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The objective of this investigation was to demonstrate hindered rotation about single bonds in certain simple paracyolophanes. This purpose was achieved by the resolution of a suitable o-substituted paracyclophane which had ten carbon atoms in its para-bridge, as exemplified by the compound [10] paracyclophane-12-carboxylie acid. This acid was synthesized in three steps from [10]paracyclophane: [10]paracyclophane -* 12-chloromethy 1 [10]paracyclophane (73%) -[10]paracyclophane-12-carboxaldehyde (84%) -» [10]paracyclophane-12-carboxylic acid (45%). Resolution of the racemic acid, m.p. 192-193°, into its pure optical antipodes was accomplished by separation of its cinchonidine salts. The active forms of the acid, m.p.'s ca. 160°and « ± 80°, racemized slowly at room temperature in the solid, crystalline state. Illustrative of some of the difficulties encountered early in this study was the observation that succinoylation of [10] paracyclophane gave only the rearranged product 12-( -carboxypropionyl) [10-m] cyclophane, a compound unsuitable for the purpose of this study.

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