Fluorine dimer

Dynamic correlation, at the MP2 level of theory, is very important for the prediction of accurate energetics for these species. While MP2 was not very important for the prediction of geometries for the fluorine dimer, it was essential for the geometry predictions for the heavier congeners. The effective core potential basis set overestimates the dimerization energy of TiF4 by about 4 kcal/mol, but it was quite reliable for the heavier species. 

Hosono, H., Mizuguchi, M., Kawazoe, H., and Ogawa, T., Effects of fluorine dimer excimer laser radiation on the optical transmission and defect formation of various types of synthetic SiOj glasses, Appl. Phys. Lett. 74, 2755 (1999). 

Scheme 20 Synthesis of fluorinated dimeric phthalocyanine and Pc-peptide conjugate...

Fig. 9 Molecular structure of syn- and onti-topoisomers of the fluorinated dimer 183 (CCDC 181315,181316) [100]...

Fig. 1 A cartoon representation of volume element of the electron density at the bond critical point (bcp) and associated tensile and compressive modes of the stress tensor in ethane and the fluorine dimer. The rectangular prism represents the volume element at the bcp it is deformed in a way that reveals the relative importance of tensile (stretching) and compressive (squeezing) forces on the bond...

Weber T A and Stillinger F FI 1990 Dynamioal branohing during fluorination of the dimerized Si (100) surfaoe a moleoular dynamios study J. Chem Phys. 92 6239-45... 

The fluorinated titanocycle related to (28) is not obtained from C H CMUCgF. Photolysis of CP2T1X2 always gives first scission of a Cp—Tibond. In a chlorinated solvent, the place vacated by Cp is assumed by Cl. In the absence of some donor, the radical dimerizes (298—299). 

Bismuth Penta.fIuoride, Bismuth(V) fluoride consists of long white needles that have been shown to have the same stmcture as the body-centered, tetragonal a-polymorph of uranium hexafluoride. The density of the soHd is 5.4 g/mL at 25°C. The soHd consists of infinite chains of trans-bridged BiF polyhedra dimers and trimers are present in the vapor phase (22). Bismuth pentafluoride may be prepared by the fluorination of BiF or... 

In dimers composed of equal molecules the dimer components can replace each other through tunneling. This effect has been discovered by Dyke et al. [1972] as interconversion splitting of rotational levels of (HF)2 in molecular beam electric resonance spectra. This dimer has been studied in many papers by microwave and far infrared tunable difference-frequency laser spectroscopy (see review papers by Truhlar [1990] and by Quack and Suhm [1991]). The dimer consists of two inequivalent HE molecules, the H atom of one of them participating in the hydrogen bond between the fluorine atoms (fig. 60). PES is a function of six variables indicated in this figure. 

Isocyanides react with fluorine [75 to yield difluoromethylene imines, which tend to dimerize In an inert solvent, imines accept fluorine fioin trifluoromethyl hypofluorite [76, 77] (equation 11)... 

The behavior of strained,/Zuorimiret/ methylenecyelopropanes depends upon the position and level of fluorination [34], l-(Difluoromethylene)cyclopropane is much like tetrafluoroethylene in its preference for [2+2] cycloaddition (equation 37), but Its 2,2-difluoro isomer favors [4+2] cycloadditions (equation 38). Perfluoromethylenecyclopropane is an exceptionally reactive dienophile but does not undergo [2+2] cycloadditions, possibly because of stenc reasons [34, 45] Cycloadditions involving most possible combinations of simple fluoroalkenes and alkenes or alkynes have been tried [85], but kinetic activation enthalpies (A/f j for only the dimerizations of tetrafluoroethylene (22 6-23 5 kcal/mol), chlorotri-fluoroethylene (23 6 kcal/mol), and perfluoropropene (31.6 kcal/mol) and the cycloaddition between chlorotnfluoroethylene and perfluoropropene (25.5 kcal/mol) have been determined accurately [97, 98] Some cycloadditions involving more functionalized alkenes are listed in Table 5 [99. 100, 101, 102, 103]... 

Excimer lasers use gases, but because of their special properties are usually considered as a class of their own. Excimer is short for excited dimer, which consists of two elements, such as argon and fluorine, that can be chemically combined in an excited state only. These lasers typically emit radiation with veiy small wavelengths, in the ultraviolet region of the electromagnetic spectrum. This shorter wavelength is an enormous advantage for many applications. 

M - 2 Aromatic isocyanates Aromatic phenols Certain butenols Certain fluorinated amines e.g., C8F17CH2CHICH2NH2 or CF3(CF2)7CH2CH2CH2NH2 Possible Precursor Compounds Polynuclear aromatics (e.g., dihydroxyphenanthrene) Ethylsilanes (dimers to heptamers)... 

Despite the body of evidence in favor of the Mayo mechanism, the formation of diphenylcyclobutanes (90, 91) must still be accounted for. It is possible that they arise via the 1,4-diradical 94 and it is also conceivable that this diradical is an intermediate in the formation of the Diels-Alder adduct 95 (Scheme 3.64) and could provide a second (minor) source of initiation. Direct initiation by diradicals is suggested in the thermal polymerization of 2,3,4,5,6-pentafluorostyrene where transfer of a fluorine atom from Diels-Alder dimer to monomer seems highly unlikely (high C-F bond strength) and for derivatives which cannot form a Diels-Alder adduct. 

Carboxylic acids with a halide, hydroxy or amino group in the a-position form no dimers (Table 2, No. 11), except when two or three fluorine atoms are pr ent there (Table 2, No. 12). A large amount of work has been devoted to the coupling of fluoro-carboxylic acids (Table 2, Nos. 13-16) due to interesting properties of the produced fluorohydrocarbons. By statistical analysis optimal conditions for Kolbe ela trolysis of perfluorinated acids have been calculated [135]. 

The diradical mechanism b is most prominent in the reactions involving fluorinated alkenes. These reactions are generally not stereospecificand are insensitive to solvent effects. Further evidence that a diion is not involved is that head-to-head eoupling is found when an unsymmetrical molecule is dimerized. Thus dimerization of F2C=CFC1 gives 106, not 107. If one pair of electrons moved before the other, the positive end of one molecule would be expeeted to attack the negative end of the other. 

A model with overlapping perfluoroalkyl tail should be excluded, since in this case the difference A is independent of the length of the fluorinated chain. The calculations for the molecular form factor gives a reasonable agreement with the intensities of successive (OOn) harmonics for the model with overlapping aromatic parts of the molecules and the tilt (approximately 35°) of perfloro chains [41c]. This model also satisfies fhe requiremenfs for dense Ailing of space. The smecfic layers in fhe dimeric smecfic phase are well defined (cr = 2.5-3 A) and consisf of fwo sublayers of fhe fluorinafed and aromafic parfs of fhe molecules. 

Fig. 11a,b. Examples of one and two-dimensional structures for terminally fluorinated mesogens a antiparallel dimeric layering for the compounds with one terminal fluorinated tail (Diele et al. [38]) b two-dimensional (columnar) packing observed for the swallow-tailed fluorinated compounds solid lines indicate two-dimesional rectangular lattice (Lose et al. [41])... 

Fluorination of ClsP NMe-BCls (Section 2) by arsenic trifluoride results in the formation the well-characterized dimeric phosphazene (23) ... 

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