Naphthalene sensitization

Examples of intramolecular trapping of carbonyl ylide dipoles by alkenes have now been reported.These include, for example, the conversion of the oxirane (172) into the tetrahydrofuran (173). Carbonyl ylides have also been prepared by irradiation of 2,3-bis-(p-methoxyphenyl)oxirane in the presence of dicyanoanthracene as electron-transfer sensitizer direct or triplet-sensitized irradiation, however, leads mainly to rearrangement via carbon-oxygen bond cleavage. In contrast, cyclohexene oxide and styrene oxide, on naphthalene-sensitized irradiation in alcohols, undergo solvolysis via oxide anion-radical intermediates. ... 

Dektar and Hacker have studied the sensitized photolysis of sulfonium salts extensively [70,83]. Like diphenyliodonium cation, triphenylsulfonium is reduced by anthracene singlet to triphenylsulfur radical which cleaves incage to yield phenyl radical and diphenylsulfide [91]. Naphthalene sensitized photolysis of triarylsulfonium salts yielded some of the same photoproducts observed in direct photolysis, namely arylated diarylsulfides [94a] ... 

Figure 7 Stern-Volmer plots of (a) the naphthalene-sensitized reaction of endo-dicyclopentadiene (O) and (b) the fluorescence of naphthalene in the presence of benzene ( )...

The naphthalene-sensitized isomerization of 1,2-diarylcyclopropanes has been the subject of several investigations during the past few years. The most recent study has examined the isomerization of c/s-l, 2-diphenylcyclopropane sensitized... 

Hammond, Mislow, and coworkers extended their work to alkyl tolyl sulfoxides, particularly with naphthalene sensitization, both inter- and intramolecular [74-76]. In general, direct irradiation caused substantially more decomposition than the sensitized cases. In the sensitized case, correlation was made... 

Pandey and colleagues reported the intramolecular photocycliza-tion of 6-halo terminal alkenes using organosilicon compounds having Si-Se bond as shown in Scheme 13." The 1,5-dimethoxy-naphthalene-sensitized photoreaction generates RjSi and PhSe" by the dissociation of the radical anion of PhSe-SiRj. Key intermediates in this complex system are RjSi and PhSe. The former radical abstracts a halogen atom and the latter radical is trapped by a terminal radical giving a cyclopentane derivative. 

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. ... 

Tetrahydronaphthalene is produced by the catalytic treatment of naphthalene with hydrogen. Various processes have been used, eg, vapor-phase reactions at 101.3 kPa (1 atm) as well as higher pressure Hquid-phase hydrogenation where the conditions are dependent upon the particular catalyst used. Nickel or modified nickel catalysts generally are used commercially however, they are sensitive to sulfur, and only naphthalene that has very low sulfur levels can be used. Thus many naphthalene producers purify their product to remove the thionaphthene, which is the principal sulfur compound present. Sodium treatment and catalytic hydrodesulfuri2ation processes have been used for the removal of sulfur from naphthalene the latter treatment is preferred because of the ha2ardous nature of sodium treatment. 

The above generalities apply particularly to palladium. Hydrogenation over platinum or rhodium are far less sensitive to the influence of steric crowding. Reduction of 1-t-butylnaphthalene over platinum, rhodium, and palladium resulted in values of /ci//c2 of 0.42, 0.71, and 0.024, respectively. Also, unlike mononuclear aromatics, palladium reduces substituted naphthalenes at substantially higher rates than does either platinum or rhodium. For example, the rate constants, k x 10 in mol sec" g catalyst", in acetic acid at 50 C and 1 atm, were (for 1,8-diisopropylnaphthalene) Pd (142), Pt(l8.4), and Rh(7.1)(25). 

Dinitro-1-Naphthol (2,4-Dinitro-l-oxy-naphthalene). Yellow crysts, mp 139.5°. Sol in ale chlf. Prepn from naphthalene as a byproduct during nitration with dil nitric acid Hg(II) nitrate. The Lead Salt of the above can be shown as Pb[O.C loHs(N02)2]2, mw 729.57, N 7.68%, OB to C02 -76.75%. The explosive sensitivity of this salt compared to PA is 49%... 

An excellent discussion on derivatization techniques has been given by Lawrence (17) including a detailed discussion on pre-column derivatization (18) and post-column derivatization (19). Probably, the more popular procedures are those that produce fluorescing derivatives to improve detector sensitivity. One of the more commonly used reagents is dansyl chloride (20), 5-dimethylamino-naphthalene-1-sulphonyl chloride (sometimes called DNS-chloride or DNS-C1). The reagent reacts with phenols and primary and secondary amines under slightly basic conditions forming sulphonate esters or sulphonamides. 

Quinone-mono-ketals 46 and 47 are also low reactive dienophiles and are sensitive to Lewis-acid catalysts. The use of high pressure overcomes this limitation [17]. As shown in Equation 5.7, cycloadditions with a variety of substituted 1,3-butadienes 48 occur regioselectively and c This approach provides access to a variety of annulated benzenes and naphthalenes after aromatization of adducts 49. 

The initial discoveries of the extension of the aromatic ring of the ortho-phthalaldehyde (OPA) to a naphthalene-2,3-dicarboxaldehyde (NBA) and the substitution of cyanide (CN ) for 2-ME as the nucleophile have provided the Center with a much more versatile reagent system (5,11), which maintains the sensitivity for primary aliphatic amines and amino acids, and now is known to form fluorescent products with oligopeptides, proteins, and other related analytes that possess a primary amine function (Equation 1). 

J. M. H. King, P. M. Digrazia, B. Applegate, R. Burlage, J. Sanseverino, P. Dunbar, F. Larimer, and G. S. Sayler, Rapid, sensitive bioluminescent reporter technology for naphthalene, exposure and biodegradation. Science 249 11% (1990). 

This reaction is sensitized with acetophenone and quenched by naphthalene, di-f-butylnitroxide, or piperylene. 

As with 2-cyclopentenone, the ratio (70) (71) varies with the molar concentration of the enone, the head-to-head dimer (71) becoming increasingly important at higher concentrations/133 This reaction is efficiently sensitized by acetophenone, benzophenone, thioxanthone, and naphthalene. The same enone concentration effect was observed in the sensitized photo-dimerization as in the direct photolysis. Similarly, quenching of the dimerization by piperylene was not accompanied by a change in dimer ratio. Systematic... 

In the case of /3-styryInaphthalene, direct or sensitized excitation apparently does not involve exclusive formation of a single excited state from the two isomers.(S4) This seems reasonable in that the naphthalene and styryl moieties can act as coupled low-energy chromophores. 

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