Cas-Liquid-phase Reactions Substitution

Synthetic phenol capacity in the United States was reported to be ca 1.6 x 10 t/yr in 1989 (206), almost completely based on the cumene process (see Cumene Phenol). Some synthetic phenol [108-95-2] is made from toluene by a process developed by The Dow Chemical Company (2,299—301). Toluene [108-88-3] is oxidized to benzoic acid in a conventional LPO process. Liquid-phase oxidative decarboxylation with a copper-containing catalyst gives phenol in high yield (2,299—304). The phenoHc hydroxyl group is located ortho to the position previously occupied by the carboxyl group of benzoic acid (2,299,301,305). This provides a means to produce meta-substituted phenols otherwise difficult to make (2,306). VPOs for the oxidative decarboxylation of benzoic acid have also been reported (2,307—309). Although the mechanism appears to be similar to the LPO scheme (309), the VPO reaction is reported not to work for toluic acids (310). 

The difference between the enthalpies of formation of gas-phase 1- and 2-naphthylamine of some 22 kJmol-1 is troubling. It is quite inexplicable when the likewise related differences between 1- and 2-methylnaphthalene, and of 1- and 2-naphthol, all but vanish50. The accuracy of the enthalpy of formation values can be assessed with equation 10, which is related to equation 2, and is expected to be thermoneutral when all substances are in the same phase. For the solid or liquid phase and for 1-naphthylamine, and for the solid-phase 2-naphthylamine, the enthalpy of reaction is in the range of — 1.1 to 5.4 kJ mol-1. For gas-phase 2-naphthylamine, the enthalpy of reaction is the discrepant —21 kJmol-1. There being no apparent reason why this reaction should not be approximately thermoneutral also, a calculated enthalpy of formation of gaseous 2-naphthylamine is ca 155 kJ mol-151. However, in clear conscience we cannot recommend remeasurement of either (or even better, both) naphthylamines because the 2-isomer is such a powerful carcinogen. Perhaps with appropriate substitution that is simultaneously sterically and electronically innocuous and that also renders the amine toxicologically innocuous, relevant measurements can (and thus should) be made. 

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