How many chiral centers are present in the open-chain form of fructose?

### Why this is right Open-chain fructose is a six-carbon ketose. Its carbonyl carbon and terminal carbon atoms are not chiral, leaving three internal carbons with four different substituents. ### The other options - **Two**: this misses one stereogenic carbon in the open-chain structure. - **Four**: this incorrectly counts a carbonyl carbon or a terminal carbon as chiral. - **One**: this counts too few of the stereogenic centers. ### Terms - **Ketose**: a sugar containing a ketone carbonyl group. - **Chiral center**: an atom, usually carbon, attached to four different substituents. ### Remember For open-chain sugars, count the tetrahedral carbons with four different attachments.