How Infrared Spectroscopy Works
Think of covalent bonds as tiny springs that are constantly vibrating. When you shine infrared light through a compound, these bonds absorb energy at specific frequencies and vibrate even more. It's a bit like how different guitar strings vibrate at different pitches.
The vibration frequency depends on three key factors: how heavy the atoms are, how strong the bond is, and what type of vibration occurs. Stronger bonds vibrate faster (higher frequency), whilst heavier atoms make bonds vibrate more slowly (lower frequency).
There are three main types of bond vibrations you need to know: symmetric stretch (both ends moving outward together), asymmetric stretch (one end moving out whilst the other moves in), and bending (the bond angle changing).
Quick Tip: Remember that stronger = faster vibrations, heavier atoms = slower vibrations.
Scientists measure these vibrations using wavenumbers (cm⁻¹) on the x-axis, which is proportional to frequency. Most useful IR absorption happens between 4,000-400 cm⁻¹.
