Resonance structures naphthalene

In general the most stable resonance structure for a polycyclic aromatic hydro carbon is the one with the greatest number of rings that correspond to Kekule formula tions of benzene Naphthalene provides a fairly typical example... 

Fill in the multiple bonds in the following model of naphthalene, c,0h8 (gray - C, ivory = FI). How many resonance structures does naphthalene have ... 

Azulene, an isomer of naphthalene, lias a remarkably large dipole moment for a hydrocarbon (/i = 1.0 D). Explain, using resonance structures. 

Look at the three resonance structures of naphthalene shown in Section 15.7, and account for the fact that not all carbon-carbon bonds have the same length. The C1-C2 bond is 136 pm long, whereas the C2-C3 bond is 139 pm long. 

Draw resonance structures of the intermediate carbocations in the bromillation of naphthalene, and account for the fact that naphthalene undergoes electrophilic substitution at Cl rather than C2. 

Problem 10.14 (a) Draw three resonance structures for naphthalene, (b) Which structure makes the major contribution to the structure of the hybrid in that it has the smallest energy (c) There are four kinds of C-to-C bonds in naphthalene C -C , C -C , C -C , and C -C ". Select the shortest bond and account for your choice. 

The configurations of the molecules are those expected for the resonating structures. Through resonance each bond acquires some doublebond character, which causes the adjacent bonds to strive to be co-planar. The molecules are thus brought into completely planar configurations, with 120° bond angles. This has been verified for naphthalene and anthracene and many larger aromatic hydrocarbons by careful x-ray studies. 

Draw all the octet resonance structures of (a) benzene, C6H6, and (b) naphthalene, CioHs. Benzene is known to have a hexagonal symmetry, and the carbon framework of naphthalene consists of two fused hexagons in the same plane. 

If we now consider the a and it bondings, formula 82 for both resonance structures has twelve or ten it electrons according to whether or not we admit that every sulfur atom retains only two unshared electrons on the M level. So the no bond resonance does not show the existence of a naphthalene-like 107r-eleetron system. If dotted lines are used to represent half bonds, the system con-... 

Naphthalene, which has two benzene-type rings fused together, provides a more interesting test for the predictive powers of resonance theory. There are three resonance structures for naphthalene, each with alternating single and double bonds around the rings ... 

Three resonance structures can be written for naphthalene. Note that the C-l —C-2 bond is a double bond in two of these structures and a single bond in one, while the C-2—C-3 bond is a single bond in two structures and a double bond in one. This explains why the C-l —C-2 bond is shorter than the C-2—C-3 bond. 

Huckel s rule applies only to compounds with a single ring, such as benzene and cyclobutadiene. However, it can be used with multiple-ring compounds if the resonance structure with all of the double bonds on the periphery of the ring is considered. For example, using such a structure for naphthalene shows 10 electrons in the cycle, so it is predicted to be aromatic. 

Note that both the bromination and the acylation of naphthalene result in the substitution of the electrophile at the 1 position. None of the isomeric product with the electrophile bonded to the 2 position is isolated in either case. The higher reactivity of the 1 position can be understood by examination of the resonance structures for the arenium ion. When the electrophile adds to the 1 position, the arenium ion has a total of seven resonance structures, whereas only six exist for the arenium ion resulting from addition of the electrophile to the 2 position. 

Draw the seven resonance structures for the arenium ion formed in the bromination of naphthalene at the 1 position and the six resonance structures formed in bromination at the 2 position. 

Naphthalene Naphthalene (C10H8) is the simplest fused aromatic compound, con- Hydrocarbons sisting of two fused benzene rings. We represent naphthalene by using one of the three Kekule resonance structures or using the circle notation for the aromatic rings. 

Figure 10. Schematic illustration of a tendency of each benzene fragment in naphthalene to retain its aromaticity by producing cis 1,3-butadiene partial localization in its twin-ring as described by the resonance structures (7a) and (7b) yielding the resulting predominant canonical structure (7c). This intuitive argument is supported by the (HF/6-31G ) bond distances and the corresponding 7r-bond orders given within parentheses.

As the number of fused benzene rings increases, the number of resonance structures increases as well. Although two resonance stmctures can be drawn for benzene, naphthalene is a hybrid of three resonance structures. 

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. 

First, draw a structure, 1-16, for naphthalene that shows alternating single and double bonds around the periphery. This is one of the resonance structures that contributes to the character of delocalized naphthalene, a resonance hybrid. 

Figure K-1. The three Kekul6 resonance structures of naphthalene.

Fill if- the wiiltiple bonds in the foUcrwing model of naphthalene, C oHh (gray >= C. ivory = ffi. How many resonance structures [Pg.88]

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