Laser flash photolysis of 1,8-bis(substituted methyl)naphthalenes

Ouchi, Akihiko; Koga, Yoshinori; Alam, Maksudul M.; Ito, Osamu

doi:10.1039/p29960001705

Cited by 10 publications

(15 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This observation is и 1-NaphSe similar to that of [13,27]. The low reactivity to и PhSe O 2 was also reported for the aryloxy and arylthio radicals [15,16]. Thus, the absorption bands in Figure 2 are attributed to (eq.…”

Section: Transient Absorption Spectrasupporting

confidence: 73%

Laser-flash photolysis of naphthyl diselenides; reactivities of naphthylseleno radicals

Alam

Ito

Koga³

et al. 1998

Int. J. Chem. Kinet.

Self Cite

View full text Add to dashboard Cite

Transient absorption spectra of 1-naphthylseleno and 2-naphthyl-и(1-NaphSe ), seleno radicals, which are generated by laser-flash photolysis of the correspond-и (2-NaphSe ) ing diselenides, were observed. The reactions of and with 2-methyl-и и 1-NaphSe , 2-NaphSe 1,3-butadiene and ␣-methylstyrene were investigated by following the decay rates of these seleno radicals. By both steady-state and laser-flash photolysis, it is proved that these seleno radicals add to alkenes in a reversible manner. The reaction rate constants for such reversible addition reactions were determined by conducting the reaction in the presence of O 2 , which traps selectively the carbon-centered radicals formed by the addition reaction of the seleno radicals to the alkenes. The reactivity of is higher than that of both of и и 2-NaphSe 1-NaphSe , which are less reactive than These reactivities were interpreted with the properties of и PhSe . SOMO calculated by MO method.

show abstract

Section: Transient Absorption Spectrasupporting

confidence: 73%

Laser-flash photolysis of naphthyl diselenides; reactivities of naphthylseleno radicals

Alam

Ito

Koga³

et al. 1998

Int. J. Chem. Kinet.

Self Cite

View full text Add to dashboard Cite

show abstract

“…15 Additionally, this hypothesis provides an explanation of why "bad" leaving groups in the ground state, such as hydroxides or alkoxides, can be "good" leaving groups in the excited state, because making a highenergy ion pair would elevate the ground-state surface. 57 In conclusion, we have shown that carbocations favored from photoheterolysis tend to have nearby, low-energy conical intersections, while stable carbocations from thermal heterolysis tend to have high-energy, distant conical intersections. These findings lend support to the idea that conical intersection control leads to the frequent inverted substrate preferences between nonadiabatic photoheterolysis and thermal heterolysis.…”

Section: ■ Discussionmentioning

confidence: 62%

Inverted Substrate Preferences for Photochemical Heterolysis Arise from Conical Intersection Control

2014

View full text Add to dashboard Cite

Heterolytic bond scission is a staple of chemical reactions. While qualitative and quantitative models exist for understanding the thermal heterolysis of carbon-leaving group (C-LG) bonds, no general models connect structure to reactivity for heterolysis in the excited state. CASSCF conical intersection searches were performed to investigate representative systems that undergo photoheterolysis to generate carbocations. Certain classes of unstabilized cations are found to have structurally nearby, low-energy conical intersections, whereas stabilized cations are found to have high-energy, unfavorable conical intersections. The former systems are often favored from photochemical heterolysis, whereas the latter are favored from thermal heterolysis. These results suggest that the frequent inversion of the substrate preferences for nonadiabatic photoheterolysis reactions arises from switching from transition-state control in thermal heterolysis reactions to conical intersection control for photochemical heterolysis reactions. The elevated ground-state surfaces resulting from generating unstabilized or destabilized cations, in conjunction with stabilized excited-state surfaces, can lead to productive conical intersections along the heterolysis reaction coordinate. Disciplines Materials Chemistry | Other Chemistry | Physical Chemistry CommentsReprinted (adapted) with permission from J. Am. Chem. Soc., 2014, 136 (25) ABSTRACT: Heterolytic bond scission is a staple of chemical reactions. While qualitative and quantitative models exist for understanding the thermal heterolysis of carbon−leaving group (C−LG) bonds, no general models connect structure to reactivity for heterolysis in the excited state. CASSCF conical intersection searches were performed to investigate representative systems that undergo photoheterolysis to generate carbocations. Certain classes of unstabilized cations are found to have structurally nearby, low-energy conical intersections, whereas stabilized cations are found to have high-energy, unfavorable conical intersections. The former systems are often favored from photochemical heterolysis, whereas the latter are favored from thermal heterolysis. These results suggest that the frequent inversion of the substrate preferences for nonadiabatic photoheterolysis reactions arises from switching from transition-state control in thermal heterolysis reactions to conical intersection control for photochemical heterolysis reactions. The elevated ground-state surfaces resulting from generating unstabilized or destabilized cations, in conjunction with stabilized excited-state surfaces, can lead to productive conical intersections along the heterolysis reaction coordinate.

show abstract

“…Naphthylmethyl radical (NpCH 2 •) is a typical organic radical, and has been extensively studied. [1][2][3][4][5][6][7] It is well established that NpCH 2 • is produced from photolysis of naphthylmethylhalides through cleavage of the naphthylmethyl-halogen bond. 2,4 Cleavage also occurs in other naphthylmethyl compounds under laser irradiation.…”

Section: Rapid Cleavage Of the Naphthylmethyl-oxygen Bond Of 1and 2-[...mentioning

confidence: 99%

“…It is found that cleavage occurs very quickly from 1-NpCH 2 -SPh and 1-NpCH 2 -SePh in the S 1 states. 5 In contrast, the lowest triplet state (T 1 ) of 1-NpCH 2 -OPh is predominantly generated from laser flash photolysis of 1-NpCH 2 -OPh with excitation at 266 nm, because the energy of the T 1 state is lower than the dissociation energy of the NpCH 2 -OPh bond. Steenken and coworkers also found that C-O bond cleavage occurred in the S 1 state but not in the T 1 state of 1-[(4-benzoylphenoxy)methyl]naphthalene (1-NpCH 2 -OBP).…”

Section: Rapid Cleavage Of the Naphthylmethyl-oxygen Bond Of 1and 2-[...mentioning

confidence: 99%

“…1a) was coincident with that of Np(T 1 ) with a peak at 420 nm as reported previously. 5,7 Because the Np chromophore has no absorption at 355 nm, the first 355 -nm photon is absorbed by the BP chromophore to give BP(S 1 ) from which intersystem crossing occurs to give BP(T 1 ) in a quantum yield of 1.0. 9 Intramolecular triplet energy transfer from BP(T 1 ) to the Np chromophore occurs to give Np(T 1 ) within a laser flash of 5 ns.…”

Section: Rapid Cleavage Of the Naphthylmethyl-oxygen Bond Of 1and 2-[...mentioning

confidence: 99%

See 1 more Smart Citation

Rapid cleavage of the naphthylmethyl–oxygen bond in higher triplet excited states

et al. 2003

Self Cite

View full text Add to dashboard Cite

show abstract

Laser flash photolysis of 1,8-bis(substituted methyl)naphthalenes

Cited by 10 publications

References 30 publications

Laser-flash photolysis of naphthyl diselenides; reactivities of naphthylseleno radicals

Laser-flash photolysis of naphthyl diselenides; reactivities of naphthylseleno radicals

Inverted Substrate Preferences for Photochemical Heterolysis Arise from Conical Intersection Control

Rapid cleavage of the naphthylmethyl–oxygen bond in higher triplet excited states

Contact Info

Product

Resources

About