What is the relationship between chemistry and the tears that come when we cut onions? The chemistry is involved from the smell to the reaction it causes in our eyeballs, the onion has several chemicals that stimulate our smell, taste and unfortunately our eyes.
Let's start with the smell, which compound is responsible for that delicious smell of fried onion in butter? These are sulfur oxides derived from sulfuric acid (H2ONLY4).
Now to explain about tears we need to go a little further. When we cut an onion, it releases enzymes called allinases, which in turn react with the sulfuric oxide already present in the structure of the onion. The reaction gives rise to sulfinic acid which, as it is not very stable, ends up turning into a volatile gas.
The gas obtained in the reaction to volatilize reaches the eyes causing an unpleasant reaction in the nerve endings of the cornea, and to defend itself these terminals activate the lacrimal glands, which in turn release the tears: the time of cry!
There are several ways to prevent this annoyance, one of them is to cut the onions using the fan. Turn on a fan on its side and facing the onion so that the gas does not reach your eyes, do the test and see what was exposed here.
Do not stop now... There's more after the advertising ;)
By Líria Alves
Graduated in Chemistry
See more!
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Would you like to reference this text in a school or academic work? Look:
SOUZA, Líria Alves de. "Onion and Tears: Chemistry Explains"; Brazil School. Available in: https://brasilescola.uol.com.br/quimica/cebola-lagrimas-quimica-explica.htm. Accessed on June 27, 2021.
