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Investigation of two‐ and three‐bond carbon–hydrogen coupling constants in cinnamic acid based compounds
Author(s) -
Pierens Gregory K.,
Venkatachalam Taracad K.,
Reutens David C.
Publication year - 2016
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.4469
Subject(s) - chemistry , coupling constant , density functional theory , hydrogen bond , computational chemistry , cinnamic acid , coupling (piping) , j coupling , molecule , proton , stereochemistry , nuclear magnetic resonance spectroscopy , organic chemistry , quantum mechanics , physics , mechanical engineering , engineering
Two‐ and three‐bond coupling constants ( 2 J HC and 3 J HC ) were determined for a series of 12 substituted cinnamic acids using a selective 2D inphase/antiphase (IPAP)‐single quantum multiple bond correlation (HSQMBC) and 1D proton coupled 13 C NMR experiments. The coupling constants from two methods were compared and found to give very similar values. The results showed coupling constant values ranging from 1.7 to 9.7 Hz and 1.0 to 9.6 Hz for the IPAP‐HSQMBC and the direct 13 C NMR experiments, respectively. The experimental values of the coupling constants were compared with discrete density functional theory (DFT) calculated values and were found to be in good agreement for the 3 J HC . However, the DFT method under estimated the 2 J HC coupling constants. Knowing the limitations of the measurement and calculation of these multibond coupling constants will add confidence to the assignment of conformation or stereochemical aspects of complex molecules like natural products. Copyright © 2016 John Wiley & Sons, Ltd.