Final answer:
Molecules that have a change in dipole moment during vibration such as CO₂, OCS, H₂O, and CH₂CH₂ interact with infrared radiation and will show infrared absorption, while N₂, O₂, and H₂, which lack a change in dipole moment, will not.
Step-by-step explanation:
In the context of infrared spectroscopy, not all molecules will have transitions in an infrared spectrum. Molecules must have a change in dipole moment during vibration to interact with infrared radiation and exhibit infrared absorption. Homonuclear diatomic molecules like N₂ and O₂ do not have a permanent dipole moment and do not develop one during vibrational motion, so they will not show infrared absorption.
However, molecules such as CO₂, OCS, H₂O, and CH₂CH₂ have polar bonds or asymmetrical shapes leading to a change in dipole moment as they vibrate, so these will show absorption in the infrared spectrum. The mentioned H₂ does not have a dipole moment and will not show a transition. Lastly, C₆H is not well-defined as molecules are typically represented with both the number of carbon and hydrogen atoms specified, so it's unclear if this has a transition without further clarification on the molecular structure.