Pyrrolidine, also known as tetrahydropyrrole, is a saturated five-membered heterocyclic ring, which is miscible with water. Pyrrolidine exists in many alkaloids and drug molecules, such as kappa opioids, antagonists of dopamine D4 receptors, and HIV reverse transcriptase inhibitors.
Fluorene is a polycyclic aromatic hydrocarbon insoluble in water and soluble in many organic solvents. Fluorenes are one of the most important fluorescent molecules with applications in polymers, electronic devices, sensors, and photochromic materials.