Naphthalene molecular structure

Figure 14-20. Molecular structure of naphthalene tctracarboxylic dianliydridc (NTCDA) and perylene letracarboxylic dianhydridc (PTCDA).

Molecular solids are aggregates of molecules bound together by intermolecular forces. Substances that are gases under normal conditions form molecular solids when they condense at low temperature. Many larger molecules have sufficient dispersion forces to exist as solids at room temperature. One example is naphthalene (Cio Hg), a white solid that melts at 80 °C. Naphthalene has a planar structure like that of benzene (see Section 10-), with a cloud of ten delocalized n electrons that lie above and below the molecular plane. Naphthalene molecules are held in the solid state by strong dispersion forces among these highly polarizable n electrons. The molecules in... 

Molecular structure can have a profound effect on the position in the spectrum where fluorescence occurs, as well as on its intensity. It can be shown by quantum mechanics that the more extended a conjugated system is, the smaller will be the separation in energy between the ground state and the lowest excited singlet state. This is evident in the fact that benzene, naphthalene, and anthracene, having one, two, and three rings, fluoresce maximally at 262 nm, 320 nm, and 379 nm, respectively. 

Even simple dienes and polyenes are difficult to classify in comparison with alkenes. Whereas bromination, oxidation and reaction with tetranitromethane (TNM) can identify the number of double bonds and their location in the molecular structure, conjugated double bonds produce very complex mixtures. Furthermore, many of the tests based on 7r-complexation can also apply for aromatic moieties. An example is the TNM 7r-complex which is yellow with benzene and orange with naphthalene and the tests are therefore non-specific. 

In addition to CN and ON, the smoke point (SP), which is the maximum smoke-free laminar diffusion flame height, has been employed widely to evaluate the tendency of different fuels to form soot. This tool was first applied to kerosenes, later diesel, and then jet engine fuels.19,20 Researchers have tried to relate smoke points of pure compounds to their molecular structure. It was found that the inverse of smoke point, which measures the potential of a fuel to form soot, increases from n-paraffins to iso-paraffins to alkylbenzenes to naphthalenes.21,22 Since smoke points vary with experimental conditions, the concept of a threshold soot index (TSI), which is calculated from the smoke point, molecular weight, and experimental constants, has been used to compare the soot-formation tendencies of different fuel molecules.23... 

The knowledge and good control of new dianionic species like 8 substituted naphthalene dianions is a very attractive tool to tailor block copolymers with the new molecular structure. This approach can be applied to develop new materials enjoying original and useful sets of properties. 

Dyes, Dye Intermediates, and Naphthalene. Several thousand different synthetic dyes are known, having a total worldwide consumption of 298 million kg/yr (see Dyes and dye intermediates). Many dyes contain some form of sulfonate as —S03H, —S03Na, or — SC NH. Acid dyes, solvent dyes, basic dyes, disperse dyes, fiber-reactive dyes, and vat dyes can have one or more sulfonic acid groups incorporated into their molecular structure. The raw materials used for the manufacture of dyes are mainly aromatic hydrocarbons (67—74) and include benzene, toluene, naphthalene, anthracene, pyrene, phenol (qv), pyridine, and carbazole. Anthraquinone sulfonic acid is an important dye intermediate and is prepared by sulfonation of anthraquinone using sulfur trioxide and sulfuric acid. 

The molecular structure of (64) may be considered as a pentagonal bipyramid with the naphthalene, the chlorine and two phosphorus atoms in the pentagonal plane. It is structurally related to (53) by a 45° rotation of the naphthalene unit about the Ta—Cl vector. The temperature dependent 1H and 31PNMR spectra indicate that such a process is operative in solution. The structural parameters suggest that the jr-accepting interaction is substantial this is consistent with the inertness of the Ta-naphthalene unit toward substitution. 

At pressures of 13 GPa many carbonaceous materials decompose when heated and the carbon eventually turns into diamond. The molecular structure of the starting material strongly affects this process. Thus condensed aromatic molecules, such as naphthalene or anthracene, first form graphite even though diamond is the stable form. On the other hand, aliphatic substances such as camphor, paraffin wax, or polyethylene lose hydrogen and condense to diamond via soft, white, solid intermediates with a rudimentary diamond structure (29). 

Interestingly, the molecular structure of the 2,7-naphthyl catalysts 39 and 40 markedly resembles that of the 1,3-phenyl catalysts 37 and 38, respectively the only difference is the distance between the two cinchona alkaloid units. The naphthalene linker is about 2.4 A longer than the benzene linker. The Park-Jew group proposed that the reason for the higher enantioselectivity of the 2,7-naphthyl catalyst was that the 2,7-naphthalene linker might confer a spatial benefit to form a more favorable conformation by decreasing the steric hindrance between the two cinchona units compared to that in the 1,3-benzene linker. 

It has been known for many years that molecular structure of a fuel has a direct bearing on the tendency of that fuel to smoke, i.e., to form carbon or soot in a flame. For example, in 1954 Schalla (41), reporting on a study of diffusion flames, indicated that the rate at which hydrocarbons could be burned smoke free varied in the order n-paraffins — mono-olefins — alkynes — aromatics. This same phenomena has been reconfirmed by many authors in a variety of systems and always in the same general order (j6, J3, J 5, 1 7, J 9, 26, 43, 45). Paraffins have the least tendency to smoke, whereas the naphthalene series have the greatest tendency to smoke. 

D. W. J. Cruickshank, A detailed refinement of the crystal and molecular structure of Naphthalene, Acta Cryst. 10 504—508 (1957). 

Tetrathieno[2,3- 3, 2 - 2",3"-/3", 2" - ]naphthalene 42 forms a 1 1 complex with tetracyano- -quinodimethane (TCNQ). X-Ray crystal structure determination of the complex confirms the molecular structure and reveals a onedimensional (1-D) structure with columns of alternating donor (D) and acceptor (A) moieties. The flat molecules stack on top of each other with a plane-to-plane D-A distance of 3.32(2) A. As a consequence of this structure, the material is fully insulating as confirmed by a compressed pellet conductivity measurement. 

The molecular structures and electron distributions of the 1,8-bis-(dimethylamino)-naphthalenes, studied by density functional and ab initio MP2 calculations ... 

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