Unequivocal Structural Assignments of Three Cardanol - Derived: An Experimental and Theoretical Approach

Since a few decades, NMR chemical shift calculations have been used to interpret experimental spectroscopic data and to assign the structures of complex molecules.1 The combination of NMR and computational chemistry techniques has emerged as a powerful tool to determine the connectivity, conformation and stereochemistry of challenging systems.2 Theoretical methods (especially DFT) permit shielding tensors and spin-spin coupling constants to be calculated with highly reliable results.3,4 We present here a complete NMR assignment for three cardanol-derived (1, 2 and 3). These studies were performed using 1D and 2D NMR techniques and compared with the theoretical predictions of the chemical shifts using DFT calculations.Cardanol is a material obtained from cashew nut shell liquid (CNSL), which is a byproduct of cashew nut processing and represents a powerful phenolic pollutant.5,6 It can be considered as a building block for chemical synthesis and adds value to the CNSL.7 GIAO model at DFT/B3LYP theory level using cc-pVTZ basis (with and without solvent) set was employed for calculations of 1H and 13C NMR chemical shifts (δ), using Gaussian03 program.8 From correlation between the theoretical and experimental data, it was concluded that the model used was effective for calculating δ for the studied compounds. From compound 1 it was found that the mean deviation (MD), standard deviation (SD) and linear correlation factor (R) for all the calculations were generally better when using solvent. Another conclusion was that the model used was effective for calculating δ for the studied compounds