Answer: Syn-Propanethial-S-oxide
Notes: When an onion is sliced the onion's cells release syn-Propanethial-S-oxide which stimulates the eyes’ lachrymal glands to release tear. “Sunions” are tearless sweet onions which are increasingly available in markets of USA and UK. These onions are produced by breeding a variety of onions by which, the chemicals responsible for inducing tears diminish over a period of time.
