When we cut onions, we break the cells releasing all their contents making amino acids sulfoxides form sulfenic acids. The enzymes that were separated are now able to mix with the sulfenic acids, thus producing propanethiol S-oxide. Propanethiol S-oxide is a volatile sulfur compound that noves upwards to our eyes. The gas reacts with the water in our eyes. Certain chemical changes take place in the eyes and there is the formation sulfuric acid. This sulfuric acid burns your eyes releasing tears to wash the irritating substance away. One way in which we can prevent the tearing of our eyes is by keeping it cool in a refrigerator before taking it out to cut it. this slows down the reactions and changes the chemistry in the onion. Another way of avoiding the tearing of the eyes is by cutting the onion under running water. Lastly, when cutting an onion, avoid the roots as it has a higher concentration of enzymes.