| 2. Synthesis of partially fluorinated organic compounds using the reaction of internal perfluoroolefins with nucleophilic reagents.
Reactions of terminal perfluoroolefins with nucleophilic reagents have been studied in detail and play an important role in a synthesis of key intermediate products of organic synthesis. However, insufficient attention has been given to reactions of internal perfluoroolefins with nucleophilic reagents. At the same time, internal perfluoroolefins are of interest by themselves as they can be considered raw material for a synthesis of new organic compounds [1-8]. The assumption is based on the data of photoelectronic spectroscopy of the perfluoroalkyl group at double bond lower energy p-orbital, which promotes attack of nucleophile on the atom of carbon of this bond. The potentials of a reduction are the important characteristic of the olefinic system reactionary ability [14]. The size depends on the nature of the substituent at double bond and upon the transition from the substituent fluorine to polyfluoroalkyl, it is decreased. With the increase of the number of perfluoroalkylic groups at double bond, the potential of reduction is lowered, and the reactionary ability perfluoroolefins grows: (RF)2C=C(R2)2 > (RF)2C=CFRF > (RF)2C=CF2 , RFCF=CFRF > RFCF=CF2 > CF2=CF2. The fluorine polyfluoroalkyl group essentially stabilizes an intermediate carbanion [17-19]. All this causes the reactions between internal perfluoroolefins and nucleophilic by-reagents to have a decrease in reactivity in the series olefins and we can see that it corresponds to a decrease in the stability of the derived intermediate carbanions. However, in these reactions it is necessary to take into account the influence of the structure of internal perfluoroolefins. Factors influencing electron-affinity of the fluorinated alkenes, i.e. the influence of fluorine or perfluoroalkyl (RF) as a substituent at the double bond, are important for consideration, as are the effects of these substituents on intermediate carbanion stability. This is insufficient to account for the greater reactivity of perfluoropropene, as compared to perfluoro-2-butene because the corresponding intermediate {Nu-CF(CF3)-CFCF3}- can only have the stability marginally different from that of [NuCF2CFCF3]-. Perfluoropropylene oligomerixes readily produce a mixture of dimers and trimers in the presence of a base or fluorine ion. At the same time nucleophilic reactions of the dimers and trimers have been investigated by several researches. As to trimers, three isomers are known at present : perfluoro-3(1-methylethyl)-4-methylpent-2-ene, perfluoro-3-ethyl-2,4-dimethylpent-2-ene and perfluoro-2,4-domethylhept-3-ene (1).
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