Naphthalenes and Tetralins

There are many examples in the literature of the exchange of aromatic hydrogens in benzene, naphthalene and tetralin derivatives which employ... 

Table CIIL Dipole Moments of ot and fi Monosubstituted Derivatives of Naphthalene and Tetralin ...

Representative yields of trans-decalin as a function of conversion are shown in Figs. 4 and 5. These experiments included two different feeds (naphthalene and tetralin), two different catalyst supports (alumina and charcoal), and a range of temperatures. Figure 4 shows that ruthenium is highly selective for the formation of ci -deoalin. In the... 

The mechanism of formation of volatiles has been clearly demonstrated. Jellinek and Spencer [60] have proved the radical nature of the production of volatiles by studying the degradation of polystyrene in naphthalene and tetralin solutions. The formation of volatiles is, in fact, completely inhibited in the last solvent which contains a-methylenic hydrogen atoms which are able to deactivate free radicals. The rate of volatilization has also been shown to be proportional to the number of chain ends [61(a)], a result confirmed by Cameron [61(b)]. The... 

Degradation in the presence of solvents has also been applied to the conversion of other styrenic polymers, such as poly(p-methylstyrene) and poly(styrene-allyl alcohol).64,65 Figure 4.11 shows the temperature dependence of the conversion of poly(p-methylstyrene) when using phenol, 1-methyl-naphthalene and tetralin as solvents. In this case, tetralin leads to the greatest degradation below 370 °C, whereas the order is reversed above that temperature. These results indicate that the effect of the solvent in the degradation of styrenic polymers is strongly influenced by the temperature. 

Thermodynamic reaction equilibrium for the naphthalene and tetralin hydrogenation to decalins was calculated according to Gibb s free energy change by the FLOWBAT program [12]. The results predict full conversion of both n hthalene and tetralin to decalins under the conditions studied. Moreover, thermodynamics favours the formation of trans-decalin, 93.5-96.6% in the temperature range 85-160°C [12]. The thermodynamic equilibrium of and A -octalin was not calculated since the required thermodynamic properties were not available. Weitkamp [7] has reported that the equilibrium ratio of the octalins varies from 15 to 3.5 at 0-200 C (5.9 and 3.6 at 100 and 177°C, respectively), with A -octalin the major component. 

Overall reaction rates for the naphthalene and tetralin were based on generalised Langmuir-Hinshelwood kinetics [14] according to equations 7 and 8. Temperature dependency of rate constants ko, k and kr was described by Arrhenius law and adsorption equilibrium constants by the van t Hoff equation. 

The adsorption entropy and enthalpy of naphthalene (80 J/molK and 13 kJ/mol, respectively) were higher than the entropy and enthalpy of tetralin (60 J/molK and 5 kJ/mol) or hydrogen (64 J/molK and 5 kJ/mol). The higher enthalpy of naphthalene is indicative of the stronger adsorption of naphthalene, which was also qualitatively observed (see 3.3 Naphthalene and Tetralin Conversion). However, these adsorption parameters indicate that the adsorbed compounds, which are active for the hydrogenation, are fairly mobile on the surface and their adsorption is energetically weak. 

Methylation of naphthalene and tetralin therefore can be accomplished only in very poor yields. Similarly such reactive heterocyclic aromatic substances as furan and thiophene, have not been alkylated successfully by the Friedel-Crafts method. Deactivation of the furan nucleus by the carboxyl group of furoic acid, however, makes alkylation by the Friedel-Crafts procedure feasible and useful (see Table XV, p. 76). 

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