Naphthalene ring

Sulfonic acids can come from the sulfonation of oil cuts from white oil production by sulfuric acid treatment. Sodium salts of alkylaromatic sulfonic acids are compounds whose aliphatic chains contain around 20 carbon atoms. The aromatic ring compounds are mixtures of benzene and naphthalene rings. 

The naphthalene ring compounds 405 and 406 are tormed by the inter-molecular reaction of /ti-iodoanisole with diphenylacetylene[280]. 

The coupling constants of ortho ( Jhh = 7 Hz), meta Jhh =1-5 Hz) and para protons CJhh I Hz) in benzene and naphthalene ring systems are especially useful in structure elucidation (Table 2.5). With naphthalene and other condensed (hetero-) aromatics, a knowledge of zig zag coupling = 0.8 Hz) is helpful in deducing substitution patterns. 

Two different all-aromatic crowns have been reported ". In 1975, de Jong, Siegel and Cram reported the synthesis of a tri-binaphthyl system in which each oxygen was bound to a naphthalene ring, but aliphatic bridges were used to join the binaphthyl units. Relatives of this compound are discussed further in Sect. 3.13. The synthesis of this molecule (Structure 17, below) was not simple, but was relatively straightforward. An interesting feature of it was the use of ethyl chloroacetate followed by LAH reduction to attach ethyleneoxy units to the naphthol unit. 

Variable-temperature HNMR spectroscopic studies on l-phenyl-3/7-naphtho[l,2-c]azepine and the isomeric l-phenyl-37/-naphtho[2,l-c]azepine indicate that in the [l,2-c]-isomer severe steric interactions between the phenyl group and the adjacent naphthalene ring prevent ring inversion at room temperature.39... 

In the UV spectral range complexation with 18-crown-6 causes a hypsochromic shift of the band with the longest wavelength in various solvents (Bartsch et al., 1976 Hashida and Matsui 1980). Gokel and Cram (1973) reported that complexation with binaphtho-20-crown-6 (11.2) produces a yellow to red color. This phenomenon is very likely to be due to a charge-transfer band between a naphthalene ring as donor (7i-base) and the arenediazonium ion as acceptor (7i-acid). 

The synthesis of the naphthalene rings found in the gilvocarcin group and in the rubromycin class of natural products via benzannulation was also reported. Both classes show promising antitumour activity [67,68]. 

A slightly related reaction involves the amino group of naphthylamines can be replaced by a hydroxyl group by treatment with aqueous bisulfite. The scope is greatly limited the amino group (which may be NH2 or NHR) must be on a naphthalene ring, with very few exceptions. The reaction is reversible (see 13-6), and both the forward and reverse reactions are called the Bucherer reaction. 

This concept was then extended to builder biaryl systems containing naphthalene rings.34,35 Biaryls 34-36 were all observed to undergo photochemically... 

Fluorescence. - A further report on the use of naphthalene phosphorus compounds for fluorescence derivatization concerns the dependence of fluorescence on the type and position of substituents on the naphthalene rings.141 It has been found that the... 

A number of products in which one of the naphthalene rings has been reduced have interesting pharmacological properties. Reaction of tetralone 30 with dimethylamine under TiCl catalysis produces the corresponding enamine (31). Reaction with formic acid at room temperature effects reduction of the... 

Typically in ring-opening reactions of aziridines, the amine functional group is retained in the product molecule. An example of such a reaction where the amine group has been lost has recently been reported <06TL977>. An intramolecular Friedel-Craft reaction of aziridine 91 leads to the expected product as an intermediate. Under the rather drastic reaction conditions, the sulfonamide is lost leading to formation of the naphthalene ring. 

All azo dyes contain one or more azo groups (-N=N-) as chromophore in the molecule on the basis of the number of azo groups in each molecule, they are named monoazo-, disazo-, trisazo-, etc. The azo groups are in general bound to a benzene or naphthalene ring, but they can also be attached to heterocyclic aromatic molecules or to enolizable aliphatic groups. On the basis of the characteristics of the processes in which they are applied, the molecule of the dye is modified to reach the best performances so they can be acid dyes, direct dyes, reactive dyes, disperse dyes, or others. 

The cycloadducts 25 and 26 have unique structures. Two isopropyl groups on the cyclotetrasilane ring are located over the benzene ring or the naphthalene ring. The short distances between the methine protons of the two isopropyl groups and the aromatic rings (25 2.81 and 2.86 A, 26 2.49 and 2.61 A) cause an upheld shift of the lH NMR signals of the methine protons (25 8 0.18 ppm, 26 8 —0.17 ppm) (Scheme 17). 

The most rapid reaction is N—N-dimerization (the rates of reactions A, B, C are related as 1 0.15 0.02 [94], Naphthylaminyl radicals recombine with the formation of N—C-dimers only [95], probably because voluminous naphthalene rings sterically hinder N—N-dimerization. A correlation between the rate constant of hyperfine splitting on the nitrogen atom of the aminyl radical and the rate constant of recombination of substituted ( (YC6H4)2N ) diphenyl-aminyl radicals was observed [95],... 

Although the observed products are consistent with initial formation of 4a, Untch proposed that they might arise via the intermediacy of cyclic allene 3a.23 Subsequent experiments by W.M. Jones and co-workers supported the initial formation of 3a in the dehydrohalogenation reactions, but left open the possibility of a rapid equilibrium between cycloheptatetraene (3a) and cycloheptatrienylidene (4a, Scheme 9).22,24 It was also found that fusion of benzene or naphthalene rings to different positions on the seven-membered ring strongly influenced whether a carbenic or allenic structure predominates.25... 

In 1,8-bis(dimethylamino)naphthalene steric and lone pair interactions are minimised in a structure (Einspahr et al., 1973) having the amino groups twisted and displaced above and below the plane of the naphthalene ring, as in [53] in which the almost planar naphthalene ring is shown as a dashed line. In l,8-bis(dimethylamino)-2,7-dimethoxynaphthalene, steric interactions involving the methoxy substituents bring about a further distortion as in [54] (Woolf, 1980). 

As an aside, it may be noted that the crystal structure of isoquinoline was reported recently (K. Hensen, R. Mayr-Stein, M. Bolte, Isoquinoline , Acta Crystallogr., Section C, 55,1565-1567). It is disordered and isostructural to naphthalene. Clearly, the introduction of a second heteroatom into the naphthalene ring brings with it interesting consequences. 

Here again the high reactivity is due to the gain of aromatic stabilization in the adduct. Polycyclic aromatics are moderately reactive as the diene component in Diels-Alder reactions. Anthracene forms adducts with a number of dienophiles. The addition occurs at the centre ring. The naphthalene ring system is much less reactive. 

In commercially important pigments, A typically stands for a benzene or a naphthalene ring, RD = Cl, CH3, C2H5, COOM, n = 0 through 2, and M is usually an alkaline earth metal, sometimes a manganese, aluminum, or sodium atom. 

Substitution reactions in the naphthalene ring take place, without exception, in the a-position, which is characterised by its high reactivity. 

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