Evaluation of 13C NMR spectra of cyclopropenyl and cyclopropyl acetylenes by theoretical calculations

Abstract

A convenient methodology was developed for a very accurate calculation of 13 C NMR chemical shifts of the title compounds. GIAO calculations with density functional methods (B3LYP, B3PW91, PBE1PBE) and 6-311+G(2d,p) basis set predict experimental chemical shifts of 3-ethynylcyclopropene (1), 1-ethynylcyclopropane (2) and 1,1-diethynylcyclopropane (3) with high accuracy of 1{2 ppm. The present article describes in detail the e¬ect of geometry choice, density functional method, basis set and e¬ect of solvent on the accuracy of GIAO calculations of 13 C NMR chemical shifts. In addition, the particular dependencies of 13 C chemical shifts on the geometry of cyclopropane ring were investigated.

GIAO Calculations of Chemical Shifts in Ethene‐1,1,2,2‐tetrayltetramethylene tetrathiocyanate

“…As well as being very economical with respect to computational resources, density functional calculations would be more suitable for studying typical chemical molecules, especially taking into account that large basis sets are required for NMR properties prediction. [26] To test the different theoretical approaches (HF, DFT/ B3LYP) reported here, computed and experimental [16] 1 H and 13 C chemical shifts in the DMSO-d 6 solution and in the solid state of ethene-1,1,2,2-tetrayltetramethylene tetrathiocyanate were compared. More commonly, however, the NMR spectrum is used in conjunction with other forms of spectroscopy and chemical analysis to determine the structures of complicated organic molecules.…”