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Title: Distinguishing tautomerism in the crystal structure of (Z)-N-(5-ethyl-2,3-di-hydro-1,3,4-thiadiazol-2-ylidene) -4-methylbenzenesulfonamide using DFT-D calculations and {sup 13}C solid-state NMR

The crystal structure of (Z)-N-(5-ethyl-2,3-di-hydro-1,3,4-thiadiazol-2-ylidene) -4-methylbenzenesulfonamide contains an imine tautomer, rather than the previously reported amine tautomer. The tautomers can be distinguished using dispersion-corrected density functional theory calculations and by comparison of calculated and measured {sup 13}C solid-state NMR spectra. The crystal structure of the title compound, C{sub 11}H{sub 13}N{sub 3}O{sub 2}S{sub 2}, has been determined previously on the basis of refinement against laboratory powder X-ray diffraction (PXRD) data, supported by comparison of measured and calculated {sup 13}C solid-state NMR spectra [Hangan et al. (2010 ▶). Acta Cryst. B66, 615–621]. The mol@@ecule is tautomeric, and was reported as an amine tautomer [systematic name: N-(5-ethyl-1,3,4-thia@@diazol-2-yl)-p-toluene@@sulfonamide], rather than the correct imine tautomer. The protonation site on the mol@@ecule’s 1,3,4-thia@@diazole ring is indicated by the inter@@molecular contacts in the crystal structure: N—H⋯O hydrogen bonds are established at the correct site, while the alternative protonation site does not establish any notable inter molecular inter@@actions. The two tautomers provide essentially identical Rietveld fits to laboratory PXRD data, and therefore they cannot be directly distinguished in this way. However, the correct tautomer can be distinguished from the incorrect one by previously reported qu@@anti@@tative criteria based on the extent of structural distortion on optimization of the crystalmore » structure using dispersion-corrected density functional theory (DFT-D) calculations. Calculation of the {sup 13}C SS-NMR spectrum based on the correct imine tautomer also provides considerably better agreement with the measured {sup 13}C SS-NMR spectrum.« less
Authors:
; ; ;  [1]
  1. Department of Pharmacy, University of Copenhagen, Universitetsparken 2, Copenhagen DK-2100 (Denmark)
Publication Date:
OSTI Identifier:
22351162
Resource Type:
Journal Article
Resource Relation:
Journal Name: Acta crystallographica. Section C, Structural chemistry (Online); Journal Volume: 70; Journal Issue: Pt 8; Other Information: PMCID: PMC4174016; PMID: 25093360; PUBLISHER-ID: fa3347; OAI: oai:pubmedcentral.nih.gov:4174016; Copyright (c) Li et al. 2014; This is an open-access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United Kingdom
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BENZENE; CRYSTAL STRUCTURE; DENSITY; DISPERSIONS; HYDROGEN; ISOMERIZATION; NMR SPECTRA; NUCLEAR MAGNETIC RESONANCE; OPTIMIZATION; POWDERS; RINGS; SOLIDS; TOLUENE; X-RAY DIFFRACTION