Karplus Equation

Wikipedia Article
Gives the coupling constant between two Vicinal hydrogens

$J(\varphi )=C\cos (2\varphi )+B\cos (\varphi )+A$

• $J$ is the coupling constant
• $\varphi$ is the angle between two vicinal hydrogens when looking collinearly along the $\mathrm{C}-\mathrm{C}$ bond

Graph