Fluorine physical constants

Summary.—The gradation in characters which the halogens show with increasing at. wt. from fluorine to iodine, yields one of the most typical family series of elements. The best representative values of some of the physical constants of the halogens are summarized in Table II. The family relationship of the halogens... 

Physical constants of several partially fluorinated biphenyls (up to the 2,2, 3,4, -5,5, 6-heptafluoro-compound), obtained by a range of classical methods including the Friedel-Crafts, Ullmann, and Balz-Schiemann reactions, have been reported, and 1,8-difluoro- or 1,4,5-trifluoronaphthalene may be obtained by conventional routes (nitration, reduction, diazotization) from 1,8-diamino- or 1,5-difluoro-naphthalene, respectively. ... 

Curiously, fluorine incorporation can result in property shifts to opposite ends of a performance spectrum. Certainly with reactivity, fluorine compounds occupy two extreme positions, and this is true of some physical properties of fluoropolymers as well. One example depends on the combination of the low electronic polarizability and high dipole moment of the carbon-fluorine bond. At one extreme, some fluoropolymers have the lowest dielectric constants known. At the other, closely related materials are highly capacitive and even piezoelectric. 

Although Parylene-N possesses an outstanding combination of physical, electrical, and chemical properties, the benzylic C—H bonds present are potential sites for thermal and oxidative degradation. It is well known that replacing a C— bond with a C—F bond not only enhances the thermal stability of the resulting polymer, but also reduces the dielectric constant. Because incorporation of fluorine is known to impart thermal and oxidative stability, it became of interest to prepare poly(a,a,a, a -tetrafluoro- p -xylylene), Parylene-F Joesten reported that the decomposition temperature of poly(tetrafluoro-j9-xylylene) is ca. 530°C. Thus, it seemed that the fluorinated analog would satisfy many of the exacting requirements for utility as an on-chip dielectric medium. 

Highly fluorinated molecules have a nonpolar character and an extremely low polarizability, inducing only weak intra- and intermolecular interactions. As a consequence, perfluorocarbons behave almost like ideal liquids they are very compressible and have very high vapor pressure. For example, the physical properties of perfluoro-hexane, heptafluorohexane, and hexane are reported in Table 1.2 The effect of the polar character of the hemifluorinated compound (heptafluorohexane) on the dielectric constant value is remarkable. 

Chemical nature and concentrations of the constituants In a first step, the physical parameters were kept constant (180°C, 24 h, autogenous pressure). Different studies proved first that if NH4F is used instead of HF as a source of F, only one structure type, called CJ2 or NH4A1P04(OH)o.3Fo.7, appears whatever the nature of the amine in the system. Attempts with other alkaline fluorides provide open framworks without incorporated fluorine [29], This explains that HF was used in the following. 

Kaslin, V.M. 1983b. Tables of Force Constants ke Vibration Constants coe of Ground Electronic States of Diatomic Molecules, Composed of Atoms with Composition of s and p Shells (Atom from Chemical Groups of Nitrogen, Oxygen, Fluorine, and Neon). Preprint 303. Moscow Optics Laboratory, Optics and Spectroscopy Department, Physical Institute. 

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