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Nobel Prize in Chemistry 2026 · Classroom handout

They showed how chemistry can pick one mirror-image form of a molecule and amplify it.

Henri B. Kagan, Kenso Soai · “for the discovery of non-linear effects and autocatalysis in asymmetric organic synthesis”

The quick version

  1. Many molecules come in left and right mirror forms, and life uses only one form.
  2. Kagan found that mismatched left-right catalyst pairs work slowly, so the majority form wins more than expected.
  3. Soai made a molecule that copies itself, turning a tiny chance imbalance into a nearly pure product.

Picture it

The copy machine that jams its rival. Picture a room of copy machines that can only print new copy machines. Left-handed machines print left-handed machines, right-handed ones print right-handed ones, and whenever a left and a right machine get paired up, they jam each other and stop. Start with just one or two more left machines than right ones, and the jams remove the right machines first, so the left side takes over the room. The analogy breaks because molecules make no choices: the takeover comes from reaction speeds and chance, and chemists still debate exactly how the 'jam' works at the atomic level.

For younger students

Some tiny building blocks come in left-handed and right-handed versions, like gloves. Living things only use one kind. These scientists found a way for the gloves to copy themselves so that a few extra left gloves turn into a whole pile of left gloves.

A 10-minute lesson

Minutes 0 to 2, opening question. Hold up both hands and ask, 'Are these the same?' Let students argue, then show that you cannot stack one hand exactly on the other. Introduce the word chiral and explain that many molecules, such as amino acids, are chiral and life uses only one form.

Minutes 2 to 7, hands-on demo. Put 6 light beans (left) and 4 dark beans (right) in a cup. Students draw two beans at a time. A matching pair goes back with one extra bean of that color, which stands for copying. A mixed pair goes aside, which stands for jamming. After a few rounds, the light beans take over.

Minutes 7 to 9, connect to the real science. Henri Kagan found in 1986 that mixed left-right catalyst pairs work slowly. Kenso Soai built a molecule that copies itself, and in one test a 0.00005% lead grew past 99.5% in three rounds. Point out where the beans mislead. Molecules make no choices, and chemists still debate exactly how the jam works.

Minutes 9 to 10, check for understanding. Ask, 'If we start with equal beans, which color wins?' Listen for answers about chance. Then share that in 37 Soai runs with no deliberate imbalance, one form won 18 times and the other won 19.

Words to know

Chiral
Having a mirror image you cannot stack on top of the original, like a left and right hand.
Enantiomers
The two mirror-image forms of a chiral molecule.
Homochiral
All of one hand. Greek for 'same hand.' Life's amino acids and sugars are homochiral.
Racemic mixture
A 50-50 mix of both mirror forms, which ordinary reactions produce.
Enantiomeric excess (ee)
How much more of one form there is than the other, as a percentage.

Check for understanding

  1. What did Kagan show about a catalyst made from an uneven mix of both mirror forms?
    1. Its product can be purer than a straight-line rule predicts
    2. Its product is always exactly as pure as the catalyst
    3. It stops working as soon as both forms are present
    4. It always gives a 50-50 mix of the product
  2. Soai's 1990 reaction copied itself, yet purity fell each round. What changed in his 1995 reaction?
    1. Each round came out purer than the catalyst that made it
    2. He stopped using a catalyst at all
    3. He used light to pick out one form
    4. The reaction made only one form from the very first step
  3. Soai ran the reaction 37 times with no deliberate imbalance. What does the result show?
    1. Chance picks the winner, so each form wins about half the time
    2. The left form always wins, just as in living things
    3. Nothing happens, and the product stays a 50-50 mix
    4. It proves how life on Earth became one-handed

Answer key: 1a, 2a, 3a.

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