Naphthalene energy

Figure 32. Potential energy distribution for the naphthalene dianion electrostatic attraction between a positive point charge and the naphthalene anion where the positive charge is 3 A above the nuclear plane of naphthalene. Energy in units of f3°00 (100).

Conformationally rigid cis-2,3-dihydroindan-l-ones have been prepared " and intramolecular energy transfer in these systems has been studied. For (395), for example, irradiation in the Lj, band and the n-n transition showed neither fluores-ence from naphthalene nor phosphoresence from indanone, but only phosphoresence from naphthalene. Energy-transfer and energy-wasting processes are discussed in relation to the configurations of the molecules. 

A good example is the spectnun of naphthalene. The two lowest excited states have 62 and synnnetries and are allowed for one-photon transitions. A weak transition to one of these is observable in die two-photon spectnun [33], presumably made allowed by vibronic effects. Much stronger two-photon transitions are observable at somewhat higher energies to a and an A state lying quite close to the energies predicted by theory many years earlier [34]. 

Figure Bl.16.14. Top, the canonical axes for triplet naphthalene. The z-axis is directed out of the plane of the paper. Bottom, energy levels and relative populations during the CIDEP triplet mechanism process. See text...

The preferred route to higher purity naphthalene, either coal-tar or petroleum, is crystallisation. This process has demonstrated significant energy cost savings and yield improvements. There are several commercial processes available Sulser-MWB, Brodie type. Bets, and Recochem (37). 

Approximately 45% of the world s phthaUc anhydride production is by partial oxidation of 0-xylene or naphthalene ia tubular fixed-bed reactors. Approximately 15,000 tubes of 25-mm dia would be used ia a 31,000 t/yr reactor. Nitrate salts at 375—410°C are circulated from steam generators to maintain reaction temperatures. The resultant steam can be used for gas compression and distillation as one step ia reduciag process energy requirements (100). 

Benzene rings can also be fused in angular fashion, as in phenanthrene, chrysene, and picene. These compounds, while reactive toward additions in the center ring, retain most of the resonance energy per electron (REPE) stabilization of benzene and naphthalene. ... 

Scheme 9.S. Stabilization Energies and Index of Aromaticity for Heteroaromatic Structures Isoelectronic with Benzene or Naphthalene "...

The polycyclic aromatic hydrocarbons such as naphthalene, anthracene, and phenan-threne undergo electrophilic aromatic substitution and are generally more reactive than benzene. One reason is that the activation energy for formation of the c-complex is lower than for benzene because more of the initial resonance stabilization is retained in intermediates that have a fused benzene ring. 

CNDO calculations provide estimates of the localization energies. For benzene, naphthalene, and anthracene, these are, respectively, 36.3, 15.4, and 8.3 kcal/mol. ... 

Draw Lewis structures (or a series of Lewis structures) for the intermediate ions formed by addition of N02 to naphthalene at the 1 and 2 positions (nitro-naphthalenium ions ). On this basis, are you able to anticipate which intermediate is likely to be the more stable Examine the energies of 1-nitronaphthalenium and 2-nitronaphthalenium ions to see which ion is actually more stable. Which substitution product should be favored Is this the same product anticipated by inspection of naphthalene s HOMO Is it the observed product ... 

Line No. Naphthalene substituents Nucleophile (solvent) Unimolecular rate constant (temp. °C) 10 A ,sec i Activation energy kcal mole-1 Frequency factor logioA Ref. 

Naphthalene and other polycyclic aromatic hydrocarbons show many of the chemical properties associated with aromaticity. Thus, measurement of its heat of hydrogenation shows an aromatic stabilization energy of approximately 250 kj/mol (60 kcal/mol). Furthermore, naphthalene reacts slowly with electrophiles such as Br2 to give substitution products rather than double-bond addition products. 

Let us discuss now the conditions required for the electron transfer process. This reaction requires, of course, a suitable electron donor (a species characterized by a low ionization potential) and a proper electron acceptor, e.g., a monomer characterized by a high electron affinity. Furthermore, the nature of the solvent is often critical for such a reaction. The solvation energy of ions contributes substantially to the heat of reaction, hence the reaction might occur in a strong solvating solvent, but its course may be reversed in a poorly solvating medium. A good example of this behavior is provided by the reaction Na -f- naphthalene -> Na+ + naphthalene". This reaction proceeds rapidly in tetrahydrofuran or in dimethoxy... 

The Nature of the Chemical Bond. V. The Quantum-Mechanical Calculation of the Resonance Energy of Benzene and Naphthalene and the Hydrocarbon... 

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