propanethial S-oxide

'''syn-Propanethial S-oxide (or (Z)-propanethial S-oxide'), a member of a class of organosulfur compounds known as thiocarbonyl S''-oxides (formerly "sulfines"), is a volatile liquid that acts as a lachrymatory agent (triggers tearing and stinging on contact with the eyes).

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Onion release
Related compounds
References

'''syn-Propanethial S-oxide (or (Z)-propanethial S-oxide'), a member of a class of organosulfur compounds known as thiocarbonyl S-oxides (formerly "sulfines"), is a volatile liquid that acts as a lachrymatory agent (triggers tearing and stinging on contact with the eyes).

==Onion release== The chemical is released from onions, Allium cepa, as they are sliced. The release is due to the breaking open of the onion cells, which releases enzymes called alliinases. Alliinases then break down amino acid sulfoxides, generating sulfenic acids. A specific sulfenic acid, allicin or 1-propenesulfenic acid, is rapidly rearranged by another enzyme, the lachrymatory factor synthase (LFS), to give syn-propanethial S-oxide. Vapors from this volatile liquid induce tearing.