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Naphthalene carbon atom reactivity

Diphenylmethane Base Method. In this method, the central carbon atom is derived from formaldehyde, which condenses with two moles of an arylamine to give a substituted diphenylmethane derivative. The methane base is oxidized with lead dioxide or manganese dioxide to the benzhydrol derivative. The reactive hydrols condense fairly easily with arylamines, sulfonated arylamines, and sulfonated naphthalenes. The resulting leuco base is oxidized in the presence of acid (Fig. 4). [Pg.272]

Naphthalene intermediates [61] are always built up by substitution reactions starting from the cheap and plentiful hydrocarbon using, in the main, only seven basic reactions. Most of these reactions are generally familiar from benzene chemistry but with some modification, since naphthalene has two different possible positions of substitution. These positions are often designated a and [3, the four a-positions being ortho and the four P-positions meta to the nearest carbon atom of the central bond. A further modifying influence is the lower level of aromaticity of naphthalene compared with benzene, leading to increased reactivity. [Pg.196]

A very reactive nitrogen atom is required to convert benzenes or naphthalenes into pyridines, and there are a number of such reactions which involve nitrenes or nitrenoid species. A number of substituted benzenes have been treated with sulfonyl diazide or carbonyl diazide and moderate yields of pyridines recorded (27CB1717). Thus p-xylene gives 2,5-dimethylpyridine there is no indication of the fate of the carbon atom which is lost. More controlled reaction is possible in intramolecular insertions. The examples in which o-nitrotoluene is converted into a derivative (759) of 2-acetylpyridine, and where 2,3-diazidonaphthalenes give 3-cyanoisoquinolines (760) are quoted in a review (81 AHC(28)231>. [Pg.498]

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. [Pg.306]

The reader may, however, object that there are a number of molecules, the alternant hydrocarbons which we discussed in great detail in Chapter Six, in which the charge densities, q at all carbon atoms, r, (r = 1,2,..., ) are identically unity, by part 3 of the Coulson-Rushbrooke theorem. Examining the 7r-electron charge at the various sites in such a molecule is, therefore, no longer a way of distinguishing one position from another. For example, is the a-position in naphthalene more reactive than the -position, and, if so, why Such a distinction cannot depend upon the qr, for, as we have just observed, they are all equal. In that case we shall just have to make appeal to the next-highest-order differential—a procedure which introduces a new set of properties, called polarisabilities, which have proved quite important in the study of this kind of system. The word polarisability is rather an unfortunate one, but we shall use it and deal here with so-called atom-atom polarisabilities . [Pg.73]

The amplitude of the frontier orbitals determines the selectivity. The most reactive atom in a molecule has the largest amplitude of the frontier orbitals. The frontier orbitals overlap each other to the greatest extent at the sites with the largest amphtudes. Reactions occur on the atoms in the electron donors and acceptors, where the HOMO and LUMO amplitudes are largest, respectively. Electrophiles prefer the a position of naphthalene, an electron donor, with the larger HOMO amplitude (Scheme 21). Nucleophiles attack the carbons of the carbonyl groups, an electron acceptor, with the larger LUMO amplitude (Scheme 7). [Pg.17]

Jerry Dias, a chemist at the University of Missouri—Kansas City, has devised a periodic classification of a class of organic molecules called benzenoid aromatic hydrocarbons, of which naphthalene, Cj Hg, is the simplest example (figure 1.10). By analogy with Johann Dobereiner s triads of elements, described in chapter 2, these molecules can be sorted into groups of three in which the central molecule has a total number of carbon and hydrogen atoms that is the mean of the flanking entries, both downward and across the table. This periodic scheme has been apphed to making a systematic study of the properties of benzenoid aromatic hydrocarbons, which has led to the predictions of the stabihty and reactivity of many of their isomers. [Pg.25]


See other pages where Naphthalene carbon atom reactivity is mentioned: [Pg.82]    [Pg.200]    [Pg.535]    [Pg.535]    [Pg.16]    [Pg.3271]    [Pg.2937]    [Pg.352]    [Pg.966]    [Pg.621]    [Pg.174]    [Pg.477]    [Pg.559]    [Pg.182]    [Pg.722]    [Pg.21]    [Pg.106]    [Pg.43]    [Pg.26]    [Pg.238]    [Pg.285]    [Pg.232]   
See also in sourсe #XX -- [ Pg.475 , Pg.483 ]




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