Which chemical in onion make our eyes crying?​

The synthase enzyme which is present in onions causes tears in our eyes.

Answer:

syn-propanethial-S-oxide

Explanation:

Onions produce the chemical irritant known as syn-propanethial-S-oxide. It stimulates the eyes' lachrymal glands so they release tears. Scientists used to blame the enzyme allinase for the instability of substances in a cut onion.