Ronald Rowland

Fluoro-olefin chemistry Part 20 [1]. Reaction of hexafluoropropene with alcohols

Abstract Reaction of hexafluoropropene (HFP) with a series of alcohols under thermal, photochemical or peroxide-initiated conditions affords the 1:1 adducts CF3CHFCF2CR1R2OH (R1 = H, R2 = H, Me, Prn or CF3; R1 = Me, R2 = Me or Et) in high yield via a radical chain mechanism. Adduct are not formed with the alcohols (CF3)2CHOH and CF3CHFCF2CH2OH. Other 1:1 adducts of structure CHF2CF(CF3)CH2OH and CH3(C2H3CF2CHFCF3)CH2OH are formed as minor products in the methanol and n -butanol reactions, respectively.

Reaction of hexafluoropropene with halogenoalkanes

Abstract Insertion of hexafluoropropene under thermal and/ or photochemical conditions occurs into C-H bonds of the halogenomethanes MeCl, CH 2 Cl 2 , CHCl 3 , MeF, CH 2 F 2 and CHF 2 Cl and the fluoroethanes EtF, MeCHF 2 and MeCF 3 , into CH and CCl bonds of the monochloroalkanes EtCl, MeCHFCl, pr n Cl, pr i Cl, Bu t Cl and Bu i Cl and into CCl bonds of allyl chloride and the chloroalkanes CH 2 ClCH 2 Cl, MeCHCl 2 , CH 2 ClCHCl 2 and MeCCl 3 .

Carbene chemistry. Part 11. Insertion reactions of 1,2,2-trifluoroethylidene into carbon–hydrogen bonds of alkanes, cycloalkanes, and diethyl ether

1,2,2-Trifluoroethylidene, CHF2·F, readily inserts into C–H bonds in alkanes and cycloalkanes in the order tertiary > secondary > primary. The ease of insertion into C–H bonds of the same type varies according to their environment and is dependent on the number of β hydrogen atoms present; an adjacent oxygen atom is also effective in this respect as shown by the high reactivity of the secondary C–H bonds in diethyl ether. In a number of reactions cyclopropanes are also formed as minor products via dehydrogenation of the alkane to the corresponding alkene by the carbene, followed by addition of the carbene to the alkene.

Fluoro-olefin chemistry. Part IX. Thermal insertion of hexafluoropropene into carbon–hydrogen bonds in alkylbenzenes

The thermal reactions (ca. 250 °C) of the alkylbenzenes ArCH2R (Ar = Ph, R = H, Me, or Et; Ar =p-ClC6H4, R = H; Ar =p-MeC6H4, R = H) with hexafluoropropene give mainly the 1 : 1 adducts ArCHR·CF2·CHF·CF3, together with smaller amounts of the 1 : 1 adducts ArCHR·CF(CF3)·CHF2, 1-alkyl-2,2,3-trifluoro-3-trifluoromethylindanes, 1-alkyl-2,3,3-trifluoro-2-trifluoromethylindanes, and minor amounts of other products. Reaction at high pressure (autoclaves) favours 1 : 1 adduct formation whereas at lower pressure (tubes) indane formation is favoured. The reaction with cumene does not afford 1 : 1 adducts, the major products being 1,2,2,2-tetrafluoroethylbenzene, 1,1-difluoro-2-methylpropene, and the cyclobutane, [graphic omitted]F2; indanes are also formed in this reaction. Chlorination, bromination, and nitration of the 1 : 1 adduct PhCH2·CF2·CHF·CF3 gives the corresponding ortho- and para-substituted derivatives in the ratios 47 : 53, 20 : 80, and 0 : 100, respectively.

Fluoro-olefin chemistry. Part 16. Reaction of hexafluoropropene with n-butane and n-pentane

Thermal reaction of hexafluoropropene with n-butane at ca. 300 °C gives 1 : 1 and 2 : 1 adducts [major products CF3CHFCF2R; R = Bun(11), Bus(12), and CHMeCH2CH2CF2CHFCF3(14)], together with lower alkane adducts H [C3F6] R (R = Me, Et, Prn, and Pri) and 1,1,1,2,3,3-hexafluoropropane (4). The 1 : 1 adducts are precursors of the 2 : 1 adducts and the lower alkane adducts, and the structures of the isolated 2 : 1 adducts indicate that C–H bonds α- and β- to the fluoroalkyl group in the 1 : 1 adducts are deactivated towards hydrogen abstraction. It is proposed that the 1 : 1 and 2 : 1 adducts arise by a radical-chain mechanism initiated by hydrogen abstraction from n-butane and the 1 : 1 adducts, respectively, and that the lower alkane adducts are formed via interaction between the 1 : 1 adducts and excited hexafluoro-propene resulting in C–C bond fission. The photochemical and peroxide-initiated reactions give much higher yields of 1 : 1 and 2 : 1 adducts at the expense of the lower alkane adducts. Analogous products are formed in the thermal reaction with n-pentane [major 1 : 1 and 2 : 1 adducts CF3CHFCF2R; R = CHMePrn(16), CHEt2(17), CHMeCH2CHMeCF2CHFCF3(18), and CHMe(CH2)3CF2CHFCF3(19)], but, surprisingly, 2 : 1 adducts formed via hydrogen abstraction from the γ-C–H bonds (CH3) of the 1 : 1 adduct (17) are absent.

Cyclopropane chemistry. Part 4. The reactions of 1,2,2-trifluoroethylidene with alkenes and pyrolysis of the resulting cyclopropanes

1,2,2-Trifluoroethylidene, generated by the pyrolysis of (1,1,2,2-tetrafluoroethyl)trifluorosilane, reacts with tetrafluoroethylene, ethylene, and a series of methyl-substituted ethylenes to give the corresponding 1-fluoro-1-di-fluoromethylcyclopropanes in good yield; cyclohexene gives the corresponding norcarane, and tris(trifluoromethyl)phosphine gives the corresponding phosphorane (CF3)3[graphic omitted]·[graphic omitted]F·CHF2. Pyrolysis of 1,2,2,3,3-pentafluoro-1-difluoromethylcyclopropane affords difluorocarbene and 3H-pentafluoropropene, but pyrolysis of the methyl-substituted cyclopropanes results in the formation of dienes in high yield, e.g. the 1,4-dienes CHF:CF·CMeR·CMe:CH2 from the cyclopropanes [graphic omitted]F·CHF2(R = H or Me) or 1,3-dienes from the methyl-substituted cyclopropanes, e.g. [graphic omitted]F·CHF2→ CH2:CMe·C(CHF2):CH2. In certain cases further dehydrofluorination of the 1,3-dienes affords trienes, e.g. [graphic omitted]F·CHF2→ CH2:CMe·C(:CHF)·CMe:CH2.

Some aspects of the chemistry of chlorofluoro-olefins which contain allylic chlorine atoms

Abstract Routes to perflouroallyl chloride, CF2:CF.CF2Cl, and to cis -and trans -1-chloro-hexafluoro-2-trifluoromethyl(but-2-ene), (CF2Cl)(CF3)C:CF.CF3 are reported, and their susceptibility to attack by nucleophiles discussed; the allylic chlorine atoms in these olefins are the controlling factor in determining the products obtained. The conversion of 3-chloropentafluoropropene into a series of perfluoroallyl derivatives of general formula R.CF2.CF:CF2 [R = (CF3)3C-, CF3O-, C6F5-, l-, MeO-, etc.] is described, and the further chemistry of 3-chloropentafluoropropene and its derivatives outlined. Water reacts rapidly with (CF2Cl)(CF3)C:CF.CF3 to give CF2:C(CF3).CFCl.CF3 or CF3.CO.CH2.CF3. Methanol affords CF2:C(CF3).CFOMe.CF3 and (MeOCF2)(CF3)C:CF.CF3 as initial products, with subsequent secondary products such as CF3.CFOMe.CH(CF3).CF2OMe, (CF3)(MeO)C:C(CF3).CF3OMe, MeO.CF:C(CF3).CFOMe.CF3, (CF3)(MeO)CF.CH(CF3).CO2Me, and (CF3)(MeO)C:C(CF3).CO2Me. The influence of allylic chlorine and of reaction time on the formation of these products, and mechanistic pathways for their formation are considered.