Cyanomethyl radical

Table IR acetonitrile. spectra and force constants of the free cyanomethyl radical" and ...

Table 6.11 Calculated radical stabilization energies at 0 K for the cyanomethyl radical (kJ/mol).8...

Table 6.19 Comparison of experimental barriers at 0 K (kJ/mol) for the addition of cyanomethyl radical CI CN to alkenes CH2=CXY with those calculated with wavefunction-based electronic structure methods.a...

Calculated barriers for a selection of cyanomethyl radical additions are presented in Tables 6.19 and 6.20. The CBS-RAD method performs particularly well (MAD of 1.3 kJ/mol) for the selected cyanomethyl radical additions. However, the other levels of theory show somewhat larger mean absolute deviations (5.9 - 14.8 kJ/mol). With the exception of CBS-RAD (MD of -0.9 kJ/mol), all levels give higher barriers than those observed experimentally (MD of +5.9 to +14.8 kJ/mol). The correlation with experiment (R2 = 0.76 - 0.85) is somewhat poorer than that for the methyl and hydroxymethyl radical additions (Tables 6.15 - 6.18). 

Table 6.21 Overall performance of selected methods in predicting barriers for the addition of methyl, hydroxymethyl and cyanomethyl radicals to substituted alkenes. ...

CH4, and H2 while minor products such as HCCCN, H2C=CHCN, C2H4 and C4H2 were also detected. Ab initio chemical calculations revealed that the pyrolysis of acetonitrile is initiated by CH bond fission, forming a cyanomethyl radical. Products such as HCCN and H2C=CHCN have been shown to arise from the decomposition of succinonitrile, that forms by the recombination of two cyanomethyl radicals. The kinetics of thermocyclization of 2,3-diethynylquinoxaline (109) (Bergman cyclization) have been studied in various solvents. Non-polar solvents give shorter half-lives and better yields. The cyclization rates observed were found to be solvent dependent. ... 

Related trends are seen in data for radicals with functional group substituents. Hydroxymethyl and 2-hydroxy-2-propyl radicals show nucleophilic character. The hydroxymethyl radical shows a slightly enhanced rate toward acrylonitrile and acrolein, but a sharply decreased rate toward ethyl vinyl ether. The more electrophilic cyanomethyl radical shows reactivity enhancement not only with radical-stabilizing EWGs, but also with ERGs. Table 11.7 gives some of the reactivity data. 

The interaction between acetonitrile and iridium(O) complex generated elec-trochemically produces iridium(I) hydride and cyanomethyl radical [28a]. The... 

The thermal and photochemical reactions of (356 R = Bu or Ph) with (Me3Si)2Hg or (Me3Ge)2Hg gave N-metallated diaziridinyl radicals.From irradiation at A 400 nm, (356 R = Ph) gave the tetrazinyl radicals (357 M = Si or Ge), probably through diazirinyl radicals. A theoretical study of the diazirinyl radical and of the isoelectronic cyanomethyl radical indicates that both may exist in cyclic and open forms. 

In another example, 2,6-dimethyIbenzenediazonium tetrafluoroborate D(2,6-Me)2 is reduced by electrochenustry in an ACN solution to the corresponding radical. This 2,6-dimethylphenyl radical cannot attach to surfaces due to the steric hindrance of the two methyl groups [178]. Instead, it abstracts a hydrogen atom from CHjCN to give the cyanomethyl radical CHjCN that reacts with the surface (Au, Cu, Si) as indicated in Figure 3.73 [24]. Further reaction of the CH2CN carbanion, obtained... 

---