Место издания:The Magnetic Resonance Spectroscopy Division of the Gesellschaft Deutscher Chemiker (GDCh) Frankfurt
Первая страница:277
Последняя страница:277
Аннотация:Natural (-)-menthol is widely-used in NMR spectroscopy as a standard reference compound for testing new experiments due to relatively simple almost first-order 1H NMR spectrum. Most of those studies were devoted to assignment of 1H and 13C NMR signals (see e.g. [1-2]). However, exact values of 1H-1H spin-spin couplings are not documented in the literature yet. For this reason, here we report results of lineshape analysis of high resolution 1H NMR multiplets in menthol, which provides accurate values of these couplings. Relative signs of couplings were experimentally determined by COSY-45 and multiplet-selective 2D-COSY with soft-pulse excitation [3]. Simultaneously we performed FPT DFT (B3LYP/6-311++G(d,p)) calculations of spin-spin coupling constants for all reasonable conformers of menthol. Comparison of experimental and calculated couplings allowed us to establish the preferable orientation of the two substituents (isopropyl and hydroxyl) to cyclohexane moiety.