Naphthalene, Electrochemical Oxidation reactions

While such a device has yet to be constructed, Debreczeny and co-workers have synthesized and studied a linear D-A, -A2 triad suitable for implementation in such a device.11641 In this system, compound 6, a 4-aminonaphthalene monoimide (AN I) electron donor is excited selectively with 400 nm laser pulses. Electron transfer from the excited state of ANI to Ai, naphthalene-1,8 4,5-diimide (NI), occurs across a 2,5-dimethylphenyl bridge with x = 420 ps and a quantum yield of 0.95. The dynamics of charge separation and recombination in these systems have been well characterized.11651 Spontaneous charge shift to A2, pyromellitimide (PI), is thermodynamically uphill and does not occur. The mechanism for switching makes use of the large absorption cross-section of the NI- anion radical at 480 nm, (e = 28,300). A second laser pulse at 480 nm can selectively excite this chromophore and provide the necessary energy to move the electron from NI- to PI. These systems do not rely on electrochemical oxidation-reduction reactions at an electrode. Thus, switching occurs on a subpicosecond time scale. 

Tautomeric trifluoromethyl-substituted spirocyclic quinazolines 693 and 694 were formed when p-benzoquinone imines 692 (synthesized by electrochemical oxidation of the corresponding p-anisidine derivatives 691) were heated in DMSO at 120 °C (Scheme 145) [409], The reaction was affected by solvent (DMSO giving the highest yields) and nature of the substituents in 692, In the case of naphthalene derivatives (e.g. 695), thecyclization gave single tautomers (e.g. 696). A synchronous mechanism was proposed for this transformation. 

A third important reaction of aromatic radical-cations is carbon-carbon bond formation with a further aromatic substrate. This reaction is limited to the oxidation in acetonitrile of substrates with electrondonating substituents. Radical-cations from benzene, naphthalene and anthracene form a-complexes but do not form a a-bonded reaction intermediate. Tlie dimerization reaction has been investigated both by pulse-radiolysis [22] in water and by electrochemical methods [27] in acetoni-... 

Electrochemistry can also be used to induce aromatic nucleophilic substitutions by setting up the electrode potential at the level, which is appropriate to reduce an aromatic substrate. When this electrochemical process is carried out in the presence of a nucleophilic reagent, the or reactions take place. Indeed, halogenated derivatives of benzophenone, benzonitrile, and naphthalene undergo nucleophilic displacement reactions with thiolates, which are able to occur catalytically [76, 77]. The reaction mechanism involves the formation of the anion radical at the electrode and its further decomposition into a neutral radical, which reacts with a nucleophile, thus yielding the anion-radical of the substitution product. In case of the catalytic reaction, oxidation of the anion-radical species may occur by electron transfer with the substrate and/or the electrode (Scheme 17). 

Nitrite Nitrite is an important indicator of fecal pollution in natural waters as well as a potential precursor of carcinogenic species. A rush of flow and sequential injection spectrophotometric method based on Griess-type reactions has been proposed, also coupled to online sorbent enrichment schemes. The catalytic effect of nitrite on the oxidation of various organic species constitutes the basis of fairly sensitive spectrophotometric methods. Fluorometric methods based on the formation of aromatic azoic acid salts, quenching of Rhodamine 6G fluorescence, and direct reaction with substituted tetramine or naphthalene species have been also reported. Indirect CL methods usually involve conversion into nitric oxide and gas-phase detection as mentioned in the foregoing section. The redox reaction between nitrite and iodide in acidic media is the fundamental of a plethora of flow injection methodologies with spectrophotometric, CL, or biamperometric detection. New electrochemical sensors with chemically modified carbon paste electrodes containing ruthenium sites, or platinum electrodes with cellulose or naphthalene films, have recently attracted special attention for amperometric detection. 

In the following we want, therefore, to describe first the structure of the simplest organic metal derived from as simple molecules as naphthalene or other arenes. These structures help to understand the type of intermolecular interactions necessary to produce a quasi-metallic state in organic systems. The structure and the structural changes upon oxidation ("doping") of poly(acetylene) will then be described. A description of these chemical reactions and their implications for the electronic and vibronic spectra will follow. Finally, some other conducting polymers or oligomers will be described and the use of such materials in electrochemical cells will be discussed as well. 

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