Syn-propanethial-S-oxide

Syn-propanethial-S-oxide is a volatile sulfur compound that acts as a lachrymatory agent, which is a type of chemical compound that causes the eyes to produce tears without causing harm. This compound is best known for its role in the common kitchen experience of tearing up when slicing onions. Syn-propanethial-S-oxide is produced when the cells of the onion are damaged, leading to a chemical reaction that releases this compound into the air.

Production

When an onion is cut, the damage to its cells causes the enzyme alliinase to convert the amino acid isoalliin into various sulfur-containing compounds. Among these, syn-propanethial-S-oxide is formed through a series of reactions involving the conversion of propenyl sulfenic acids by the enzyme LF synthase. This compound is highly volatile, meaning it readily evaporates at room temperature, allowing it to reach the eyes where it stimulates the sensory neurons, causing a burning sensation followed by tears.

Effects

The primary effect of syn-propanethial-S-oxide is its ability to stimulate the eyes to produce tears. This is a defensive response to the irritation of the sensory neurons in the eyes. The compound itself is not harmful and does not cause damage to the eye tissues. Its lachrymatory effect is purely a mechanical response to the irritation.

Applications

While primarily known for its unintended effect in cooking, research into syn-propanethial-S-oxide has explored its potential applications in various fields. Its strong lachrymatory properties have led to investigations into its use as a non-lethal tear gas for crowd control or personal defense. However, its use in such applications is limited by the ease with which it can be produced and controlled.

Safety and Handling

Handling onions and other substances that can release syn-propanethial-S-oxide requires minimal safety precautions. Common methods to reduce exposure include cutting onions under running water, chilling the onions before cutting to reduce the volatility of the compound, or using a sharp knife to minimize cell damage. These methods do not eliminate exposure but can significantly reduce the concentration of syn-propanethial-S-oxide in the air, thereby minimizing its irritating effects.

See Also

• Lachrymatory agent
• Alliinase
• Sulfur compounds
• Onions