Syn-propanethial-S-oxide
Encyclopedia
syn-Propanethial S-oxide (C3H6OS) is a gas that acts as a lachrymatory agent
(triggers tearing and stinging on contact with the eyes). The chemical is released from onions, Allium cepa, as they are sliced. The release is due to the breaking open of the onion cells and their releasing enzymes called alliinase
s, which then break down amino acid
sulfoxide
s, generating sulfenic acid
s. A specific sulfenic acid, 1-propenesulfenic acid, formed when onions are cut, is rapidly rearranged by a second enzyme, called the lachrymatory factor synthase or LFS, giving syn-propanethial S-oxide. The gas diffuses through the air and, on contact with the eye, it stimulates sensory neurons creating a stinging, painful sensation. Tears are released from the tear glands to dilute and flush out the irritant. Recently, a structurally related lachrymatory compound, syn-butanethial S-oxide, C4H8OS, has been found in another genus Allium plant, Allium siculum.
Lachrymatory agent
Tear gas, formally known as a lachrymatory agent or lachrymator , is a non-lethal chemical weapon that stimulates the corneal nerves in the eyes to cause tears, pain, and even blindness...
(triggers tearing and stinging on contact with the eyes). The chemical is released from onions, Allium cepa, as they are sliced. The release is due to the breaking open of the onion cells and their releasing enzymes called alliinase
Alliinase
In enzymology, an alliin lyase is an enzyme that catalyzes the chemical reactionHence, this enzyme has one substrate, S-alkyl-L-cysteine S-oxide, and two products, alkyl sulfenate and 2-aminoacrylate....
s, which then break down amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
sulfoxide
Sulfoxide
A sulfoxide is a chemical compound containing a sulfinyl functional group attached to two carbon atoms. Sulfoxides can be considered as oxidized sulfides...
s, generating sulfenic acid
Sulfenic acid
A sulfenic acid is an organosulfur compound and oxoacid with the general formula RSOH, where R ≠ H. Simple sulfenic acids, such as methanesulfenic acid, CH3SOH, are highly reactive and cannot be isolated in solution. In the gas phase the lifetime of methanesulfenic acid is about one minute...
s. A specific sulfenic acid, 1-propenesulfenic acid, formed when onions are cut, is rapidly rearranged by a second enzyme, called the lachrymatory factor synthase or LFS, giving syn-propanethial S-oxide. The gas diffuses through the air and, on contact with the eye, it stimulates sensory neurons creating a stinging, painful sensation. Tears are released from the tear glands to dilute and flush out the irritant. Recently, a structurally related lachrymatory compound, syn-butanethial S-oxide, C4H8OS, has been found in another genus Allium plant, Allium siculum.