Electrophilic aromatic substitution naphthalenes

In addition to benzene and naphthalene derivatives, heteroaromatic compounds such as ferrocene[232, furan, thiophene, selenophene[233,234], and cyclobutadiene iron carbonyl complexpSS] react with alkenes to give vinyl heterocydes. The ease of the reaction of styrene with sub.stituted benzenes to give stilbene derivatives 260 increases in the order benzene < naphthalene < ferrocene < furan. The effect of substituents in this reaction is similar to that in the electrophilic aromatic substitution reactions[236]. 

Polycyclic aromatic hydrocarbons undergo electrophilic aromatic substitution when treated with the same reagents that react with benzene In general polycyclic aromatic hydrocarbons are more reactive than benzene Most lack the symmetry of benzene how ever and mixtures of products may be formed even on monosubstitution Among poly cyclic aromatic hydrocarbons we will discuss only naphthalene and that only briefly Two sites are available for substitution m naphthalene C 1 and C 2 C 1 being normally the preferred site of electrophilic attack... 

The polycyclic aromatic hydrocarbons such as naphthalene, anthracene, and phenan-threne undergo electrophilic aromatic substitution and are generally more reactive than benzene. One reason is that the activation energy for formation of the c-complex is lower than for benzene because more of the initial resonance stabilization is retained in intermediates that have a fused benzene ring. 

The y-nitrogen atom of a sulfonic acid azide is electrophilic and reacts in an electrophilic aromatic substitution with an activated benzene or naphthalene derivative, e.g., a phenoxide ion, forming a l-tosyl-3-aryltriazene (2.47). The 1,4-quinone diazide is obtained by hydrolysis (Scheme 2-30, Tedder and Webster, 1960). The general applicability of this reaction seems to be doubtful. With 1-naphthol the 1,2-naphthoquinone diazide was obtained, not the 1,4-isomer. 

How many different compounds can be produced when naphthalene, C 0Hjj (30), undergoes electrophilic aromatic substitution by a single electrophile (denoted E) Draw stick figures to represent them. 

The quantum-chemical calculation of charge-transfer states as possible intermediates in electrophilic aromatic substitution reactions, making allowance for solvation effects, has been reviewed.6 It has been shown that a simple scaled Hartree-Fock ab initio model describes the ring proton affinity of some polysubstituted benzenes, naphthalenes, biphenylenes, and large alternant aromatics, in agreement with experimental values. The simple additivity rule observed previously in smaller... 

The text points out that C-l of naphthalene is more reactive than C-2 toward electrophilic aromatic substitution. Thus, of the two possible products of sulfonation, naphthalene-1-sulfonic acid should be formed faster and should be the major product under conditions of kinetic control. Since the problem states that the product under conditions of thermodynamic control is the other isomer, naphthalene-2-sulfonic acid is the major product at elevated temperature. 

A review of solvent properties of, and organic reactivity in, ionic liquids demonstrates the relatively small number of quantitative studies of electrophilic aromatic substitution in these media.3 Studies mentioned in the review indicate conventional polar mechanisms. 1-Methylpyrrole reacts with acyl chlorides in the ionic liquid 1-butylpyridinium tetrafluoroborate to form the corresponding 2-acylpyrrole in the presence of a catalytic amount of ytterbium(III) trifluoromethanesulfonate.4 The ionic liquid-catalyst system is recyclable. Chloroindate(III) ionic liquids5 are catalytic media for the acylation, using acid chlorides and anhydrides, of naphthalene, benzene, and various substituted benzenes at 80-120 °C. Again the ionic liquid is recyclable. 

Polycyclic aromatic compounds also undergo electrophilic aromatic substitution reactions. Because the aromatic resonance energy that is lost in forming the arenium ion is lower, these compounds tend to be more reactive than benzene. For example, the brotni-nation of naphthalene, like that of other reactive aromatic compounds, does not require a Lewis acid catalyst ... 

Electrophilic aromatic substitution usually occurs at the 1-position of naphthalene, also called the a position. Predict the major products of the reactions of naphthalene with the following reagents. 

Naphthalene undergoes electrophilic aromatic substitution at C-1 more easily than at C-2. There is a smaller loss of resonance energy in forming the intermediate for reaction at C-1 and reaction takes place more rapidly at this centre. However, the products of aromatic substitution at C-1 suffer interactions with C-8 (peri interactions) and are less stable than the corresponding products of substitution at C-2. Hence those aromatic substitution reactions that are carried out under conditions that allow equilibration between isomers (thermodynamic control) lead to substitution ai C-2, but reactions that are carried out under conditions... 

Although two products (A and B) are possible when naphthalene undergoes electrophilic aromatic substitution, only A is formed. Draw resonance structures for the intermediate carbocation to explain why this is observed. 

The major products of further substitution in a monosubstituted naphthalene can usually be predicted by the following rules. As we shall see, these rules are reasonable ones in light of structural theory and our understanding of electrophilic aromatic substitution. 

Naphthalene undergoes electrophilic aromatic substitution at the position next to the second ring. The sigma complex leading to the obtained product has more resonance structures, indicating a more delocalized charge than that of the alternative. 

This reaction was introduced in Section 4.6, Electrophilic Substitution at a Trigonal Planar Center. The electrophile adds to the pi bond of the aromatic ring, path Ag, followed by deprotonation of the cation formed, path Dg, restoring aromatic stabilization. See Section 5.6 Aromatic Rings, for a discussion of electrophilic aromatic substitution on heteroaromatics like pyridine and on condensed aromatics like naphthalene. 

Also like benzene, naphthalene undergoes electrophilic aromatic substitution reactions. Substitution occurs preferentially at the 1-position. In common nomenclature, the 1-position is called the a-position and the 2-position is called the j8-position. 

Draw the resonance contributors for the carbocation intermediates obtained from electrophilic aromatic substitution at the 1-position and the 2-position of naphthalene. Use the resonance contributors to explain why substitution at the 1-position is preferred. 

Polycyclic benzenoid hydrocarbons contain two or more fused benzene rings fused rings share two adjacent carbons. Polycychc benzenoid hydrocarbons undergo electrophilic aromatic substitution reactions. Naphthalene undergoes irreversible substitution predominantly at the 1-position and reversible substitution predominantly at the 2-position. The nature of the substituent determines which ring of a substi-tuted-naphthalene undergoes electrophilic substitution. 

Electrophilic aromatic substitution reactions of naphthalene (Section 16.16)... 

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