Fluorine positions

Fluorinated Position (Compound) A Er (kcal/mol) Gas Phase (Aqueous Phase) qFb (AqF)b GIAO-NMR S,9F (A8,9F) (PPm) C-F Bond Length (Angstroms)... 

Regarding other fluorine positions on the phenyl ring it is observed that ortho-fLuorine atoms give the largest and most sensitive values some reported values<1966,19) are shown in Table XXIII. For the purposes of comparison the data of Nichols<1969,121) shown in Table XXIV is of interest. 

The reactivity depends on the nature of the substituent in the 4-position,1415 with S02NH2 > S03NH4 > H, and also on the fluorine position, as 4-fluoro-2,1,3-bcnzoxadiazole is susceptible to fluoride elimination by sodium methanethiolate, in contrast to 5-fluoro-2,1,3-benzoxadi-azole.16... 

Since F + cannot be eliminated, electrophilic ipso attack at a fluorinated position and subsequent replacement of fluorine by, for example. N-substituents is not possible. Under these conditions, addition of the electrophile or oxidation to quinoid structures is observed.202... 

A convenient method for defining helical symmetry and calculating the distribution of Intensity In a fiber pattern was devised by Cochran, Crick and Vand (CCV) (4). As Indicated in Figure 1, the molecular conformation is treated as a regular series of diffraction units uniformly spaced along a helix of pitch, P, with axial separation, s. In PTFE, one helix defines the carbon positions two helices define fluorine positions. If there is a meaningful translational Identity, c, It follows that P/s will be the ratio of small whole numbers ... 

The last two elements either occupy lk, Vi, V-t, 3/4,3/4,3/4 F.C. separately or are statistically distributed over these positions. The metal atoms are statistically distributed over the calcium positions of Cal 2. The nitrogen atom takes the place of the calcium atom in CaF2, and the two kinds of metal atoms are statistically distributed over the fluorine positions. 

No one has commercialized the fluorine positive electrode, possibly the most powerful oxidant (cathode) known, though there has been considerable effort. 

Fig. 10. The H-bonding environment (stereoview) about the AsF6" anion, derived from the low-temperature (125 K) X-ray crystal structure of (TMTSF)2AsF6, is far more symmetrical than that of the C104 anion (39). For clarity the AsF6 anion has been drawn in an ordered configuration with the fluorine atoms occupying six positions. A disordered model with 12 partially occupied fluorine positions gives similar results.

Crystals of Xe(OSeFs)2 are rhombohedral, space group R3m. At 23.5 C the hexagonal axes are fl - 6 = 8.588 (3) and c - 11.918 (3) A Z = 3, da cd = 3.345 g cm"3, and V = 761.23 AL The molecule lies on a threefold axis, and there is orientational disorder of the oxygen and fluorine positions. X-ray diffraction data obtained with an automatic diffractometer were analyzed on the basis of a molecular model with some constraints based on chemical considerations to reduce the number of independent parameters of the poorly resolved oxygen and fluorine atoms. For 122 unique reflections with > a(F ) and with anisotropic thermal parameters, R = 0.064. Bond distances are Xe-0 2.12 (5), Se-0 1.53 (5), and Se-F = 1.70 (2) A (uncorrected) and Se-F = 1.77 A (corrected for thermal motion). 

Cpd. No. Fluorine position Stereochemistry % Increase in Seizvu-e Threshold... 

Small substituents were needed in the fluorine position. 

Fig. 7b. The heterogeneous Bauverb nde" [" Y + Dxl and [ Y(31) + D Yj ], constructed by adding Dx twice. The first Bauverband" describes tfie fluorine positions in Cs6e2Fg, the second the / Mn structure. [T" - Y ] represents the fluorine position in (Sn2F3)Cl. In [ Y(31) + D Y ] the 12 neighbors of a D Yjf point [J] and the 12 + 2 neighbors of a Y (31) point are shown...

The first eight residual electron density maxima as found in ti-03.res are very close to the fluorine positions (see Figure 5.13). Together with the relatively high U values of the F-atoms, this result indicates that the fluorine atoms are also disordered. Therefore we delete all current F-atoms and replace them with the new sites taken from the Q-positions. To make sure that all new F-atoms belong to the right component, one should check the Al-F distances (or Al-Q distances, respectively), which are supposed to be about 1.7 A. This is much easier after generating the symmetry equivalent atoms. 

Fig. 5.13 Residual electron density maxima next to the fluorine positions indicating the F atoms to be part of the disorder.

Compound (Fluorine Positions) C-C Bond Length C-F Bond Length ... 

The addition of F has also been studied with ethylenes ( ). In intramolecular competition with fluorohydroolefins, the F atoms react preferentially with less fluorinated positions. Inter-... 

Also in [SbF Cle-J" compounds, some V( Sb- F) values have been observed (Figure 3) the typical range is 1859-2088 Hz and, as with arsenic, the values depend on the fluorine position around the antimony atom. 

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