🇺🇦 nmr_spectroscopy / organic chemistry ⌬

In today’s #NMRMultiplet we’re going to consider this complex 1H NMR signal from a norbornane derivative (centered at 2.23 ppm, labeled (tdd). 🔍 Feature Highlights: 1️⃣ Distinct W-Coupling (4J): Highlighted with the red curved line in the picture is a clear 4J(H,H) W-coupling (approximately 3.5 Hz) to a bridge syn-proton. The unique rigid skeleton provides the ideal geometry for this strong long-range “W” interaction. 2️⃣ Negligible Bridgehead Coupling (3J): Notice that there is no 3J coupling to the adjacent bridgehead proton. This is a classic Karplus relationship in action: the dihedral angle between this target proton and the bridgehead H is approximately 90°, predicting a vicinal constant near zero. 3️⃣ Decoding the rest: The other three couplings in our splitting tree are: 14.67 Hz, 14.67 Hz, and 11.13 Hz. They come from vicinal 3J(H,F) interactions and a geminal 2J(H,H) pairing. #coupling #norbornane