Silicones – Organic or Inorganic Compounds?

In terms of chemical structure, silicones are somewhere between typically organic and typically inorganic compounds.
All carbon compounds, with the exception of carbon dioxide, carbon monoxide, carbonic acid and carbonates, are considered organic.
Some of their distinguishing characteristics are relatively low melting points and relatively low decomposition temperatures. In nature, they are found in living organisms and in substances of biological origin, for example petroleum. Until F. Wöhler synthesized urea in 1828, the prevailing opinion was that it was impossible to make organic carbon compounds by a synthetic route. This ability was described exclusively to a mysterious natural life force (vis vitalis). The exchange in opinion that resulted from Wöhler’s synthesis saw a rapid surge in organic chemistry in just a few decades. While in the year 1830, only about 3,000 organic compounds were known, this figure had grown to 300,000 by 1930 and to 1.2 million by 1950. In 2001, the figure exceeded 15,000,000 and is increasing at a rate of about 500,000 each year. The fact that that there are millions of different organic compounds is due to the ability of carbon atoms to form stable carbon-carbon bonds (both single and multiple).

Unlike carbon, silicon shows no tendency to form Si-Si bonds or even Si chains. The most common silicon compound is silicon dioxide or SiO₂ (quartz, sand) which, unlike carbon dioxide CO₂, occurs not as molecules, but as a covalent crystal in which a great many Si-O-Si bonds form a crystal lattice (the quartz lattice). Quartz is one of the most thermally and chemically resistant of all compounds. The high bond energy of the Si-O-Si linkages renders it extremely resistant to chemicals and highly unreactive.
Silicones have the structure of a quartz that has been modified with organic groups. They feature typical organic and inorganic properties. A key property is the high resistance of the quartz backbone toward any kind of external influence. Silicone products range from liquids (silicone fluids) through to solid compounds (silicone resins, silicone rubber).