2.2.2. New in the Oxidization Processes of Perfluoroolefines Double Bond up to  Perfluoroalkancarboxylic Acids.

The oxidization processes of perfluoroalkyl ethylene and propylene derivatives proceed mostly easy, that is studied rather widely. The oxidization of internal perfluoroolefines proceed at more severe conditions. Thus, acting of such oxidizers as potassium permanganates and ruthenium tetraoxide affect the multiply bond and, as a rule, after hydrolysis two perfluorinated carboxylic acids are formed [63].

It is known, that when only the perfluoroalkyl substituents have a multiply bond, the oxidization using potassium permanganate will result exclusively in formation of diol [64].

Analogously the heating of R₂C=C(CF₃)₂ [R = CF₃, C₂F₅] together with KMnO₄ in aqueous acetone produces diol HOCR₂C(CF₃)₂OH, and perfluoro(1-ethyl-2-isopropylcyclopentene) results in formation of diketone C₂F₅C(O)(CF₂)₄C(O)CF(CF₃)₂ [64]. At KMnO₄ action dialkyl substituted fluoroolefines of C4 - C7 type and perfluorocyclohexene turn into -diketones with 40-50% yield [64,65]. Trans-isomers much easily react with KMnO₄, than the corresponding cis-isomers.

At the same time the oxidization of trialkyl substituted fluorolefines using the same reagent results in formation of -hydroxyketones [66-69].

Chromium trioxide in fluorosulphonic acid shows strong oxidizing properties. Thus this oxidizing system influencing hexafluoropropylene produces hexafluoropropylene oxide with the yield of 55% [70]. At the same time the addition of Cr₂O₃ to this system results in formation of fluorosulphinate pentafluoroacetonyl. 

The oxidization of perfluoroalkylethylens (RCH=CH₂, R = perfluoroalkyl C2-C14) multiply bond goes most easily at oxidization using sodium hypochlorite NaOCl in the presence of RuO₂ *7H₂O in organic dissolvent (tert-buthanol, MeCN, diglyme, 1,3-dioxane). For example, at 30 ^oC and atmospheric pressure C₈F₁₇CH=CH₂ turns into perfluoroctylcarboxylic acid C₈F₁₇COOH in 3 hours with the yield of 98 % [71]. 

2.2.3. The Oxidization of Telomeric Alcohols.

Telomeric alcohols like H(CF₂CF₂)nCH₂OH (where n = 1-8) can be oxidized up to corresponding -hydroperfluorocarboxylic acids, playing a great part in the creation of different fluorine materials of practical purpose. The oxidization of telomeric alcohols is carried out by action of potassium permanganate, nitrogen oxides, Chromium anhydride, chlorine at 100-140 ^oC and UV irradiation. However these methods have essential disadvantages and production technologies on their base are not developed. There by researchers still keep an eye on telomeric alcohols oxidization processes.

Thus, telomeric alcohols (C1-16) are oxidized by nitric acid in the presence catalysts, which are the oxides and salts of ferrum, nickel, cuprum and vanadium [72]. At oxidization of H(CF₂)₈CH₂OH using 55 % nitric acid together with synchronous oxygen introduction at 125 ^oC and pressure of 0.8 MPa in the presence of FeCl₂*.nH₂O in 7 hours at 100 % alcohol conversion H(CF₂)₈COOH is formed with yield of 99.6 % [72].

Catalytic system, containing complexes of divalent cuprum, catalyses selective oxidization of telomeric alcohols up to perfluorocarboxylic acids [73,74]. This method is especially effective for alcohols with long carbon chain (C8-14). The process goes in alkaline medium, which is necessary for conversion of alcohol into anionic form, that greatly facilitates activization of molecular oxygen at low temperatures. 

Obviously, the participation of cuprum complexes in electrone transferring from alcoholates ions onto oxygen allows the reaction to go according to thermodinamically advantageous dielectron mechanism, that determines abnormally high rates of oxidization. The  reaction rate almost doesn't depend on molecular mass of oxidized alcohols in the interval n = 1 - 6. The variation of reaction carrying out conditions (temperature, dissolvent, ligand, concentration of alkaline and catalyst etc.) allows to oxidize selectively (with 100%) the telomeric alcohols. For example, HCF₂CF₂CH₂OH is oxidized using molecular oxygen in the presence of cuprum catalyst and alkaline agent (in the presence of 5* 10³ M CuCl₂ solution and 1.10-2 ? ortho-phenanthroline solution in isobutyl alcohol and NaOH at 45 ^oC, 6.5 h) with the yield of 73.8 % up to HCF₂CF₂COOH (conversion 50.5 %).
The oxidization of telomeric alcohols H(CF₂)nCH₂OH (n = 2, 4, 6) in liquid phase using air oxygen at 350 ^oC in the presence of V₂O₅ results in formation of H(CF₂)nCH(OH)₂ with the yield equal 74-93 % [75]. Other catalysts may be also used [76].
The authors of works [77-79] had developed the approach to the synthesis of 3-chlorotetrafluoropropionic acid using photochemical chlorination of  borate and phosphate esters of telomeric alcohol HCF₂CF₂CH₂OH. 

The chlorine action is carried out at UV-irradiation (lamp 100-400 watt) at 25-110 ^oC, at that further substitution of - and - atoms of alcohol hydrogen can happen. The decomposition of chlorinated borate passes at reaction conditions up to acid chloroanhydride, while chlorinated phosphates require higher temperatures (180-250 ^oC). At the same time the chlorine action on telomeric alcohols in the presence of catalyst results in formation of 1-chloroperfluoroalkanes [78].

The telomeric alcohols have two reaction centers, according to which the reactions can be carried out. The telomeric alcohols reactivity in reactions, passing affecting the alcoholic group is discussed above. At the same time the existence of CHF₂ fragment at the end of carbon chain allows to expect the turning with its active participation. First of all, the existence of fluorine atoms and the influence of CF₂ fragment next to it results in acidity increasing and thereafter the increasing of carb-anion generation possibility. Indeed, the action of two gram-molecules of alkyllithium results in multiply terminal bond formation. It allows, for example, to develop trifluoroacrylic acid obtaining method out of 2,2,3,3-tetrafluoropropanol [80]. 

Partly fluorinated alcohols with -CH₂CH₂OH fragment oxidize rather easily at Jones conditions (oxidization of CrO₃ in sulphuric acid) [81]. It is important, that in this case the unsaturated acid is obtained, which contains fluorine atom rather active regarding nucleophiles at internal multiply bond. This is used for synthesis of different heterocyclic compounds and tertiary amines. In case of oxidization of alcohols like R_FCF₂CH₂CH₂OH (R_F = C₅F₁₁, C₇F₁₅, C₉F₁₉) by CrO₃ in sulphuric acid the formation of saturated acids R_FCF₂CH₂COOH is possible, which are also used for synthesis of heterocyclic compounds [82a,b].

Perfluorinated carboxylic acids F(CF₂)nCOOH (n = 1-5) are obtained with high yield and selectivity at acting on partly fluorinated fluoroparafines F(CF₂)nCH₃ of chlorine or other oxidizing agent at UV-irradiation (2000-14000-A light) [82c].
Analogously, [83,84] unsaturated alcohol (Z+E) is obtained out of H(CF₂CF₂)₅CH₂OH by BuLi acting, which is oxidized using ozone in CF₃CH₂OH medium up to corresponding acid.

The opportunity of the terminal multiply bond generation can be also used in other purposes.