Which chemical compound in onion causes tears in the eyes?

Options

  • A. Formic acid
  • B. Syn-propanethial-S-oxide
  • C. Acetic acid
  • D. More than one of the above
  • E. None of the above

Correct Answer (Detailed Explanation is Below)

B. Syn-propanethial-S-oxide

Detailed Explanation

Syn-propanethial-S-oxide is the lachrymatory factor responsible for onion-induced tears. Cutting onion damages its cells and allows enzymes to react with sulfur-containing compounds, ultimately producing this volatile compound. It irritates the eyes and stimulates tear production. Important related terms include lachrymator, sulfur compounds, enzymes and volatile compounds.