Introduction Of Fluorine Atom Research Articles

Preparation and characterization of fluorine‐containing aromatic condensation polymers. I. Preparation and characterization of fluorine‐containing polycarbonate and copolycarbonates by two‐phase phase‐transfer‐catalyzed polycondensation of 2,2‐bis (4‐hydroxyphenyl)‐1,1,1,3,3,3‐hexafluoropropane and/or 2,2‐bis (4‐hydroxyphenyl)propane with trichloromethyl chloroformate

AbstractA series of fluorine‐containing homopolycarbonate and copolycarbonates with a wide range of unit ratio were synthesized by the two‐phase phase‐transfer‐catalyzed plycondensation of 2,2‐bis (4‐hydroxyphenyl)‐1,1,1,3,3,3‐hexafluoropropane (Bisphenol AF) and/or 2,2‐bis (4‐hydroxy‐phenyl) propane (Bisphenol A) with trichloromethyl chloroformate, and the effect of the fluorine substitution on the synthesis and properties of these polymers was investigated by comparing with those of Bishphenol A‐based homopolycarbonate without fluorine. Film‐forming moderate‐to high‐molecular‐weight fluorine‐containing polycarbonates with reduced viscosities up to 0.54 dL/g were obtained in high yields by using tetra‐n‐butylammonium bromide as a catalyst, sodium hydroxide as a base, and 1,2‐dichloroethane as a medium. The reduced viscosity, however, decreased markedly with increasing feed ratio of Bisphenol AF. Their solubility in common organic solvents was clearly improved by the introduction of fluorine atom. The pliability of the films also increased remarkably with increasing fluorine content. The contact angles formed by water were larger than 90°, regardless of their fluorine contents, at 25°C in air. The critical surface tension and refractive index of Bisphenol AF‐based homopolycarbonate were ca. 20 dyn/cm and 1.426, respectively. The glass transition temperatures and thermal stability increased monotonously with increasing fluorine content.

Stabilisation of the thromboxane ring system by electron-withdrawing substituents. Mechanism and reactivity in the hydrolysis of alkyl and aryl oxetane acetals

Rates of acid-catalysed hydrolysis are reported as a function of pH for eleven oxetane acetals (6) in 20% dioxane–water. The introduction of fluorine atoms into the 2-alkoxy group results in a 103–104-fold kinetic stabilisation, and the system is also stabilised by 2-aryl substituents. The pH–rate profiles for the two most reactive compounds (3b) and (12b) show that at low pH the reaction involves rapid conversion into the intermediate hemiacetal, followed by its rate-determining decomposition. For these compounds at pH > 6, and for all other oxetane acetals studied, the ring-opening step is rate determining. No general acid catalysis is apparent.

Luminescence time parameters of fluorinated phenoxazines

The luminescent properties of fluorosubstituted phenoxazines were investigated. The emission lifetime and quantum yields of these compounds were determined. The measurements of emission lifetimes were carried out by an electro-optical chronography method using synchrotron radiation as the excitation source. The radiative and nonradiative relaxation constants were calculated. The introduction of fluorine atoms into an oxazine system leads to a reduction of the quantum yield and an increase in the nonradiative constant.

Photofragmentation dynamics of C2H5I and CF3CH2I at 248 nm

Translational photofragment spectroscopy has been used to study the photodissociation dynamics of C2H5I and CF3CH2I at 248 nm. The measured anisotropies of the photofragments show that the initial absorption is the (parallel polarized) 3 Q 0 ← N transition with a dissociation lifetime of 4 ± 2 × 10-13s in both cases. The time of flight measurements yield the energy disposal for channels leading to I (2 P 3/2) and I* (2 P 1/2) for both molecules. The average energy disposed into translation is 62 per cent (I) and 72 per cent (I*) for C2H5I, and 36 per cent (I) and 39 per cent (I*) for CF3CH2I. The quantum yield for I* production is 0·67 ± 0·03 for C2H5I and 0·82 ± 0·07 for CF3CH2I. The results, combined with those of other workers, are compared to an impulsive description of the dissociation dynamics for a variety of substituted alkyl iodides. Finally a simple Landau-Zener curve crossing model is used to highlight the substantial change in curve crossing probability caused by introduction of fluorine atoms...

A new synthetic route to 7‐halo‐1‐cyclopropyl‐6‐fluoro‐1,4‐dihydro‐4‐oxoquinoline‐3‐carboxylic acid, an intermediate for the synthesis of quinolone antibacterial agents

AbstractStarting from m‐fluorotoluene, 7‐chloro‐6‐fluoro‐ and 6,7‐difluoro‐1‐cyclopropyl‐1,4‐dihydro‐4‐oxoquino‐line‐3‐carboxylic acids, 3 and 16 were synthesized. Compounds 3 and 16 are useful intermediates for the synthesis of a class of quinolone antibacterial agents. The synthetic route involves two processes; i) construction of the quinoline ring by an intramolecular cyclization accompanied by the elimination of a nitro group and ii) introduction of fluorine atom by replacement of a nitro group with potassium fluoride. 7‐(3‐Amino‐1‐pyrroli‐dinyl)‐1‐cyclopropyl‐6‐fluoro‐1,4‐dihydro‐4‐oxoquinoline‐3‐carboxylic acid (18) was prepared from 3 or 16. The antibacterial activity of 18 compares favorably with that of ciprofloxacin (2).

Radical-anions of meta-fluorobenzonitrile derivatives

Cyclic polarometfy and ESR spectrometry were used to show that the introduction of fluorine atom into the meta position of benzonitrile leads to stabilization of the corresponding radical-anions.

Vibrational spectra of fluorine-containing azoxybenzenes

The vibrations of the azoxy group in azoxybenzene have been assigned on the basis of calculations of the frequencies and normal modes of vibrations for it. The introduction of fluorine atoms into the benzene rings has practically no influence on the frequencies of the stretching vibrations of the azoxy group. An increase in the number of fluorine atoms in the benzene rings of azoxybenzenes lowers the intensities of the stretching vibrations of the azoxy and phenyl groups in the IR spectra.

Polymers with Oligoorganosiloxane Side Chains as Material for Oxygen Permeable Membranes

Styrene and methacrylate type monomers having oligoorganosiloxane substituents were synthesized, and the properties of the polymers therefrom as material for oxygen permeable membranes were evaluated by gas chromatographic method. Homopolymers with short siloxane chains were found to be better than those with long branches in selectivity in permeation and mechanical strength. Introduction of fluorine atoms into polymer structure did not improve the selectivity in permeation.

Hydrogen bonds in 1-acyl-1,2-dimethylhydrazines of fluorocarboxylic acids

1. The molecules of 1-acetyl-, 1-trifluoroacetyl-, and 1-difluoroacetyl-1,2-dimethylhydrazines form hydrogen bonds, which remain in dilute solutions and, partly, in the gaseous state. 2. Associations in 1-acetyl-1,2-dimethylhydrazine are evidently realized with the participation both of the unshared electron pairs of the oxygen atom and of the nitrogen at position 2. 3. The introduction of fluorine atoms into the acyl fragment of the hydrazide molecule leads to the preferential formation of intermolecular hydrogen bonds of the N-H⋯N type. 4. The low probability of the formation of an intramolecular hydrogen bond of the N-H⋯ O=C type was demonstrated.

Fluorinated Analogues of Liquid Crystals 1. Analogues of 4-Methoxybenzylidene-4'-Butylaniline with Perfluorinated Alkyl- and Alkoxy-Groups

Abstract For the first time the MBBA analogues comprising of perfluorinated methoxy- and/or n-butyl groups have been synthesized and their mesomorphic properties have been studied. It has been shown that introduction of fluorine atoms into at least one of the substituents causes the appearance of a smectic mesophase, and that the compound comprised of both CF3O and n-C4F9- groups possesses no mesomorphic properties.

Aliphatic fluoro nitro compounds Communication 5. Proton magnetic resonance spectra and ionization constants of polyfluoronitroalkanes

1. The PMR spectra of a number of nitro compounds were studied. As in the case of other electronegative groups, the introduction of fluorine atoms into a nitroalkane molecule leads to a shift in the PMR signal of theα-hydrogen toward weaker fields. 2. Except in the case of the introduction of fluorine atoms, the change in the chemical shift of theα-hydrogen in the PMR spectra of nitroalkanes on introduction of electronegative substituents is related symbatically to the change in the ionization constants of these compounds. 3. The introduction of fluorine atoms in theβ-position relative to the nitro group increases the chemical shift of theα-hydrogen in the PMR spectrum and simultaneously increases the ionization constant of the nitro compound. The introduction of fluorine in theα-position leads to increase in the chemical shift of theα-hydrogen and lowering of the ionization constant.