Example Naphthalene Results

As an illustration of the performance of TDDFT, we compare various density functionals and wave function methods for the first singlet excited states of naphthalene in Tables 4, 5, and 6. All calculations were performed using the aug-TZVP basis set, while the complete active space self-consistent field (SCF) with second-order perturbation theory (CASPT2) results from Ref. 200 were obtained in a smaller double-zeta valence basis set with some diffuse augmentation. The experimental results correspond to band maxima from gas-phase experiments however, the position of the band maximum does not necessarily coincide with the vertical excitation energy, especially if 

The use of hybrid functionals leads to systematically higher excitation energies. On average, this is an improvement over the GGA results, which are systematically too low. However, while diffuse excitations benefit from mixing in some exact exchange due to a reduction of the self-interaction error, valence excitation energies are not always improved, as is obvious for the and valence states. 

The state is erroneously predicted below the state by all density functionals in Table 4, which is a potentially serious problem for applications in photochemistry. This is not corrected by hybrid mixing. 

The l Bzu excitation is polarized along the short axis of the naphthalene molecule. In Platt s nomenclature of excited states of polycyclic aromatic hydrocarbons (PAHs), l Bzu corresponds to the La state, which has more ionic character than the 1 B3 (or Lj,) state. Parac and Grimme have pointed 

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In alternant hydrocarbons (p. 55), the reactivity at a given position is similar for electrophilic, nucleophilic, and free-radical substitution, because the same kind of resonance can be shown in all three types of intermediate (cf. 20,22, and 23). Attack at the position that will best delocalize a positive charge will also best delocalize a negative charge or an unpaired electron. Most results are in accord with these predictions. For example, naphthalene is attacked primarily at the 1 position by NOj, NHJ, and Ph, and always more readily than benzene. 

There is neither a partial positive nor a partial negative charge on the two nonequivalent positions 1 and 2 of naphthalene, which are poised for electrophilic substitution. One might consequently predict that electrophiles react with naphthalene without regiocontrol. Furthermore, this should occur with the same reaction rate with which benzene reacts. Both predictions contradict the experimental results For example, naphthalene is brominated with a 99 1 selectivity in the 1-position in comparison to the 2-position. The bromination at Cl takes place 12,000 times faster and the bromination at C2 120 times faster than the bromination of benzene. 

The pyrolytic studies on meteorites are commonly done at different temperatures. A preheating step is utilized to insure that any possible adsorbed gases on the surface of the meteorite from the terrestrial environment are eliminated. Several organic compounds are monitored in pyrolysates such as polycyclic aromatic compounds. As an example, the results on naphthalene production upon pyrolysis from several carbonaceous chondrites, normalized by the total carbon content before pyrolysis, are shown in Figure 17.2.1 [76],... 

As implied by the above treatment, the conversion of A into A7, Met+ is never quantitative. For example, reduction of naphthalene in tetrahydrofaran by sodium yields about 95% of its radical anions at ambient temperature, whereas the yield in diethyl ether is very low, less than 1%. The sodium reduction of biphenyl, a hydrocarbon of lower electron affinity than naphthalene, results only in about 20% conversion in tetrahydrofaran, although nearly 100% reduction may be accomplished in dimethoxy-ethane. Since these processes lead to equilibria, it is immaterial whether they take place on the surface of the metal, being followed by desorption of the product, or whether they proceed homogeneously in a solution saturated by metal atoms and their ionization products, these being replenished from the bulk of the solid metal as the reduction proceeds. 

Occasionally, unusual effects are observed. For example, addition of styrene to living poly-vinyl-naphthalene results in complexing of the first polystyryl-anion to the preceding naphthalene moiety501. Consequently, three constants describe the process the rate constant of addition of the first styrene molecule, the very low rate constant of addition of the second styrene molecule, and a large rate constant of homo-propagation ensuing from addition of the third, forth, etc., styrene molecules. 

As an example of the use of these formulae we choose naphthalene (Figure 4.3c) for which, using the axis notation in which the short in-plane axis is the z axis and the long inplane axis the y axis, niy = 4, m2 = 1 and all other m are zero. This gives the result that the 48 normal vibrations are distributed as follows 9a, 4a , 3 1, t>2g, 8h2 , 8 3g. 4h3 . 

The relative stability of the intermediates determines the position of substitution under kinetically controlled conditions. For naphthalene, the preferred site for electrophilic attack is the 1-position. Two factors can result in substitution at the 2-position. If the electrophile is very bulky, the hydrogen on the adjacent ring may cause a steric preference for attack at C-2. Under conditions of reversible substitution, where relative thermodynamic stability is the controlling factor, 2-substitution is frequently preferred. An example of this behavior is in sulfonation, where low-temperature reaction gives the 1-isomer but at elevated temperatures the 2-isomer is formed. ... 

Example.—Using the same solvent and adding successively three lots of substance (naphthalene), the following results were obtained —... 

Meyers has demonstrated that chiral oxazolines derived from valine or rert-leucine are also effective auxiliaries for asymmetric additions to naphthalene. These chiral oxazolines (39 and 40) are more readily available than the methoxymethyl substituted compounds (3) described above but provide comparable yields and stereoselectivities in the tandem alkylation reactions. For example, addition of -butyllithium to naphthyl oxazoline 39 followed by treatment of the resulting anion with iodomethane afforded 41 in 99% yield as a 99 1 mixture of diastereomers. The identical transformation of valine derived substrate 40 led to a 97% yield of 42 with 94% de. As described above, sequential treatment of the oxazoline products 41 and 42 with MeOTf, NaBKi and aqueous oxalic acid afforded aldehydes 43 in > 98% ee and 90% ee, respectively. These experiments demonstrate that a chelating (methoxymethyl) group is not necessary for reactions to proceed with high asymmetric induction. 

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). 

Rather similar was the paper [PolG36a] which also derives asymptotic formulae for the number of several kinds of chemical compounds, for example the alcohols and benzene and naphthalene derivatives. Unlike the paper previously mentioned, this one gives proofs of the recursion formulae from which the asymptotic results are derived. A third paper on this topic [PolG36] covers the same sort of ground but ranges more broadly over the chemical compounds. Derivatives of anthracene, pyrene, phenanthrene, and thiophene are considered as well as primary, secondary, and tertiary alcohols, esters, and ketones. In this paper Polya addresses the question of enumerating stereoisomers -- a topic to which we shall return later. 

Experiments using marine sediment slurries have examined the effect of pre-exposure to various aromatic hydrocarbons on the rate of subsequent degradation of the same, or other hydrocarbons. The results clearly illustrated the complexity of the selection process for example, whereas pre-exposure to benzene, naphthalene, anthracene, or phenanthrene... 

Nitration can be catalyzed by lanthanide salts. For example, the nitration of benzene, toluene, and naphthalene by aqueous nitric acid proceeds in good yield in the presence of Yb(03SCF3)3.5 The catalysis presumably results from an oxyphilic interaction of nitrate ion with the cation, which generates or transfers the N02+ ion.6 This catalytic procedure uses a stoichiometric amount of nitric acid and avoids the excess strong acidity associated with conventional nitration conditions. 

This silylene formation from 27 under mild conditions permits the synthesis of a variety of interesting carbo- and heterocycles, most of which are new types of compounds. The results are summarized in Schemes 5 and 6. The reactions with benzene and naphthalene represent the first examples of [2+1] cycloadditions of a silylene with aromatic C=C double bonds.59 623 The reactions with carbon disulfide and isocyanide (Scheme 6) are also of great interest because of their unusual reaction patterns.62b... 

Just as in NMR, a multiplet pattern gives an important clue to the identity of a radical. For example, in the naphthalene anion radical, there are four a (positions 1, 4, 5, 8) and four p protons (positions 2, 3, 6, 7). Each proton splits the electronic energy levels in two. Since the a protons are equivalent, for example, the splitting is the same for each proton. Thus, as shown on the right side of Figure 2.1, five equally spaced energy level values result. 

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