1H chemical shifts in NMR. Part 21--prediction of the 1H chemical shifts of molecules containing the ester group: a modelling and ab initio investigation

Magnetic Resonance in Chemistry : MRC
Raymond J AbrahamRichard J Smith

Abstract

The 1H NMR spectra of 24 compounds containing the ester group are given and assigned. These data were used to investigate the effect of the ester group on the 1H chemical shifts in these molecules. These effects were analysed using the CHARGE model, which incorporates the electric field, magnetic anisotropy and steric effects of the functional group for long-range protons together with functions for the calculation of the two- and three-bond effects. The effect of the ester electric field was given by considering the partial atomic charges on the three atoms of the ester group. The anisotropy of the carbonyl group was reproduced with an asymmetric magnetic anisotropy acting at the midpoint of the carbonyl bond with values of Deltachi(parl) and Deltachi(perp) of 10.1 x 10(-30) and -17.1 x 10(-30) cm3 molecule(-1). An aromatic ring current (=0.3 times the benzene ring current) was found to be necessary for pyrone but none for maleic anhydride. This result was confirmed by GIAO calculations. The observed 1H chemical shifts in the above compounds were compared with those calculated by CHARGE and the ab initio GIAO method (B3LYP/6-31G**). For the 24 compounds investigated with 150 1H chemical shifts spanning a range of ca 10 ppm, th...Continue Reading

References

Sep 1, 1988·Journal of Medicinal Chemistry·A E Howard, P A Kollman
May 24, 2003·Journal of Magnetic Resonance·Martin J PackerChristopher A Hunter

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Citations

Sep 7, 2013·The Journal of Organic Chemistry·José G NapolitanoGuido F Pauli
Jun 30, 2015·The Journal of Organic Chemistry·Graeme BarkerAi-Lan Lee
Jul 21, 2007·Magnetic Resonance in Chemistry : MRC·Ernani A BassoRaymond J Abraham
Apr 20, 2017·Magnetic Resonance in Chemistry : MRC·Raymond J Abraham, M Ashley Cooper
Apr 7, 2007·The Journal of Physical Chemistry. B·Santiago AparicioJosé M Leal

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