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Strong intramolecular hydrogen bonds and steric effects involving C═S groups: An NMR and computational study
Author(s) -
Elias Rita S.,
Saeed Bahjat A.,
Kamounah Fadhil S.,
Duus Fritz,
Hansen Poul Erik
Publication year - 2020
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.4959
Subject(s) - chemistry , steric effects , intramolecular force , hydrogen bond , molecule , computational chemistry , low barrier hydrogen bond , chemical shift , isopropyl , hydrogen , sextuple bond , basis set , bond length , single bond , enol , bond order , crystallography , density functional theory , group (periodic table) , stereochemistry , medicinal chemistry , organic chemistry , catalysis
A number of 5‐acyl rhodanines and thiorhodanines with bulky acyl groups (pivaloyl and adamantoyl), not previously available, have been synthesized. The compounds are shown to exist in the enol form. Structures have been calculated using both the MP2 approach and the B3LYP‐GD3BJ functional and the 6‐311++G(d,p) basis set. Hydrogen bond energies are estimated by subtracting energies of a structure with the OH group turned 180° from those of the intramolecularly hydrogen‐bonded one. Properties such as OH chemical shifts, two‐bond isotope effects on 13 C chemical shifts, electron densities at the bond critical point from atoms in molecules analysis, and the hydrogen bond energies show that the sterically hindered compounds have stronger hydrogen bonds than methyl or isopropyl derivatives. The combination of oxygen and sulfur derivatives enables a detailed analysis of hydrogen bond energies.