The thermal racemization of polycrystalline samples of neat (+)-bicyclo[2.2.1]hept-5-ene-íran¿-2,3dicarboxylic acid (mp 176°) has been studied from 130 to 194°. Up to 165°the reaction occurs in the solid state (AH* = 40.0 kcal/mol, AS -= 14 eu) at a rate only ca. one-tenth of the melt rate extrapolated to these temperatures (for the melt at 176-194°, AH* = 29.7 kcal/mol, 5* = -6.9 eu). The strictly first-order solid-state reaction has no inhibition period and is unaffected by crystal size or optical purity of samples. This reverse Diels-Alder reaction and recombination occur throughout the bulk of polycrystalline sample rather than at crystal defects or impurity sites. X-Ray diffraction patterns of partially racemized samples taken from runs below the eutectic temperature of 165°show growth of (±)-racemic compound (mp 186°).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.