The chopping of an onion makes one cry because of the chemical containing

When an onion is sliced or chopped, its cells break down, releasing enzymes called alliinases that react with amino acid sulfoxides to produce sulfenic acids. These acids rearrange to form a volatile gas known as syn-propanethial-S-oxide, which contains sulphur. When this gas hits the moisture of our eyes, it stimulates sensory neurons and activates the lachrymal glands to produce tears.