J

J-coupling

Quick Reference
Also Known AsScalar coupling, spin-spin coupling, NMR coupling constant, vicinal coupling

What is J-coupling?

J-coupling (scalar coupling or spin-spin coupling) is the interaction between nuclear spins in NMR spectroscopy that is transmitted through chemical bonds. It causes splitting of NMR peaks into multiplets. The coupling constant J (measured in Hz) provides information about the number and type of neighboring atoms. J-coupling follows the n+1 rule: n equivalent neighboring protons split a signal into n+1 lines.

Properties & Characteristics

Units: Hz (hertz). Transmitted through bonds: vicinal ³J typically 0–20 Hz; geminal ²J typically 0–30 Hz. Karplus equation: ³J_HH = A cos²θ + B cosθ + C (dihedral angle dependence). ³J = 0–8 Hz (coupling with O, N between them). Long-range coupling: ⁴J, ⁵J = 0–5 Hz. Equivalent protons: no splitting observed.

Uses & Applications

NMR structure determination of organic molecules. Determining dihedral angles and conformation. Identifying number of neighboring H atoms (n+1 rule). Confirming connectivity in organic molecules. Pharmaceutical structure elucidation. Protein structure determination by NMR. Measuring molecular dynamics.

Safety Information

NMR spectrometers use strong magnetic fields — pacemakers/implants hazard. High-field instruments (>600 MHz) require oxygen monitoring (liquid He/N₂ quench risk). No chemical safety concern from J-coupling itself.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term J-coupling
Synonyms Scalar coupling, spin-spin coupling, NMR coupling constant, vicinal coupling

Frequently Asked Questions

J-coupling (scalar coupling or spin-spin coupling) is the interaction between nuclear spins in NMR spectroscopy that is transmitted through chemical bonds. It causes splitting of NMR peaks into multiplets. The coupling constant J (measured in Hz) provides information about the number and type of neighboring atoms. J-coupling follows the n+1 rule: n equivalent neighboring protons split a signal into n+1 lines.

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