Carbonium ions naphthalene

The HO—LU interaction came early to the notice of theoreticians. Hiickel 74> pointed out the role of LU in the alkaline reduction of naphthalene and anthracene. Moffitt 75> characterized the formation of S03, SO2CI2, etc. by the reactions of SO2 as an electron donor with the S-atom-localiz-ing character of HO MO. Walsh 76) considered that the empirical result of producing nitro compounds in the reaction of the nitrite anion with the carbonium ion should be attributed to the HO of the NO2 anion which is localized at the nitrogen atom. 

The authors carried out the calculation for a considerable number of aromatic hydrocarbons by this method, in part also including configuration interaction (01). As in the case of anthracene, the possibility of isomeric carbonium ions was taken into account for biphenyl, naphthalene, phenanthrene, pyrene, and perylene. Comparison with the measured spectra permitted a distinction between the isomeric carbonium ions in some cases. The possibility of this differentiation only... 

Neither C5- nor C6-cyclization involve carbonium-ion intermediates over platinum metal. The rates of the -propylbenzene - indan reaction (where the new bond is formed between a primary carbon atom and the aromatic ring) and the n-butylbenzene- 1-methylindan reaction (which involves a secondary carbon atom) are quite similar (13). Furthermore, comparison of the C6-cyclization rates of -butylbenzene and n-pentylbenzene (forming naphthalene and methylnaphthalene, respectively) over platinum-on-silica catalyst shows that in this reaction a primary carbon has higher reactivity than a secondary carbon (Table IV) (29). Lester postulated that platinum acts as a weak Lewis acid for adsorbed cyclopentenes, creating electron-deficient species that can rearrange like carbonium ions (55). The relative cyclization rates discussed above strongly contradict Lester s cyclization mechanism for platinum metal. 

Carbonium ions produced from the decay of solid tritiated molecules Recently, the reactions initiated by the -decay of solid naphthalene- -t were studied by a technique based on electron paramagnetic resonance (Lloyd etal., 1968). A polycrystalline sample, stored at 77°K, developed an e.s.r. spectrum ascribed to the 1-naphthyl radical, which changed rapidly on warming to room temperature into the nine-line spectrum of the 1-hydronaphthyl radical ... 

Like benzene, naphthalene typically undergoes electrophilic substitution this is one of the properties that entitle it to the designation of aromatic. An electrophilic reagent finds the ir cloud a source of available electrons, and attaches itself to the ring to form an intermediate carbonium ion to restore the stable aromatic system, the carbonium ion then gives up a proton. 

In our study of electrophilic substitution in the benzene ring (Chap. II), we found that we could account for the observed orientation on the following basis (a) the controlling step is the attachment of an electrophilic reagent to the aromatic ring to form an intermediate carbonium ion and (b) this attachment takes plaqe in such a way as to yield the most stable intermediate carbonium ion. Let us see if this approach can be applied to the nitration of naphthalene. 

Attack by nitronium ion at the a-position of naphthalene yields an intermediate carbonium ion that is a hybrid of structures I and II in which the positive charge is accommodated by the ring under attack, and several structures like III in which the charge is accommodated by the other ring. 

We have seen (Sec. 30.9) that orientation in naphthalene can be accounted for on the same basis as orientation in substituted benzenes formation of the more stable intermediate carbonium ion. In judging the relative stabilities of these naphthalene carbonium ions, we have considered that those in which an aromatic sextet is preserved are by far the more stable and hence the more important. Let us see if we can account for orientation in substituted naphthalenes in the same way. 

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