Free radical addition to olefins. Part 20.—A reinvestigation of the addition of methyl radicals to fluoroethylenes.

Abstract

The addition of methyl radicals to fluoroethylenes has been reinvestigated using both azomethane and di-t-butylperoxide as initiators. As in the previous work, excess methyl iodide was added to promote a chain reaction. Unlike the previous study, telomeric products of low volatility were identified and quantitatively estimated. Correction of the monomeric product ratios by addition of the appropriate telomers had a significant effect on the relative Arrhenius parameters in some cases. New values of the activation parameters for the addition of methyl radicals to vinyl fluoride, 1, 1difluoroethylene, trifluoroethylene and tetrafluoroethylene relative to ethylene, are presented.

Cyclization reactivities of fluorinated hex-5-enyl radicals

“…Bu n 3 SnH a reducing agent. The ratios of products 5 : 3 and 6 : 3 were determined directly by 19 F NMR analyses of the respective product mixtures. In determining each rate constant, six values of k C5 /k H and/or k C6 /k H were determined for six different concentrations of reducing agent using eqns.…”

“…Such a small kinetic effect of olefinic fluorine substituents on alkyl radical addition reactions is consistent with Tedder and co-workers' early studies on methyl affinities (Table 2), where the range of reactivities for the addition of a methyl radical to ethylenes with varying fluorine content is also relatively small. 6, 19 A single fluorine substituent at C-5 (as in radical 2b) causes a significant, 10-fold decrease in rate constant. This decrease no doubt derives largely from the steric/electrostatic influence of the 5-fluoro substituent, an effect which would be expected from virtually any substituent at the 5-position.…”

“…No double bonds were detected in the polymer by IR analysis. Unfortunately, the polymer (T g 106-113, T m 258-260 ЊC by DSC, second heat) was not soluble in organic solvents so it could not be fully characterized, but a high temperature 19 F NMR spectrum could be acquired for the melt. No vinyl fluorines were present and only saturated fluorine resonances appeared as multiplets at δ Ϫ103.5-130.6, a singlet at δ Ϫ163.5, a broad multiplet at δ Ϫ181.0 and a singlet at δ Ϫ187.7.…”

Mn2(CO)10‐Visible Light Photomediated, Controlled Radical Polymerization of Main Chain Fluorinated Monomers and Synthesis of Block Copolymers Thereof

“…Thus, while IDT catalysis would lead to PDI decrease [3,9], control experiments [51] reveal that, consistent with PVAc-IDT [101,102], the photochemically inactive [136a] Mn(CO) 5 -I is incapable of donating I. Although R F -Mn(CO) 5 (R F CH 2 F, CF 2 H) [136b] derivatives exist, organometallic CRP mediation with PVDF-Mn(CO) 5 via reversible C-Mn bond homolysis is discounted in view of the observed -I, not -H or -Mn(CO) 5 chain ends, of the successful CRP with catalytic, not stoichiometric Mn 2 (CO) 10 vs. R F -I, and of the relative order of the R F -Mn(CO) 5 (34) [74] < (CO) 5 Mn-Mn(CO) 5 (38) [132b] < R F -I (48) [137] < I-Mn(CO) 5 (54) [132] BDEs (kcal/mol), consistent with the photoinstability of Mn alkyls [132b].…”

“…To date, the most successful approach to FM-CRP [1] remains the iodine degenerative transfer (IDT) [3,[9][10][11][12][13][14] (IDT: P n • + P m -I ⇌ P n -I + P m • ) [1,15,16], an outcome of the earlier research on the high temperature (100-230 • C) free radical VDF telomerization [17,18] with polyhalides [19], especially (per)fluorinated iodo chain transfer (CT) agents [16] such as CF 3 I [20][21][22][23], CF 3 CF 2 I [24], CF 3 (CF 2 ) 3 I [25,26], CF 3 (CF 2 ) 5 I [21,[27][28][29], (CF 3 ) 2 CF I [26], Cl CF 2 CFCl I [23], I (CF 2 ) 4-6 I [10, 29,30], but also with less active HCF 2 CF 2 CH 2 I [27,28], C 6 F 13 CH 2 CF 2 I [28,31], and even CH 2 I 2 [32], R F CH 2 CH 2 I [33], or CH 3 I [34]. In fact, IDT may be one of the oldest CRP methods, as a linear dependence of M n on polymer yield was already demonstrated ] in the early 1980s, and was the first industrial implemented CRP protocol [10][11][12][13][14].…”