title: 1H, 13C and 19F NMR spectroscopy of polyfluorinated ureas. Correlations involving NMR chemical shifts and electronic substituent effects.
abstract: Seventeen N-(mono-, di-, tri-, tetra- and penta-fluorophenyl)-N'-(3-nitrophenyl)ureas were prepared and characterized. Complete assignment of their (1)H, (13)C and (19)F NMR data was undertaken and the correlation of the chemical shifts of the ureido protons with field-inductive and mesomeric electronic substituent parameters was studied using the Swain-Lupton model. The best correlations were obtained when the study was limited to certain substitution patterns, e.g. non-ortho, mono-ortho- and di-ortho-fluorinated ureas, which reveal probable changes in conformations caused by the degree of ortho fluorination at the phenyl ring. Additionally, there is an excellent linear cross-correlation between the chemical shifts of the fluorine atoms and the ipso carbon atoms for the whole group of fluorinated ureas.
authors.affiliation: Departamento de Química Orgánica, Universitat de Valencia, Dr. Moliner 50, 46100 Burjassot (Valencia), Spain. antonio.abad@uv.es
authors.forename: Antonio
authors.initials: A
authors.lastname: Abad
authors.forename: Consuelo
authors.initials: C
authors.lastname: Agulló
authors.forename: Ana C
authors.initials: AC
authors.lastname: Cuñat
authors.forename: Cristina
authors.initials: C
authors.lastname: Vilanova
mesh_terms: D002247:Carbon Isotopes / Q000737:chemistry*; D004583:Electrons; D017611:Fluorine Compounds / Q000737:chemistry*; D005462:Fluorine Radioisotopes / Q000737:chemistry*; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011108:Polymers / Q000737:chemistry; D011522:Protons; D014508:Urea / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D017611:Fluorine Compounds; D005462:Fluorine Radioisotopes; D011108:Polymers; D011522:Protons; D014508:Urea