corrosion; in the case of iron, in particular, the resulting product from various iron oxides and water is called rust. When biologically important, polymeric biomolecules such as proteins and polysaccharides are broken down by enzymes, diluted acids or bases, one speaks of hydrolysis (Decomposition by water). The breakdown products of a substance can provide information about the composition of the starting substances. The thermal degradation therefore plays an important role in analytical chemistry.

Examples
$ \ mathrm {CH_4 \ + \ 2 \ O_2 \ \ xrightarrow {\ Delta T} \ CO_2 \ + \ 2 \ H_2O} $
Combustion of methane with oxygen to produce carbon dioxide and water
$ \ mathrm {HOOC-CH_2-COOH \ \ xrightarrow {\ Delta T} \ HOOC-CH_3 \ + \ CO_2} $
Thermal decomposition of malonic acid to acetic acid with elimination of carbon dioxide

Biological decomposition

Living beings that break down organic substances are grouped under the name saprobionts or destructors. These are animals such as mites, woodlice, and microorganisms such as bacteria (e.g. actinomycetes) and fungi. Organic substances, mostly high-polymer proteins or carbohydrates, are first removed from these organisms mechanically, then chemically either with the exclusion of air (anaerobic) or air presence (aerobic) decomposes. The saprobionts use the organic compounds as an energy source.

At complete mineralization When the polymers are broken down by enzymes from the hydrolase class, monomers such as amino acids and monosaccharides are first formed. These are then completely broken down into carbon dioxide, water, ammonium compounds and nitrates. If the conditions are not optimal, only high-molecular humic substances are still formed.[1]

Biodegradation

Badges of DIN CERTCO and European Bioplastics according to EN 13432

The decomposition of organic substances by saprobionts or their enzymes, which feed waste into the natural material cycle, is also becoming general biodegradation called. The biodegradability of industrially produced chemicals, including those based on renewable raw materials such as in oleochemicals, and materials (e.g. plastics) is examined using (in some cases) specific test procedures. Labeling systems exist, especially for biodegradable plastics. Often the terms Biodegradability or Biodegradability used.

Substances are called resistant to degradation if they are not subject to biodegradation. If they are also not broken down by other chemical or physical processes, they are referred to as persistent.

See also

Web links

Individual evidence

  1. ↑ Science online lexicons: Entry on decomposition in the compact lexicon of chemistry, accessed September 28, 2008.