Fluorination of polyhydrofluoroethylenes. I. Direct fluorination of poly(vinyl fluoride) film

It has been demonstrated that the poly(vinyl fluoride) film can be fluorinated by exposing the polymer to an environment of fluorine under atmospheric pressure and at ambient temperature. Fluorine content, infrared spectra, thermal properties, and solubilities in the polar solvents were investigated for the fluorinated products and the following results were obtained. In the case of films less than 10 μ in thickness, the fluorination appeared to proceed homogeneously. Under any fluorinating conditions applied, i.e., fluorine pressure of up to 800 mm Hg and temperatures of up to 90°C, the fluorine content never exceeded 65% which corresponds to a composition of C₂F_2.5H_1.5. The activation energy of the reaction was calculated to be 6.8 kcal/mole. The polymer reacted with a small amount of oxygen contained in the fluorine to form acyl fluoride groups. The fluorinated films became insoluble in boiling N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide, but colored gradually to a dark brown. The occurrence of some crosslinking in the products was revealed.     

Electrochemical fluorination of chlorine-containing ethers

The electrochemical fluorination of chlorine-containing ethers has been studied. In general, it was found that a chlorine bonded to an a-carbon atom in the ethers was readily removed during electrochemical reaction in anhydrous hydrogen fluoride, whilst a chlorine bonded to the β-carbon atom was retained to yield β-chlorinated polyfluoroethers.Through the use of this method, several new chloropolyfluoroethers, e.g. 2-chloro-1,1,2,2-tetrafluoroethyl difluoromethyl ether, 2,2-dichloro-1,1,2-trifluoroethyl trifluoromethyl ether 2,2-dichloro-1,1,2-trifluoroethyl difluoromethyl ether, 2,2-dichloro-1,1,2-trifluoroethyl chlorodifluoromethyl ether, 2-chloro-1,1,2,2-tetrafluoroethyl chlorodifluoromethyl ether and 2,2-trichloro-1,1-difluoroethyl trifluoromethyl ether, have isolated and characterized.     

A convenient synthesis of 6-, 7-, and 8-membered cyclic phosphodiesters

1,3-, 1,4-, and 1,5-Alkanediols are converted into the corresponding 6-, 7-, and 8- membered cyclic phosphodiesters in a two-step procedure utilizing N-(1,2-dimethylethylene-dioxyphosphoryl)imidazole ($\text{2}\text{?}$ as the sole phosphorylating reagent.     

The velocity of air bubble ascending in aqueous solution of surface active substance and inorganic electrolyte

Summary A series of measurements of falling velocities of glass sphere in an aqueous solution of sodium dodecyl sulfate and in pure water were carried out to elucidate the decrease in ascending velocity of air bubble in water due to the presence of surface active substance. From this, it was confirmed experimentally that the air bubble rises as a sphere and the air circulation inside the bubble is the sole factor in increasing rising velocity in the region of bubble radius from 0.03 to 0.07 cm, and that the circulation is actually suppressed by the adsorption of surface active substance. Measurements were also made on the ascending velocity of air bubble in aqueous solution of several inorganic substances as well as in tap water. The slight but distinct increase in rising velocity compared with that in distilled water was noted.

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Zusammenfassung Zur Erkl?rung des Mechanismus der Abnahme der Aufstiegsgeschwindigkeit einer Luftblase in Wasser durch Zusatz von grenzfl?chenaktivem Stoff wurde eine Serie von Messungen der Fallgeschwindigkeit einer Glaskugel in der betreffenden Flüssigkeit durchgeführt. Dies führt uns zum Schlu?, da? Luftblasen in genügend konzentrierten L?sungen sich genau wie feste Kugeln verhalten. Es wurde ferner die Zunahme der Aufstiegsgeschwindigkeit von Luftblasen mit Radien zwischen 0.03 und 0.07 cm in destilliertem Wasser und in verdünnten L?sungen von oberfl?chenaktiven Stoffen durch die Gasstr?mung im Inneren der Luftblasen erkl?rt. Diese Gasstr?mung wird um so schw?cher, je konzentrierter die L?sung ist. Die Behinderung der Gasstr?mung wurde der Absorptionsschicht an der Luftblase zugeschrieben. Die Aufstiegsgeschwindigkeiten von Luftblasen in L?sungen mit verschiedenen anorganischen Substanzen und in Stadtwasser zeigen geringe aber me?bare Zunahme.

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The author wishes to express her gratitude to Professor T. Sasaki for his kind direction and valuable criticism. The cost of this research has been defrayed from the grant of the Ministry of Education given to the professor.     

Enhancement of selectivity of a benzoate-sensitive liquid membrane electrode by alkylphenol

The selectivity of the benzoate-sensitive liquid membrane electrode based on tri-n-octylmethylammonium benzoate in o-dichlorobenzene enhanced is remarkably by the addition of p-t-octylphenol to the liquid exchanger solution. There is a linear relationship between the change in the logarithmic selectivity coefficient and the pK_a value of the aliphatic monocarboxylic acid interference. Large decreases in the selectivity coefficients are observed for ions having a small proton acceptor ability such as perchlorate and tri-fluoromethanesulfonate.     

Studies on the biosynthesis of corrinoids and porphyrinoids. I. The labeling of oxygen of vitamin B12

Recently the amide-oxygen has been suggested to participate in the formation of the corrin ring of vitamin B12. To confirm this hypothesis, 17O-labeled aminolevulinic acid (ALA) was prepared and administered to Propionibacterium shermanii. The isolated vitamin B12 showed only broad 17O signals in the oxygen-17 nuclear magnetic resonance (17O-NMR) spectrum. However, distinct isotope-shifted peaks were observed in the 13C-NMR spectrum of vitamin B12 isolated after incorporation of [1-13C:1,4-18O2]ALA. Of these shifted peaks, one peak (C27) showed very low intensity. This indicates that dilution of 18O occurred at the acetyl chain of the A ring of vitamin B12. This result supports the assumption that the lactone formation of the A ring promotes the ring contraction, as proposed by Eschenmoser.     

First examples of stable arenium ions from large methylene-bridged polycyclic aromatic hydrocarbons (PAHs). Directive effects and charge delocalization mode

In connection to a growing interest in developing structure/activity trends in nonalternant polyarenes, we report on the generation and NMR studies of the first series of persistent arenium ions from large methylene-bridged PAHs (mostly 22pi six-fused ring systems). Low-temperature protonation (FSO(3)H/SO(2)ClF) and model nitration (with HNO(3)/HOAc or NO(2)(+) BF(4)(-)) were used as mimic reactions for generation of biological electrophiles. The site(s) of protonation (and nitration) were determined as a function of PAH structure. Charge delocalization mode in the resulting arenium ions of protonation are assessed based on detailed low-temperature NMR studies at 500 MHz. Systems studied were 1-methylcyclopenta[def]phenanthrene 2, 11H-benz[bc]aceanthrylene 8, 5H-benzo[b]cyclopenta[def]chrysene 9, 13H-dibenzo-[bc,l]aceanthrylene 10, 13H-cyclopenta[rst]pentaphene 11, 4H-benzo[b]cyclopenta[mno]chrysene 12, 6H-cyclopenta[ghi]picene 13, 4H-cyclopenta[pqr]picene 14, 4H-cyclopenta[def]dibenz[a,c]anthracene 15. For comparison, dibenzo[a,c]anthracene 16 and dibenzo[a,h]anthracene 17 were also included (Figures 1 and 2). It is shown that the methano-bridge exerts a strong directive effect which diminishes as the bridge moves from the more central "inner" positions to more peripheral "outer" positions. Charge delocalization mode in the resulting carbocations are discussed based on the magnitude of Deltadelta (13)C values. Possible relationships with biological electrophiles formed by epoxide ring opening in the putative metabolites are also considered.     

Rapid synthesis of polyamide dendrimers from unprotected AB2 building blocks

A rapid synthetic method for the preparation of polyamide dendrimer without protection and deprotection steps has been developed. A symmetrically branched third-generation polyamide dendrimer was prepared by a convergent method involving activation of focal point with a condensing agent, diphenyl (2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonate (DBOP), followed by condensation of the active amide with the diaminocarboxylic acid 3,5-bis(4-aminophenoxy)benzoic acid as an AB2 building block.