Naphthalene, resonance energy

The difference, -255kJ/mol, is naphthalene s resonance energy. Naphthalene is less aromatic than benzene because a per-ring resonance energy of j(-255) = -127.5 kJ/mol is smaller in absolute value than that of benzene (-150 kJ/mol). 

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. ... 

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

The values of and can be estimated from their internal consistency to be accurate to about 0.1 v.e., the value of 1.71 v.e. for the resonance energy being accurate to about 0.15 v.e. The quantum mechanical discussion of resonance in benzene and naphthalene is given in the preceding paper.1... 

Data are given in Table IV for heterocyclic compounds. For piperidine there is no difference between E and E, showing that the bond energies used are applicable to saturated heterocyclic molecules. Pyridine and quinoline differ from benzene and naphthalene only by the presence of one N in place of CH and, as expected, the values 1.87 v.e. and 3.01 v.e., respectively, of the resonance energy are equal to within 10 percent to the values for the corresponding hydrocarbons. 

The quantum-mechanical treatment previously applied to benzene, naphthalene, and the hydrocarbon free radicals is used in the calculation of extra resonance energy of conjugation in systems of double bonds, the dihydro-naphthalenes and dihydroanthracenes, phenylethylene, stilbene, isostilbene, triphenylethylene, tetraphenylethyl-... 

The secular equation for phenylethylene, in which a phenyl group is conjugated with a double bond, is the same as for 1,2-dihydro-naphthalene, and leads to the same value for the resonance energy. 

Pauling, L. Wheland, G.W. The Nature of the Chemical Bond. V. The Quantum-Mechanical Calculation of the Resonance Energy of Benzene and Naphthalene and the Hydrocarbon Free Radicals J. Chem. Phys. 1933, 1, 362-374 Errata, ibid, 1934, 2, 482. 

It is interesting that attachment of — ( 2)4— and —CH2CH=CHCH2— to benzene results in nearly the same enthalpy of formation change but it is not obvious how fortuitous this equality is we have reasons for considerable skepticism of its validity68. That formation of naphthalene from benzene is accompanied by a lessened enthalpy of formation increase than that of l,6-methano[10]annulene (yet another name for species 90) from tropilidene would appear to be more of a strain than a resonance derived effect. From Roth, we find the resonance energy increase on going from tropilidene to l,6-methano[10]annulene is 55 kJmol-1 and from benzene to naphthalene the increase is nearly the same, nearly 59 kJmol-1. By contrast, the l,5-methano[10]annulene (99) is less stable by 77 kJmol 1 than the species it appears most naturally to be compared with, namely the isomeric 90. 

Theorem 23 Azulene should be semi-aromatic, having resonance energies intermediate between corresponding decapentaene and naphthalene derivatives. 

One can predict that singlet 1-naphthylnitrene will cyclize more readily than phenylnitrene because the resonance energy per aromatic ring is lower in naphthalene than benzene, but by the same token, 1-naphthylnitrene should cyclize more slowly than vinylnitrene. 

Similarly, the fusion of an aromatic ring to the oxepin-benzene oxide system was found to drive the equilibrium toward extremes in either direction. The calculated resonance energies for oxepins (26), (27) and (28) were 4.81, 78.46 and 81.72 kJ mol-1 respectively (70T4269). These calculated values concur with experimental observations since oxepins (27) and (28) have been synthesized and are relatively stable compounds. The formation of 2-benzoxepin (26) from naphthalene 1,2-oxide would involve a considerable loss in resonance energy to the system and has not been detected spectroscopically (67AG(E)385). 

The resonance energies of fused systems increase as the number of principal canonical forms increases, as predicted by rule 6 (p. 35).75 Thus, for benzene, naphthalene, anthracene, and phenanthrene, for which we can draw, respectively, two, three, four, and five principal canonical forms, the resonance energies are, respectively, 36, 61, 84, and 92 kcal/mol (152, 255, 351, and 385 kJ/mol), calculated from heat-of-combustion data.76 Note that when phenanthrene, which has a total resonance energy of 92 kcal/mol (385 kJ/mol), loses the 9,10 bond by attack of a reagent such as ozone or bromine, two complete benzene rings remain, each with 36 kcal/mol (152 kJ/mol) that would be lost if benzene was similarly attacked. The fact that anthracene undergoes many reactions across the 9,10 positions can... 

These three structures, the most stable valence-bond structures that can be formulated for naphthalene, are seen to have about the same energy and to correspond to about the same molecular configuration. It is to be expected then that they will be combined to represent the normal state of the naphthalene molecule, to which they should contribute about equally. Resonance among these three stable structures should stabilize the molecule to a greater extent than does the Kekul resonance in benzene, involving two equivalent structures it is seen from Table 6-2 that the resonance energy of naphthalene, 75 kcal/mole, is indeed much greater than that of benzene. 

For pyridine, pyrazine, and related six-membered heterocyclic molecules Kekul6 resonance occurs as in benzene, causing the molecules to be planar and stabilizing them by about 40 kcal/mole. The interatomic distances observed in these molecules,106 C—C = 1.40 A, C—N = 1.33 A, and N—N 1.32 A, are compatible with this structure. The resonance energy found for quinoline, 69 kcal/mole, is about the same as that of naphthalene. 

NADPH/ NADP+ ratio 776 Naphthalene, resonance energy 299 Nathans, Daniel 84 Natural killer cells 185 Near attack conformation 485 Near-field scanning microscope 130 Neighboring group assistance in displacement reactions 601, 602 Nekoflavin 783 Nematocyst 427 Nematodes 24, 25 Neocarzinostatin 218,224s Neopterin 803... 

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