Bonds to Fluorine

Bonds to Fluorine.—Some 350 lines in the microwave spectrum of NF2 have been measured between 13.0 and 65.2 Hz. A complete assignment has been achieved, and the usual molecular constants, including the average geometry, have been computed. It was confirmed that the ground-state electronic wavefunction transforms as 2Bl.173 

Using a new apparatus designed to measure very low gas solubilities (ca. 10 6mol fraction), the solubilities of NF3 (298—318 K) and N2F4 (288— 318 K) in water have been determined, and the enthalpies and entropies of solution derived.174 Shock-wave studies have been used to probe the thermal decomposition of NF3 and the reactions of NF3 and N2F4 with H2.175 

Solid NF4 salts have been prepared by a new route. When NF3, F2, and a strong fluorine acceptor (e.g. SbFs) are photolysed by u.v. light, a white solid product forms within seconds. The product is a mixture of NF4 SbFe and 02 SbFs.176 

Bonds to Fluorine.—Calculation of e.s.r. coupling constants of the ir-radicals NF2 and PF2 by the UHF method gives poor agreement with experimental data, whereas C.I. calculations yield coupling constants in good agreement with experiment.  

The geometries of a number of molecules, including NF2 and NF, have been rationalized using a hard-atom model similar to that used in describing the structures of simple ionic compounds in the solid state. The calculated F—N—F angles/ (observed angles in parentheses) are NF2 104.8 (102.5) and NF3 

6 (102.4). The results indicate that factors other than electron-pair repulsions 

NOCl is separated into Cl and NO radicals when photolysed by 3000—4000 A radiation in the vapour phase. The reaction of excited iodine atoms, produced 

The kinetics of reaction (29) have been investigated by rapid-scan i.r. spectroscopy. The experimental rate constant is in reasonable agreement with an earlier calorimetric value, but the use of isotopic NO has now established the reaction mechanism to be a Cl atom transfer. Rate constants for the nitrogen isotope exchange reactions (30) and (31) have also been determined.  

Bonds to Fluorine.—Christe and his group have reported the synthesis, and characterization by and P n.m.r. and vibrational spectroscopy, of the first known examples of NH2P2 saltsalso the application of low-temperature u.v. photolysis to the synthesis of novel (and to the improved synthesis of known) NP4 salts.The difluoroammonium salts NH2P2 SbPg and NH2P2 AsP were obtained as white crystalline solids by protonation of difluoramine in HP—MP5 (M = As or Sb) solutions according to reaction (9). They are stable at —50 °C, but 

Reactions of NOP and NO2P with PtPj, O2 PtPe, Ptp6, IrPe, NO PtP, NOj PtPfi, NO Irp6, and NOJ IrPe have been examined under a variety of conditions. The NO2 ion is found to be intrinsically unstable with respect to the elimination of oxygen in Pt and Ir fluorometallate salts. Raman spectral data for NO BPI, NO2 BFJ, NO2 Asp , NO Ptp , NOJ Ptp, (NO )2 PtPl , NO IrP, NOJ IrPe, and (NO )2 IrPe are presented and analysed.  

Vibrational excitation from a pulsed CO2 laser has been used to ignite the explosion of mixtures of N2F4 and Hg. It was concluded (a) pulsed i.r. laser radiolysis is a viable method for obtaining a fast non-equilibrium increase in the energy of a system (b) vibrational excitation results in chemical reaction more rapidly than if the same amount of energy were added thermally. 

Burden, B. T. Hart, and G. R. Williams, Theor. Chim. Acta, 

---

Hydrogen is bonded to fluorine in hydrogen fluoride by a cova... 

There are six electron pairs around the xenon atom four of these are covalent bonds to fluorine and the other two pairs are unshared. This molecule is classified as AX4E ... 

C09-0102. Using Tables 9 2 and, prepare a list of bonds to fluorine that are both longer and stronger than F—F bonds. 

Robinson, E.A., Johnson, S.A., Tang, T.-H., Gillespie, R.J. (1997). Reinterpretation of the lengths of bonds to fluorine in terms of an almost ionic model. Inorganic Chemistry, 36, 3022-3030. Schinder, H.L. Becke, A.D. (2000). Chemical contents of the kinetic energy density. Journal of Molecular Structure (THEOCHEM), 527, 51-61. 

This review is conceived as a progress report. It includes only compounds of selenium and tellurium with the element directly bonded to fluorine. The chemical literature of the last 10 years, including 1979, has been searched thoroughly, and emphasis has been placed on facts rather than on interpretation. There are some earlier reviews covering the same area "Fluorine Compounds of Selenium and Tellurium 1970 (40), "Inorganic Selenium Chemistry 1975 (48), and "Inorganic Chemistry of Tellurium 1975 (53). 

While the O—H stretching mode is a sensitive indicator of weak hydrogen bonds to fluorine and the hydrogen bond topology, there are other dynamical... 

Answer. Nitrogen undergoes sp hybridization, not sp, so it is tetrahedral. The additional sp orbital is occupied by a lone pair of electrons from the nitrogen. This lone pair results in electron-electron repulsion that causes the other sp orbitals bonded to fluorines to be closer together than the normal 109° tetrahedral bond angle, hence the 107.3 F-N-F bond angle. 

Product distribution was calculated by glc peak areas. All unmarked positions are bonds to fluorine... 

Fluorine is one of the smallest atoms, and nonpolar molecules made with fluorine atoms exhibit only very weak induced dipole—induced dipole attractions. This is the principle behind the Teflon nonstick surface. The Teflon molecule, part of which is shown in Figure 7.9, is a long chain of carbon atoms chemically bonded to fluorine atoms, and the fluorine atoms exert essentially no attractions on any material in contact with the Teflon surface—scrambled eggs in a frying pan, for instance. 

Finally, the metal-perfluoroalkyl linkage also appears to be less susceptible to facile decomposition by the a- or -elimination pathways that dominate much of the chemistry of hydrocarbon alkyls and lead to metal hydrides. The absence of these reaction pathways, at least for the later transition metals, may reflect the relative strength of the C—F bond versus the M—F bond compared to C—H/M—H analogues (32). However, a-fluoride abstraction reactions can be accomplished with exogenous fluoride acceptors to give fluorinated carbene complexes (see Section III,B,1). One example of an apparent -fluorine elimination reaction is shown in Eq. (2) (33) and presumably is driven by the stronger bond to fluorine formed by early transition... 

Hybridization. A satisfactory description of covalent bonding should also be able to account for molecular geometry, that is, for the mutual directions of bonds. Let us take for an example boron trifluoride, which is a trigonal planar molecule. Boron uses three orbitals to form three completely equivalent bonds to fluorine atoms. 

A series of strained, bridgehead fluorinated bicyclic compounds shown in Scheme 3.11 displays a large range of chemical shifts that has no obvious trend. What is surprising is the lack of correlation with s content of the orbital used by carbon to bond to fluorine, which should be decreasing along the series.4... 

Fig. 13 is a drawing of electron-domain models of some Group VI hexafluorides. Open circles represent the electron-pairs of four of the six bonds to fluorine atoms in a Lewis, single-bond formulation of these molecules. Solid circles represent the atomic cores of oxygen, sulfur, selenium, tellurium, tungsten, and uranium (core radii, in hundreths of A, 9, 29, 42, 56, 62, and 80 2>, respectively). These hexafluorides are, in order, non-existent, extra-ordinarily unreactive, hydrolyzed slowly, hydrolyzed completely at room temperature in 24 hours, hydrolyzed readily, and hydrolyzed very rapidly. 

Remember the mnemonic device, I heard about hydrogen bonding on the FON. That is, when hydrogen is bonded to fluorine, oxygen, or nitrogen, the conditions for hydrogen bonding exist. 

The reaction of the porphyrin ligand, TTP (tetra-p-tolylporphyrin) with BF3-OEt2 leads to the oxide fluoride complex, B2OF2(TTP) and the structure has been established using H, 13C, nB and 19F NMR spectroscopy and FAB mass spectrometry [9], The structure contains a B—O—B bridge in which each boron is bonded to fluorine and to a nitrogen of TTP. The structure of the diboron complex was confirmed by an X-ray crystal structure determination of the tetrakis-(p-chlorophenyl)porphyrin (TpCiPP) derivative. 

Boron forms strong bonds to fluorine (644kJmol ), usually combining with three or four fluorides in its compounds or salts. Several binary fluorides of boron are known including boron trifluoride, BF3, a stable gas of great industrial importance as a Lewis acid. Boron trifluoride is synthesized industrially by reaction of hydrofluoric acid with borates or boric oxides (equation 42). ... 

Substitution of hydrogen, in an alkene, by fluorine leads to increased reactivity for a number of processes for example, with tetrafluoroethene, heats of addition of chlorine, hydrogenation and polymerisation are 58.5, 66.9 and 71.1kJmol greater, respectively, than for the analogous reactions with ethene [3, 29]. These observations could be attributed either to an increase in the carbon-fluorine bond strength upon changing the hybridisation of the carbon atoms bonded to fluorine [30] or to ir-bond destabilisation by fluorine [31]. 

A consideration of the cyclobutene ring-opening reactions [34, 35] (Table 7.4) reveals that the changes in hybridisation of carbon bonded to fluorine are the same for both compounds T7.4A and T7.4B, and so any changes in carbon-fluorine bond energies must also be the same. Consequently, as A// for T.7.4A is more endothermic than for T7.4B,... 

---