Saturated para-Hydrogen

Saturated Liquid Densities of Oxygen, Nitrogen, Argon and Para-Hydrogen (National Bureau of Standards Technical Note 361), National Institute of Standards and Technology, Gaithersburg, MD 20899. 

Synthesis of Camphor.— The relationship of camphor to pinene, the terpene present in turpentine, is of especial interest and importance in connection with its synthesis. Pinene is the unsaturated di-cyclic terpene related to the saturated di-cyclic terpene pinane (p. 823). In both of these terpenes the di-cyclic arrangement is different from that in camphane and Bornylene in that the isopropyl group in forming the secondary cycle joins the meta carbons instead of the para. Now pinene, by addition of hydrogen chloride, forms a hydrochloride which has been referred to as artificial camphor. This hydrochloride is identical with the hydrochloric acid ester of Bomeol and may be converted into Bomeol by hydrolysis. Now as Bomeol can be oxidized to camphor we may thus obtain true synthetic camphor from pinene. The reactions, involving an intermediate product and then rearrangement of the secondary cycle in pinene, are as follows ... 

Partial hydrogenation of either the ortho or meta terphenyl (33) over platinum or copper chromite results in the saturation of the internal ring (Eqn. 17.29) but hydrogenation of para terphenyl (34) takes place primarily on a terminal ring (Eqn. 17.30). ... 

The composition of the mixtures obtained from the xylenes resembles the pattern for the isomeric olefins, the j>er cent of the ds isomer decreasing in the series ortho > meta > para. The same order was noted in the hydrogenation of the isomeric phthalic acids over PtOj in acetic acid (4). The trans isomer is not formed by isomerization of the saturated ds form because more trans-1,3-dimethylcyclohexane is produced from m-xylene than is contained in the equilibrium mixture of the 1,3-isomers. 

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