The resonance Raman spectrum of the aniline radical cation

The time-resolved resonance Raman spectrum of the aniline radical cation has been observed using pulse radiolysis methods. This radical exhibits a large inverse secondary isotope effect on deuteration of the NH₂ group on the CN stretching frequency. Various spectral features indicate that this radical is structurally similar to the phenoxyl radical.     

Comment on the reported observation of the “raman spectrum of the phenoxy radical” in stopped flow experiments

Pulse radiolysis studies show that phenoxyl radical reacts at diffusion controlled rates. Concentrations on the time scale of stopped flow experiments cannot be substantially above 10^-5 M so that in the absence of resonance enhancement the Raman spectrum reported by Shindo and Hiraishi cannot be assigned to phenoxyl radical.     

Retardation of radical polymerization rate by phenoxy radical produced from T-butylperoxy phenylcarbonate

T-butylperoxy phenylcarbonate (BPPC) was prepared. Its decomposition rate constant in cumene is given by k_d = 2.39 × 10¹⁵ exp(?17,300/T), where T is the absolute temperature. When BPPC decomposes to polymerize styrene at 100°C, it produces 12% phenoxy radical to total primary radicals. The phenoxy radical hardly adds to styrene and reacts the other primary radicals and polymer radical. Thus it retards the rate of polymerization.     

Raman spectrum of difluorodiazirine

The Raman spectrum of difluorodiazirine has been re-examined. Four well-defined bands have been found in the low frequency region, which lead to a definitive assignment for all nine vibrational fundamentals of this molecule. The fundamental frequences are (in cm⁻¹): (a₁) 1563, 1282, 805, 502; (a₂) 451; (b₁) 1248, 481; (b₂) 1091, 544.     

ESR spectrum of the cyclopropenyl radical

The ESR spectrum of a radical produced by photolytically generated t-butoxy radicals and cyclopropene in solution is reported. Arguments are presented for an assignment of the spectrum to the cyclopropenyl radical (CH)₃ undergoing fast exchange between equivalent distorted r_e structures.     

The Raman spectrum of propynal

The Raman spectrum of propynal as a vapour and dissolved in various solvents were recorded. These data and the observed polarization measurements were in accordance with the fundamental frequencies assigned to the ground state of this molecule. The vibrational modes of propynal were compared with those previously reported for the halopropynals.     

Raman spectrum of propylene carbonate

The Raman spectrum of propylene carbonate (4-methyl-1,3-dioxolan-2-one) has been recorded and analyzed. Vibrational assignments have been made for many of the observed frequencies on the basis of comparison with accepted assignments for certain vibrational modes in other compounds with close structural similarities.The spectra of propylene carbonate (PC)-water mixtures have been studied over the entire concentration range at 80° and there seems to be little or no interaction except for partial disruption of hydrogen bonding in water by PC. Raman spectra of solutions of LiClO₄ in PC and in PCH₂O mixtures indicate possible salvation of the Li⁺ ion.     

Molecular modeling studies of the reactions of phenoxy radical dimers: pathways to dibenzofurans

The B3LYP hybrid density functional computational technique was applied to describe the sequence of phenoxy radicals coupling reactions leading to the formation of dibenzofurans. Reaction kinetic parameters were estimated for key reactions. Aromatization of bis-keto dimers of phenoxy radicals followed by intermediate dehydration or dehydroxylation was demonstrated to be a strongly stereoselective process. While the S,S-diastereomer of the ortho-C//ortho-C keto dimer forms (o,o')-dihydroxybiphenyl, a known dibenzofuran intermediate, via inter-ring hydrogen transfer reaction, the less stable R,S-stereoisomer can easily be transformed into another 5-hydroxyl-4,5-cyclohexadiene-2,3-benzofuran intermediate that provides an energetically more favorable pathway for formation of dibenzofuran. The possible channels of radical-chain processes that convert these intermediates to dibenzofuran and polychlorinated dibenzofurans are discussed.     

The resonance Raman spectrum of azulene

Excitation profiles have been measured for three Raman lines of azulene in CS₂ solution in the spectral range of the visible absorption system, viz. 665—570 nm. The results are unexpected in as much as the excitation profiles do not exhibit maxima at or near the absorption peaks. The results are interpreted on the basis of contributions to the A-term by other modes than the one studied in the Raman effect. These terms give rise to interferences which lower the excitation profile in some regions while causing maxima at other frequencies.     

The ESR spectrum of the cis-stilbene radical anion

The ESR spectrum of the cis-stilbene radical anion has been observed under conditions where its conversion into the trans isomer is relatively slow. Assignment of the proton coupling constants has been based on studies on the 4,4′- and 7,7′- dideuterio derivatives, as well as on comparison with structurally related species. The values for the radical anions of cis- and trans-stilbene are very similar, except those (2.68 and 4.49 G, respectively) arising from protons in the 7,7′-positions. The difference is attributed to strong distortions of the π-system in the C1C7′C1′ fragment of the cis isomer.     

Absorption spectrum and kinetics of the acetylperoxy radical

The UV absorption spectrum of acetylperoxy radicals, produced in several photochemical systems, has been investigated using the molecular modulation technique. Rate coefficients were determined at 28 and 715 Torr for the reaction CH₃COO₂ + NO₂(+M) → CH₃COO₂NO₂(+M), which exhibits a pressure dependence.     

The far-infrared rotational spectrum of the CF radical

The rotational spectrum of CF in its ground electronic state was studied around 1000 GHz, using a tunable far-infrared source. Seven transitions were observed originating from the ²Π_1/2 and ²Π_3/2 substates. The hyperfine and Λ-type splittings were resolved. The results were combined with gas-phase electron resonance and infrared diode laser spectra to determine all pertinent molecular constants.     

Electronic spectrum of jet-cooled cyanocyclopentadienyl radical

The D₁-D₀ electronic spectrum of jet-cooled cyanocyclopentadienyl (C₅H₄CN) radical, produced by excimer laser photolysis of 1,3-cyclopentadiene-1-carbonitrile (C₅H₅CN), was measured by laser-induced fluorescence (LIF). The LIF spectrum was identical to that of radicals produced by photolysis of phenyl isocyanate and o-chloroaniline, which had been assigned to phenyl nitrene. This result shows that the nascent radical product in the photolysis of o-chloroaniline and phenyl isocyanate is isomerized to C₅H₅CN and the final product of C₅H₄CN radical is derived via the second photolysis. The rotational contour of the 0-0 band of the C₅₄CN radical, at 27143 cm⁻¹ (368.3 nm), is also presented. The electronic transition is A-type and π electron transition, and the symmetry of both the ground and excited electronic state is ²B₁ (of the C_2v point group).