Excited-state and ground-state reactivities of para-substituted benzyl radicals toward molecular oxygen

Tokumura, Kunihiro; Ozaki, Tomomi; Nosaka, Hideyo; Saigusa, Yoko; Itoh, Michiya

doi:10.1021/ja00013a037

Cited by 58 publications

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“…This molecule has been reported to yield the p-methoxybenzyl radical. 6,8 The same fluorescence band ͑with the same life-time͒ as in Fig. 1 is observed by excitation with the 308 nm pulse.…”

Section: A Identification Of Radicalsupporting

confidence: 69%

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Photodissociation of C–H and C–O bonds of p-methoxytoluene and p-methoxybenzyl alcohol in solution

Fujiwara

Toyomi

1997

The Journal of Chemical Physics

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Picosecond real time study of the bimolecular reaction O ( 3 P)+ C 2 H 4 and the unimolecular photodissociation of CH 3 CHO and H 2 COThe photodissociation of p-methoxytoluene and p-methoxybenzyl alcohol at 266 nm in n-heptane solution is studied by nanosecond fluorescence and absorption spectroscopy. The formation of a p-methoxybenzyl radical is identified by its fluorescence which is induced by excitation at 308 nm. The yields of the radical are of the order of ϳ10 Ϫ3 for dissociation of p-methoxytoluene and p-methoxybenzyl alcohol. The growth rate of 1.5ϫ10 8 s Ϫ1 for the radical is equal to the decay rate of (1.5Ϯ0.3)ϫ10 8 s Ϫ1 for the precursor fluorescence in dissociation of p-methoxytoluene, whereas the growth rate of Ͼ1.0ϫ10 9 s Ϫ1 for the radical is much faster than the decay rate of (1.8Ϯ0.3) ϫ10 8 s Ϫ1 for the precursor fluorescence in dissociation of p-methoxybenzyl alcohol. The formation of the radical depends linearly on the photolysis pulse fluence for dissociation of p-methoxytoluene and p-methoxybenzyl alcohol. The data show existence of two distinct dissociation channels. p-Methoxytoluene dissociates from thermally equilibrated levels of the S 1 state after vibrational relaxation, whereas p-methoxybenzyl alcohol dissociates from vibrationally excited levels of the S 1 state in competition with vibrational relaxation. The difference of these channels is explained on a model of electronic coupling between the precursor and product states in the geometry where the C-H and C-O bonds are stretched in a plane perpendicular to the benzene rings. For p-methoxytoluene, the S 1 state does not correlate adiabatically to the ground state of the C-H bond fission products, so intersystem crossing or internal conversion precedes dissociation. For p-methoxybenzyl alcohol, avoided crossing between the * ͑benzene͒ configuration and the np(O)*(C-O) repulsive configuration results in the adiabatic potential-energy surface which evolves to the ground state of the C-O bond fission products allowing rapid dissociation.

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Section: A Identification Of Radicalsupporting

confidence: 69%

“…An absorption band is recorded at 288 nm, which is associated with the p-methoxybenzyl radical. 6,8,9 The fluorescence and absorption bands disappear at a 100 s delay.…”

Section: A Identification Of Radicalmentioning

confidence: 99%

Photodissociation of C–H and C–O bonds of p-methoxytoluene and p-methoxybenzyl alcohol in solution

Fujiwara

Toyomi

1997

The Journal of Chemical Physics

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“…1 Upon excitation with a 308 nm laser pulse, the dibenzyl ketone precursors gave transient absorptions around 317 nm, the 2 2 A 2 2À X 2 B 2 absorption band of the benzyl radical chromophore. 6,17 Dissociation of dibenzyl ketone triplets is known to be fast 3 and generally occurs within the duration of the laser pulse, producing one equivalent of benzyl radical. 4,5 This results in an initial 'step' feature in the decay traces ( Fig.…”

Section: Resultsmentioning

confidence: 99%

Aryl substituent effects and solvent effects on the decarbonylation of phenacetyl radicals

Zhang

Nau

2000

J. Phys. Org. Chem.

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“…The 3,4-dimethoxy substrate 2v gave trichlorides 5v and 6v in a combined 67% yield, or in 91% yield based on the loading of 1b (Scheme 5). These anomalous outcomes were again rationalized as resulting from the stabilization of radical intermediates gained upon methoxy substitution [51], which permitted further chlorination of either the methyl or arene groups.…”

Section: Resultsmentioning

confidence: 99%

Chlorination of phenylallene derivatives with 1-chloro-1,2-benziodoxol-3-one: synthesis of vicinal-dichlorides and chlorodienes

Zhao¹,

Murphy²

2018

Beilstein J. Org. Chem.

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Allyl and vinyl chlorides represent important structural motifs in organic chemistry. Herein is described the chemoselective and regioselective reaction of aryl- and α-substituted phenylallenes with the hypervalent iodine (HVI) reagent 1-chloro-1,2-benziodoxol-3-one. The reaction typically results in vicinal dichlorides, except with proton-containing α-alkyl substituents, which instead give chlorinated dienes as the major product. Experimental evidence suggests that a radical mechanism is involved.

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Excited-state and ground-state reactivities of para-substituted benzyl radicals toward molecular oxygen

Cited by 58 publications

References 0 publications

Photodissociation of C–H and C–O bonds of p-methoxytoluene and p-methoxybenzyl alcohol in solution

Photodissociation of C–H and C–O bonds of p-methoxytoluene and p-methoxybenzyl alcohol in solution

Aryl substituent effects and solvent effects on the decarbonylation of phenacetyl radicals

Chlorination of phenylallene derivatives with 1-chloro-1,2-benziodoxol-3-one: synthesis of vicinal-dichlorides and chlorodienes

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