1.2- Dimethylenecyclohexane

From enthalpy of formation data of 63 from Roth, and for the other species from Pedley, we find reaction 30 is exothermic by 6 kJ mol 1. Consider now the isomeric 1,3-and 1,4-dimethylenecyclohexane, 65 and 66 no thermochemical data for its 1,2-isomer are seemingly available. We can write the related formal reactions 31a and 31b. 

It is preferable to prepare and use various diisocyanide ligands (trimethylene to octamethylenene diisocyanides, 1,4-dimethylenecyclohexane and 1,3-xylylidene diisocyanides) as solvent solutions rather than as isolated materials, because violent explosions have been observed dining vacuum distillation of these ligands [1]. Four such ligands were, however, distilled uneventfully [2]. Individually indexed compounds are ... 

The franx-dioxirane 15 is formed in good yield from 1,4-dimethylenecyclohexane by peracid attack from the axial side. ... 

The synthesis and polymerization characteristics of 1,4-dimethylenecyclohexane are described. Cationic polymerization of this monomer yields relatively low molecular weight polymers containing appreciable amounts of endocyclic double bonds. In contrast to our earlier claim, 1,4-dimethylenecyclohexane does not seem to cyclopolymerize to a significant extent. 

This paper concerns the polymerization behavior of 1,4-dimethylenecyclohexane, I, a monomer that was claimed in an earlier report (9) to polymerize cationically to afford a soluble, essentially saturated polymer that was presumed to have the bicyclic repeating structure II. 

Dimethylenecyclohexane was synthesized in 54 percent yield by the following reaction. The material was shown by gas-liquid chromatography to be better than 99 percent pure. 

In Figure 1. It is seen that the yield increases with monomer concentration up to about 2 M. It then falls at higher concentrations, presumably because of the influence of monomer on the dielectric constant of the reaction mixture. Table I summarizes the results obtained in studies on the cationic polymerization of 1,4-dimethylenecyclohexane. 

Figure 1. Effect of 1,4-dimethylenecyclohexane concentration on polymer yield for polymerizations conducted at —78°C using CHtCl as solvent and BFS as...

Figure 3. 300 MHz 1H-NMR spectrum of poly( 1,4-dimethylenecyclohexane), Sample 22, in CClA solution.

The above reactions can explain the incorporation of units with endocyclic unsaturation into the polymers. The highly hindered endocyclic double bonds present in such structures probably have low polymerization ceiling temperatures and would resist polymerization. They could be difficult to brominate or hydrogenate. It is our failure to appreciate the limited reactivity of endocyclic double bonds in structures such as IV, IX and X that caused us to overlook them in our original investigation (9). This limited reactivity also explains why soluble polymers can be formed in 1,4-dimethylenecyclohexane polymerizations even when cyclopolymerization does not seem to occur. 

It thus appears that the principal structural features found In poly(1,4-dimethylenecyclohexane) can be explained by conventional carbonium ion chemistry. There is no indication that cyclopolymerization occurs in these polymerizations and there is much evidence to indicate that the double bonds present in this diene react independently. Some of them are involved in polymerization reactions, but a large proportion isomerize to relatively stable endocyclic double bonds. Under polymerization conditions where isomerization is favorable, soluble, unsaturated polymers having complex structures are obtained. When isomerization reactions are not favorable (low temperatures, use of Ziegler-Natta catalysts), the double bonds polymerize independently and crosslinked products are obtained. 

Polymerization of 1,4-Dimethylenecyclohexane with BF3 - A 100 ml two-neck flask was rinsed with dilute NH3 solution and dried in air at 150°C. While still hot, the flask was flushed with nitrogen and one of the necks was equipped with a rubber gum... 

Aue found that [3.2.1]propellane opened to 1,3-dimethylenecyclohexane at 318°C (Scheme 9.100)/ The temperature necessary to affect this retro 2 + 2 cycloaddition is much higher than that for the retro 2 + 2 cycloaddition of [2.2.2]propellane to 1,4-dimethylenecyclohexane studied by Eaton which occurs at only 25°C/ ... 

Nucleophilic substitution with sodium sulphide has been used to prepare thiapropellanes (Scheme 27), The sulphone of (129) was very unstable thermally and readily gave 1,4-dimethylenecyclohexane (see further Hoffman and Stohrer, /. Amer. Chem. Soc., 1972, 94, 779). Further salts of (130) and (131) are described. 

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