Carbon-13 NMR spectra of retinal1 and its related compounds

Carbon-13 NMR spectra of all-trans retinal₁ and vitamin A₁ were measured by the pulse Fourier transform method in CCl₄. All peaks in these spectra were assigned from considerations of chemical shifts, half proton-decoupled spectra, spin-lattice relaxation times and induced chemical shift by the addition of shift reagent. The carbon-13 NMR spectrum was also measured for all-trans retinal₁ which had been exposed to the sunlight for three hours, and the induced isomer was proposed to be 11-s-cis retinal₁.