Two‐Dimensional NMR Studies of Polyene Systems. I. All‐trans‐Retinal

Two‐dimensional (2‐D) NMR results are presented for all‐trans‐retinal. 2‐D J‐resolved 1H‐NMR separated the multiplets of the olefinic protons and accurately determined their chemical shifts. 2‐D shift‐correlated 1H‐NMR gave the connectivities between scalar coupled protons. From the observed H,H long‐range couplings the assignment of the methyl resonances was possible. 2‐D J‐resolved 13C‐NMR separated overlapping C,H‐multiplets and allowed analysis of the C,H long‐range couplings, 2‐D shift‐correlated 13C‐NMR related each directly bonded C,H‐pair in this molecule. The potential of 2‐D NMR in resolving and identifying individual resonances in polyene spectra is discussed.