Carbon monoxide (CO) is a colorless, odorless, and tasteless gas that is slightly less dense than air. It is toxic to humans and animals when encountered in higher concentrations. Every year, at least 430 people die in the U. S. from accidental CO poisoning. It is also produced in normal animal metabolism in low quantities. In the atmosphere, it has a role in the formation of ground-level ozone.
Carbon monoxide consists of one carbon atom and one oxygen atom, connected by a triple bond that consists of two covalent bonds as well as one dative covalent bond. Since four of the shared electrons come from the oxygen atom and only two from carbon, one bonding orbital is occupied by two electrons from oxygen, forming a dative or dipolar bond. This causes a C ← O polarization of the molecule, with a small negative charge on carbon and a small positive charge on oxygen.
How is it produced?
Carbon monoxide is produced from the partial oxidation of carbon-containing compounds. It forms when there is not enough oxygen to produce carbon dioxide (CO2), such as when operating a stove or engine in an enclosed space. In the presence of oxygen, including atmospheric concentrations, carbon monoxide burns with a blue flame, producing carbon dioxide. Coal gas, which was widely used before the 1960s for domestic lighting, cooking, and heating, had carbon monoxide as a significant fuel constituent.
Natural sources of CO include volcanoes, forest fires, and other forms of combustion.
History
Aristotle first recorded that burning coals produced toxic fumes. An ancient method of execution was to shut the criminal in a room with flaming coals. Mechanism of death was not known.
Greek physician Galen speculated that there was a change in the composition of the air that caused harm when inhaled. In 1776, the French chemist de Lassone produced CO by heating zinc oxide with coke, but mistakenly concluded that the gaseous product was hydrogen, as it burned with a blue