Carbon monoxide (CO) is a colorless, odorless, tasteless, and flammable gas slightly less dense than air. It's poisonous to humans and animals because it interferes with the delivery of oxygen to the body's organs and tissues. Composed of one carbon atom and one oxygen atom linked by a triple bond, CO is the simplest carbon oxide. Known as carbonyl when acting as a ligand in coordination complexes, CO plays a crucial role in various industrial chemical processes.
1950: CO Ligand Binding and Infrared Spectrum
Around 1950, the understanding of CO as a ligand in metal complexes developed. Scientists discovered how CO binds through carbon, forming a quasi-triple bond, and how this affects the infrared spectrum of these complexes. The absorption shift in the infrared spectrum from free CO (2143 cm-1) to CO in metal complexes (near 1950 cm-1) became a key indicator of such bonding.
1970: Interstellar CO Detection
In 1970, carbon monoxide (CO) was detected in interstellar space using radio telescopes. This discovery was significant because CO is much easier to detect than molecular hydrogen (H2), the most common molecule in space, and thus serves as a useful tracer for molecular gas clouds where stars form.
1989: Phosgene Production
In 1989, global phosgene production reached an estimated 2.74 million tonnes. Phosgene is produced by reacting purified carbon monoxide and chlorine gas over activated carbon and plays an essential role in the manufacture of isocyanates, polycarbonates, and polyurethanes.
1993: CO as a Neurotransmitter
In 1993, carbon monoxide was identified as a neurotransmitter. This discovery led to significant clinical interest in CO's role as a biological regulator, marking a turning point in understanding its function beyond a toxic gas.
2002: FDA GRAS Status for CO in Packaging
In 2002, the U.S. Food and Drug Administration (FDA) granted "generally recognized as safe" (GRAS) status to carbon monoxide for use as a secondary packaging system. This meant CO could be used without specific labeling requirements.
2004: FDA Approval for CO as Primary Packaging
In 2004, the FDA further approved carbon monoxide as a primary packaging method. This decision was based on the finding that CO does not mask food spoilage odors, broadening its use in food packaging. However, this process is not universally authorized, with countries like Japan, Singapore, and those in the European Union not adopting it.
2006: Organometallics Publication
In 2006, the book "Organometallics" by C. Elschenbroich was published. This book details the robust nature of metal carbonyl complexes, especially when the metal is in lower oxidation states, with examples like iron pentacarbonyl and nickel carbonyl.