2-Methyl-naphthalene photolysis

Laser flash photolysis techniques offer the possibility of examining in detail the transient processes responsible for the photostabilizing effect discussed above. The triplet lifetimes are frequently too short, even for this technique however, they can still be estimated using as a probe the quenching by 1-methyl-naphthalene, which leads to the formation of its easily detectable triplet. The optical absorbance due to the 1-methylnaphthalene triplet (Aft) produced as a result of energy transfer is related to the Stern-Volmer slope by equation 5, where N stands for... 

As described previously, (4-benzoylphenoxy)methylnaphthalene exhibited C—O bond dissociation via the T state. The multiple laser excitation technique allows us to study stepwise cleavage of two equivalent bonds in a molecule. To provide clear evidence for the stepwise photocleavage of two equivalent bonds in a molecule, we introduce here two C—O bond cleavages of l,8-bis[ (4-benzoylphenoxy)methyl]naphthalene (l,8-(BPO-CH2)2Np) to give acenaph-thene with the three-step excitation using three-color three-laser flash photolysis (Scheme 2.14) [147],... 

Ouchi, A. and Adam, W, Laser-jet photolysis of l,8-bis(substituted-methyl)naphthalenes the effect of heteroatom leaving groups on the two-photon C-C bond formation, /. Chem. Soc., Chem. Commun., 628-629, 1993. 

Ouchi, A. and Koga, Y, Time-delayed, two-color excimer laser photolysis of l,8-bis(substituted-methyl)naphthalenes with Group 16 atom leaving groups. Tetrahedron Lett., 36, 8999-9002,1995. 

Photolytic. Based on data for structurally similar compounds, acenaphthylene may undergo photolysis to yield quinones (U.S. EPA, 1985). In a toluene solution, irradiation of acenaphthylene at various temperatures and concentrations all resulted in the formation of dimers. In water, ozonation products included 1,8-naphthalene dialdehyde, 1,8-naphthalene anhydride, 1,2-epoxyacenaphthylene, and 1-naphthoic acid. In methanol, ozonation products included 1,8-naphthalene dialdehyde, 1,8-naphthalene anhydride, methyl 8-formyl-1-naphthoate, and dimethoxyacetal 1,8-naphthalene dialdehyde (Chen et al., 1979). Acenaphthylene reacts with photochemically produced OH radicals and ozone in the atmosphere. The rate constants and corresponding half-life for the vapor-phase reaction of acenaphthylene with OH radicals (500,000/cm ) at 25 °C are 8.44 x lO " cmVmolecule-sec and 5 h, respectively. The rate constants and corresponding half-life for the vapor-phase reaction of acenaphthylene with ozone at 25 °C are... 

Photolysis of 5-methyl-1,4-naphthoquinone (24) gives 4-hydroxy-5-methyli-dene naphthalen-1 (5//)-one (25) in the ground state within 2 ps of excitation, with a quantum yield of 1.0.59 Formally, this is a photoenolization reaction however, the product of the reaction also has quinone methide functionality,... 

Methyl-1-phenylcyclopropane (1) was obtained in 33% yield when phenylcyclopropane in tetrahydrofuran was reacted with trimethylsilylmethylpotassium and then with iodo-methane. Photon-induced hydrogen abstraction promoted formation of 7b-phenyl-la,7b-di-hydro-l/f-cyclopropa[a]naphthalen-3(2/f)-one (2) from photolysis of /ra v-l-phenyl-2-(2-oxo-... 

Thermolysis of 3-(3-methyl-2,3-diphenylcycloprop-l -enyl)-l, 2-diphenyl-3-methylcyclo-propene gave diphenylacetylenc and an enyne, either by a direct cycloreversion or through a diradical fragmentation. In contrast, photolysis leads to rearrangement to a naphthalene derivative (see Section 3.3.1.1.). 

Siegel and Judeikis [124] have shown that the photodegradation of polydimethylsiloxane is sensitized by naphthalene. A stepwise biphotonic absorption process, involving the first triplet state of naphthalene as an intermediate, followed by energy transfer, has been proposed. It seems that the decomposition of the polymer occurs via Si—CH3 bond rupture and abstraction of hydrogen atoms by the methyl radicals to produce —Si—CHj radicals. Breaking of the — Si—CH3 bond has also been proposed as the most probable reaction in the vacuum ultraviolet photolysis of polydimethylsiloxane at 123.6 and 147 nm [125]. 

The formation of the benzyl radical by photolysis of toluene in benzene at 4.2 and 77 K has been investigated as a function of light intensity and shown to be unimolecular and biphotonic, and to occur via the lowest excited triplet state. The gas-phase photodissociation of [2,2]paracyclophane (71) into two molecules of /7-quinodimethane and analogous dissociations of two methyl-substituted derivatives have been shown to be efficient two-photon processes.A hot molecule formed by internal conversion from the initially formed singlet electronic excited state is proposed as an intermediate, a mechanism which is completely different from that of the two-photon dissociation of (71) in low-temperature matrices, which involves a triplet state. The photolyses of [2,2]para-cylcophane and [2,2]paracyclophane-l-ene have also been studied in THF and hexane matrices at 77 K, using detection by both luminescence and absorption spectroscopy. The products from both these compounds in THF matrices included alkyl derivatives of rra/15-stilbene, and in hexane matrices alkylphenan-threnes. Cycloreversion of so-called cyclodimers of naphthalene derivatives with benzene or furan, e.g. (72), occurs efficiently upon UV irradiation. ... 

The gas-phase reactions of PAHs with OH and NO3 radicals generated in situ via photolysis of methyl nitrite were followed by ESI-MS. Naphthalene and dg-labeled naphthalene were used as PAH components [443]. 

Photochemical Reactions.—Three-membered Rings. The importance of charge transfer to naphthalene from 1,2-diarylcyclopropanes in their naphthalene-sensitized isomerization has been discussed and an attempt has been made to influence the decay modes of 1,2-diphenylcyclopropane excited states using optically active solvents. Naphthalene-sensitized photolysis of cis-1,2-diphenylcyclopropane in optically active methyl ethers led in all cases to the racemic trans-isomer, but with acetone sensitization slight differences in the photostationary state in different solvents were observed, leading to different cisftrans ratios. ... 

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