685-64-3Relevant academic research and scientific papers
Catalytic defluorination of perfluorinated aromatics under oxidative conditions using N-bridged diiron phthalocyanine
Colomban, Cédric,Kudrik, Evgenij V.,Afanasiev, Pavel,Sorokin, Alexander B.
supporting information, p. 11321 - 11330 (2014/11/07)
Carbon-fluorine bonds are the strongest single bonds in organic chemistry, making activation and cleavage usually associated with organometallic and reductive approaches particularly difficult. We describe here an efficient defluorination of poly- and perfluorinated aromatics under oxidative conditions catalyzed by the μ-nitrido diiron phthalocyanine complex [(Pc)Fe III(μ-N)FeIV(Pc)] under mild conditions (hydrogen peroxide as the oxidant, near-ambient temperatures). The reaction proceeds via the formation of a high-valent diiron phthalocyanine radical cation complex with fluoride axial ligands, [(Pc)(F)FeIV(μ-N)FeIV(F) (Pc+?)], which was isolated and characterized by UV-vis, EPR, 19F NMR, Fe K-edge EXAFS, XANES, and Kβ X-ray emission spectroscopy, ESI-MS, and electrochemical techniques. A wide range of per- and polyfluorinated aromatics (21 examples), including C6F6, C6F5CF3, C6F5CN, and C6F5NO2, were defluorinated with high conversions and high turnover numbers. [(Pc)FeIII(μ-N)Fe IV(Pc)] immobilized on a carbon support showed increased catalytic activity in heterogeneous defluorination in water, providing up to 4825 C-F cleavages per catalyst molecule. The μ-nitrido diiron structure is essential for the oxidative defluorination. Intramolecular competitive reactions using C6F3Cl3 and C6F3H 3 probes indicated preferential transformation of C-F bonds with respect to C-Cl and C-H bonds. On the basis of the available data, mechanistic issues of this unusual reactivity are discussed and a tentative mechanism of defluorination under oxidative conditions is proposed.
Hydrogen-bond symmetry in difluoromaleate monoanion
Perrin, Charles L.,Karri, Phaneendrasai,Moore, Curtis,Rheingold, Arnold L.
supporting information; experimental part, p. 7766 - 7772 (2012/07/02)
The symmetry of the hydrogen bond in hydrogen difluoromaleate monoanion is probed by X-ray crystallography and by the NMR method of isotopic perturbation in water, in two aprotic organic solvents, and in an isotropic liquid crystal. The X-ray crystal structure of potassium hydrogen difluoromaleate shows a remarkably short O-O distance of 2.41 A and equal O-H distances of 1.206 A, consistent with a strong and symmetric hydrogen bond. Incorporation of 18O into one carboxyl group allows investigation of the symmetry of the H-bond in solution by the method of isotopic perturbation. The 19F NMR spectra of the mono-18O-substituted monoanion in water, CD2Cl2, and CD3CN show an AB spin system, corresponding to fluorines in different environments. The difference is attributed to the perturbation of the acidity of a carboxylic acid by 18O, not to the mere presence of the 18O, because the mono-18O dianion shows equivalent fluorines. Therefore, it is concluded that the monoanion exists as an equilibrating pair of interconverting tautomers and not as a single symmetric structure not only in water but also in organic solvents. However, in the isotropic liquid crystal phase of 4-cyanophenyl 4-heptylbenzoate, tetrabutylammonium hydrogen difluoromaleate- 18O shows equivalent fluorines, consistent with a single symmetric structure. These results support earlier studies, which suggested that the symmetry of hydrogen bonds can be determined by the local environment.
Molecular structure of 3,4-difluorofuran-2,5-dione (difluoromaleic anhydride) as determined by electron diffraction and microwave spectroscopy in the gas phase and by theoretical computations
Abdo, Basil T.
, p. 1758 - 1767 (2007/10/03)
The structure of 3,4-difluorofuran-2,5-dione has been determined experimentally in the gas phase by microwave spectroscopy using rotation constants derived from five isotopomers and by a combined analysis of electrondiffraction and microwave data. The geometry is planar with C2v symmetry. Structural parameters [distances (rαo)/pm, angles a/deg, (1α errors)] for the combined analysis are: r(C=O) = 119.0(1); r(C-F) = 130.9(2); r(C=C) = 133.2(3); r(O-C) = 139.3(1); KC-C) = 148.5(2); C-C=C = 108.3(1); ZC=C-F = 129.9-(1); C-C=O = 129.3(1); C-O-C = 108.9(1); O-C-C = 107.2(1). These values are in excellent agreement with those obtained in an ab initio study of the molecular geometry at the MP2/6-311+G (2df) level of theory. The dipole moment of difluoromaleic anhydride has been determined experimentally by Starkeffect measurements to be 1.867(3) D.
ELIMINATION OF HYDROGEN FLUORIDE FROM FLUORINATED SUCCINIC ACIDS.(II) KINETICS OF DEHYDROFLUORINATION OF FLUORO-, 2,2-DIFLUORO-, MESO- AND DL-2,3-DIFLUORO-, AND TRIFLUOROSUCCINIC ACIDS
Hudlicky, M.,Glass, T. E.
, p. 15 - 28 (2007/10/02)
Elimination of hydrogen fluoride from fluorosuccinic acid gave fumaric acid, from 2,2-difluorosuccinic acid, meso- and DL-2,3-difluorosuccinic acid fluorofumaric acid, and dehydrofluorination of trifluorosuccinic acid afforded difluoromaleic acid.Kinetic data based on 1H NMR measurements are presented for temperatures of 60 deg C, 75 deg C and 90 deg C.All the dehydrofluorinations follow second order kinetics.Activation energies for the dehydrofluorination of the above acids were found to be: 19.3, 17.3, 18.8, 17.9 and 18.3 kcal, respectively.Since both diastereomeric 2,3-difluorosuccinic acids give fluorofumaric acid as the only product of dehydrofluorination, one of them (DL) undergoes trans elimination while the other (meso) must undergo cis elimination.
