Practice question

Splitting arises from indirect spin-spin coupling transmitted via bonding electrons, termed J-coupling or scalar coupling. Neighboring magnetic nuclei perturb energy levels through Fermi contact interaction, creating multiple transition frequencies. Equivalent neighbors split signal into n+1 components, with separation equal to coupling constant in hertz. This through-bond mechanism, not through-space, carries stereochemical information. In peptides, three-bond HN-Hα coupling reports phi angle via Karplus relationship, crucial for secondary structure determination, confirming alpha helix or beta sheet formation in proteins and elucidating metabolite connectivity patterns.