NAPHTHALENE AND DERIVATIVES

Naphthalene as such has several important uses. Its most common use is as a germicide or insecticide against the attacks of the moth miller larvae in the form of what is known as moth-balls. A more important use is as an enricher or carburetter of water gas for illuminating purposes. As it contains a large amount of carbon it burns with a very luminous flame and thus makes more luminous a weakly illuminating gas. The most important uses of all, however, are as a source of ortho-phthalic acid and in yielding derivatives which are used as dyes. 

Constitution.—The composition of naphthalene is represented by the formula CioHg. What is its constitution In the first place it is a hydrocarbon similar in its chemical properties to benzene and not to methane. It readily forms nitro and sulphonic acid derivatives and its hydroxyl derivatives are analogom to phenols, not to alcohols. It also yields hydrogen and halogen addition products like benzene. The true constitution of the compound has been established by reactions both of decomposition and of synthesis. 

Yields ortho-Phthalic Acid.—The simplest proof that naphthalene does contain a benzene ring is found in the fact that on oxidation it yields phthalic acid and always the ortho compound. This would indicate 

The easy oxidation of such unsaturated side chains would be expected fp. 670). 

Phenyl butylene bromide i-2-Di-brom 4-phenyl butane 

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Other important expls obtd on nitration of products of distillation of coal tar were Di- and Tri nitrobenzene (Vol 2 of Encycl, pp B46ff and Nitronaphthalenes, which will be described under Naphthalene and Derivatives... 

Naphthalene and Derivatives. The time-temperature relationship is especially important in this series from the standpdnt of isomer distribution. Low temperatures (SO C and below) and/or diort reaction periods favor alpha substitution, while higher tena(peratures (about 160 C) and/or a longer time favor beta substitution. Even when the more stable beta isomer is the final product, the less stable (but more easily formed) alpha isomer is produced first, but imdergoes desulfonation and resulfonatimi to the beta sulfonate. The data for naphth ene are shown in Table 7-11. The same considerations hold in the disulfonation of naphthalene and in the preparation of the naphthd- and naphthylaminesuHonic acids. 

The sequential nucleophile/electrophile addition can also be applied to the dearomatization of naphthalene and derivatives. Treatment of [Cr(CO)3(l,4-dimethoxynaphthalene)] with 2-methyl-2-litihiodithiane affords a single regio-isomeric dihydronaphthalene (Scheme 24) [35, 40]. In the second example in Scheme 26, an a-nitrile anion is used. HMPA is essential in this case to favor alkylation of the metal as opposed to anion dissociation [40]. 

Figure 16.13 presents the studies of Rehm and Weller [29] of the quenching of fluorescence of naphthalene and derivatives by amines in acetonitrile solution for the range of... 

Fused Systems.—Naphthalene and Derivatives. A new method of aromatization of partially hydrogenated aromatic hydrocarbons overcomes the difficulty of the competing Diels-Alder reaction of reactive arenes. The method is based on deprotonation-hydride elimination in which potassium fencholate (277) serves as the base and fenchone (278) as the hydride acceptor, catalytic amounts only of fencholate being required since it is regenerated in the aromatisation step. In this way, the conversion of 1,2-dihydronaphthalene into naphthalene and of 9,10-dihydroanthracene into anthracene proceeds almost quantitatively. 

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