Carbon-13 NMR spectroscopy

Need to know

What you need to know

• Only the ¹³C isotope is NMR-active.
• The low natural abundance (1.1%) of ¹³C means the technique is less sensitive than ¹H NMR.
• The chemical environment (shielding/deshielding) determines the exact radio frequency absorbed.
• The probability of two ¹³C atoms being adjacent is very low, so ¹³C-¹³C coupling is ignored.

Explanation

Carbon's Chemical Fingerprint

1. Each distinct C environment gives one peak. | Sim hint: Symmetry reduces peak count.
2. Chemical shift δ in ppm from TMS. | Sim hint: C=O ~ 160–220 ppm.
3. No C–H splitting in ¹³C NMR (decoupled). | Sim hint: Simpler than proton NMR.
4. Count peaks → deduce carbon environments. | Sim hint: Match to proposed structure.