874-35-1

Pyrolysis of 2,6-tetramethylene Dewar benzene (2a) under flash vacuum thermolysis (FVT) conditions at 400 deg C gave 6- and 5-methylindan (8a (2.5percent) and 10a (2.5percent), respectively) as well tetralin (5a) (45percent).These products indicate that metacyclophane (1a) was formed in the gas phase, but it decomposed under the reaction conditions either via homolytic cleavage of one of the benzylic bonds to yield a diradical (6a) leading to 8a and 10a or it gave 5a via benzvalene intermediate (4a).Deuterium labeling supports the proposed mechanism.A very similar course of events was observed on FVT of metacyclophane at 600 deg C; it yielded methyl-substituted tetralins (8c, 10c) as the sole products.The analogies and differences in the behavior of the two metacyclophanes are discussed.

Composition of the low-boiling fraction of the pyrolysis oil obtained from continuous rectification has been determined by combination of capillary gas-liquid chromatography with other identification methods (catalytic hydrogenation, polymerization).In this way components have been identified which form overall 86.0 per cent (m/m) of the low-boiling fraction.The said pyrolysis oil fraction has been found to contain almost 50 per cent (m/m) of unsaturated components able of polymerization, especially methylindenes, methyl-, ethyl- and dimethylvinylbenzenes, divinylbenzenes and 1,2-dihydronaphthalene.Elution behaviour of all the identified isomeric methylindenes, divinylbenzenes and 1,2-dihydronaphthalene has been evaluated by determination of parameters of the equation Ist.phase(2) = k.Ist.phase(1) + q. The Kovats elution indices of all the identified aromatic hydrocarbons have been determined with the use of a glass capilary column wetted with Carbowax 20M at 80o C.