The Chemistry of Alkenes.

The “through-space” mechanism in spin spin coupling

Fluorine chemical shifts

The spectra of several fluorine‐substituted, saturated, organic compounds have been investigated. It has been found that the coupling constants between 1,2 fluorine atoms are usually near zero. The coupling constants between 1,3 fluorine atoms in a free chain are usually between 7 and 10 cps if all of the intermediate skeletal atoms are carbon atoms. If one of the intermediate skeletal atoms is a nitrogen atom, these coupling constants go up to between 10 and 17 cps. The coupling constants between 1,4 fluorine atoms are usually in the range 2–7 cps when a nitrogen atom is in the intermediate skeletal chain. Rings usually reduce all coupling constants below the above stated values.Several exceptions are found to these generalizations. These generalizations with their exceptions lead the authors to believe that in the case of coupling between fluorine atoms, the main effect is not through‐the‐bonds, but rather a direct‐through‐space interaction. It is demonstrated that the restricted rotation about the carb...

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Nmr fluorine-fluorine coupling constants ii saturated organic compounds

The mechanism of ketene−diene reactions has been studied both experimentally and theoretically. Careful experiments of the reactions of diphenylketene (1) with cyclic (s-cis) 1,3-dienes [cyclopentadiene (2) and cyclohexa-1,3-diene (3)] lead to the first direct detection of the Diels−Alder cycloadducts (10 and 11) by low-temperature NMR spectroscopy. The initially formed cycloadducts are converted to the final Staudinger products, cyclobutanones (6 and 7), by [3,3] sigmatropic (Claisen) rearrangements. In contrast, ketene 1 reacts with open-chain 1,3-dienes [2,3-dimethyl-1,3-butadiene (4) and 1-methoxy-1,3-butadiene (5)] to afford initially both the Staudinger-type (8, 9) and Diels−Alder-type cycloadducts (12, 13). The Staudinger cycloadducts (8, 9) are converted eventually to Diels−Alder products (12, 13) by the retro-Claisen rearrangement. Thus, ketene recognizes dienes in cycloadditions as ketenophiles different from olefins. [4 + 2] and [2 + 2] cycloadducts are generated and can be intermediates or pro...

Ketene Recognizes 1,3-Dienes in Their s-Cis Forms through [4 + 2] (Diels−Alder) and [2 + 2] (Staudinger) Reactions. An Innovation of Ketene Chemistry

Hexafluoropropene trimer. Synthesis and properties of functional derivatives

Bis(trifluoromethyl(Ketene—VIII

1.

The interaction of perfluoroisobutylene oxide with ammonia and dimethylamine leads to dimethylamides ofα-aminoperfluoroisobutyric acids.




2.

The isomerization of perfluoroisobutylene oxide is a convenient comparative method for the production of perfluoroisobutyryl fluorides.

Derivatives of perfluoroisobutyric acid

1.

A number of saturated fluorine-containing ethers was synthesized by photochemical chlorination.




2.

The chlorination of 2,4-bis(trifluoromethyl)-3-methoxy-1,1,1,5,5,5-hexafluoro-2-pentene proceeds as the replacement of one hydrogen atom of the methyl group by chlorine and the subsequent addition of chlorine to the double bond, which leads to the formation of 1,1,3,3-tetrakis(trifluoromethyl)chloroacetone.




3.

When ethers, containing the -CF2OCCl3 group, are treated with antimony trifluoride the chlorine atoms are smoothly replaced by fluorine. At the same time, ethers containing the -CFClOCC13 group undergo decomposition as the result of cleavage of the C-O bond.

Some reactions of fluorine-containing ethers

1.

When the appropriate ethers containing fluorinated groups react with sulfuric acid or aluminum halides, 2-hydro- and 2-halo-hexafluoroisobutyryl halides are obtained.




2.

It was shown that in the fluorocarbonyl group of the acid fluorides obtained fluorine can be smoothly replaced by chlorine or bromine by the action of the appropriate aluminum halide.




3.

Perfluorodimethylketene is formed in the pyrolysis of perfluoroisobutenyl methyl ether.

Yu. A. Cheburkov

Papers

Hexafluoropropene trimer. Synthesis and properties of functional derivatives

Bis(trifluoromethyl(Ketene—VIII

Derivatives of perfluoroisobutyric acid

Some reactions of fluorine-containing ethers

Perfluorodimethylketene and perfluoromethacrylic acid Communication 1. Hexafluoroisobutyryl chlorides from fluorinated ethers