2599-73-7Relevant academic research and scientific papers
Kinetic Study for Reactions of Nitrate Radical (NO3.) with Substituted Toluenes in Acetonitrile Solution
Ito, Osamu,Akhido, Seiji,Iino, Masashi
, p. 2436 - 2440 (2007/10/02)
The absolute rate constants for the reactions of the nitrate radical (NO3.) with substituted toluenes in acetonitrile have been determined by the flash photolysis method.From the plots of the rate constants against the ionization energies, it was revealed that the reaction path for toluene derivatives with low ionization energies is different from that for toluene derivatives with high ionization energies.For toluene, a deuterium isotope effect was observed to be ca. 1.6, suggesting the direct hydrogen atom abstraction reaction; in this group, xylenes and p-chlorotoluene belong.For toluene derivatives with electron-withdrawing substit uents, NO3. may add to the phenyl rings followed by successive reactions.For both groups, linear correlations against ionization energies with negative slopes show that NO3. is highly electrophilic and that strong polar effects exist in the transition states of both reactions.For toluenes with methoxy groups, the electron-transfer reaction from methoxytoluene to NO3. is a main initial path, since the transient absorption band due to the cation radical of methoxytoluene was detected.
Substituent Effects on Benzyl Radical ESR Hyperfine Coupling Constants. The ?α*Scale Based upon Spin Delocalization
Dust, Julian M.,Arnold, Donald R.
, p. 1221 - 1227 (2007/10/02)
The electron spin resonance spectra of 21 para- and meta-substituted benzyl radicals have been analyzed.A substituent constant, ?α*, has been defined from the benzylic α-hydrogen hyperfine coupling constant.The ?α* constant reflects the component of energy that may be attributed to spin delocalization in a substituted benzyl radical in comparison to the unsubstituted radical.For the derivatives studied, para substitution is stabilizing, except when fluorine is the substituent; meta substitution destabilizes the benzyl radical.A series of radical reactions is reexamined with an extended Hammett relation.The relative importance of spin delocalization vs. polar effects is assessed by the ratio of ρ* to ρ.The importance of choosing substituents for which ?a* and ? differ widely for such an assessment is emphasized.
Carbon-Hydrogen Bond Dissociation Energies in Alkylbenzenes. Proton Affinities of the Radicals and the Absolute Proton Affinity Scale
Meot-Ner (Mautner), Michael
, p. 5 - 10 (2007/10/02)
Rate constants (k) were measured for proton-transfer reactions from alkylbenzene ions RH+ to a series of reference bases B, i.e., RH+ + B -> BH+ + R*.For exothermic reactions (ΔH -1.For example, the reaction C6H5CH3+ + B -> BH+ + C6H5CH2* is fast (reaction efficiency = k/kcol >/= 0.5) when B = MeO-t-Bu or stronger bases, but k/kcol is significantly smaller when B is n-Pr2O or weaker bases.From the falloff curve of reaction efficiency vs.PA(B), we find PA(n-Pr2O) = PA(C6H5CH2*) + 0.8 kcal mol-1 = 200.0 kcal mol-1.Since PA(C6H5CH2*) is obtained from known thermochemical data, this relation defines the absolute PA of n-Pr2O.Through a ladder of known PA, we then obtain PA(i-C4H8) = 186.8 kcal mol-1; we also obtain the absolute PAs of other oxygen bases.Falloff curves of reaction efficiencies of 3-FC6H4CH3+, C6H5C2H5+, C6H5-n-C3H7+, and C6H5-i-C3H7+ with these reference bases give then the following PAs of R* and R-H bond dissociation energies (Do) (all in kcal mol-1) as R*, PA(R*), Do(R-H): 3-FC6H4CH2*, 197.2, 89.4; , 197.9, 86.2; , 199.1, 86.1; , 199.6, 86.1.In similar manner, rate constants for H+ transfer from C6H5NH2+ to reference pyridines and amines yield PA(C6H5NH*) = 221.5 and Do(C6H5NH-H) = 85.1 kcal mol-1 (1 kcal mol-1 = 4.18 kJ mol-1).
