Imagine with me a compound with 6 C atoms, arranged linearly — not branched and not in a ring.

At one end there is an aldehyde group (call this carbon atom 1). All the other carbon atoms carry OH groups — they are, then, alcohol functional groups, 5 of them.

Suppose that the OH on C5 reacts with the aldehyde on C1. Which of the following describes the product of this reaction best?

A. An ester is formed and a ring created in the process.

B. An anhydride is formed and a ring created in the process.

C. A reaction of this sort cannot occur. There is nothing in our course, so far, that indicates that it can occur.

D. A hemiacetal is formed; a ring is formed having 6 atoms in the ring, one of which is an O atom.