Azulenes

**Definition:** Compounds based on a seven-membered ring fused to a five-membered ring. Heat can rearrange them to NAPHTHALENES which have two fused six-membered rings. They are similar to guaiazulenes which are SESQUITERPENES with a six-membered ring fused to a five-membered ring.

**Tree numbers:** - D02.455.426.392.368.284.049 - D02.455.426.559.847.133 - D04.615.133