Isomerization, Disproportionation, and Polycondensation of Methylnaphthalenes in a Melt Containing Aluminium Chloride as the Main Constituent

Abstract

Methylnaphthalenes(0.01 mol) as simplified models of the constituents of tar were heated at 100° C for 2-30 min in a melt consisting of A1Cl3, NaCl, and KCl(0.60, 0.26, and 0.14 mol, respectively; a standard melt, mp 95° C). Monomethylnaphthalenes (MMN) isomerized rapidly giving an equilibrium mixture (2-/1-MMN=4.4), and at the same time they formed small amounts of naphthalene, dimethylnaphthalenes (DMN), and tetralin. In the reaction of DMN, as shown in Table 2, generally 1, 3-DMN was the main product, being accompanied with isomeric DMNs, MMNs, trimethylnaphthalenes (TMN), a dihydro-DMN, and tarry condensation products. The reactivity of DMNs was as follows: 1, 8--, ---1, 4->2, 3->2, 6->1, 3- > 1, 2-DMN.
The isomerization as well as other reactions was accelerated by the addition of CF, SO, H. The use of ZnCl2 instead of A1Cl3 resulted in no reaction.
When heated at 120° C for 2 hr in the standard melt, 2, 3-DMN and 2, 6-DMN gave the respective tars, the NMR spectra of which were almost coincident each other, and by the same way an equimolar mixture of 2-MMN and 2, 3, 6-TMN gave a tar, the NMR spectrum of which was closely similar to the above ones.