Carbon catalyzed organic reactions: carbon promoted solvolysis of a phosphate ester derived from 1,1′-bi-2-naphthol

Abstract

Active carbons which catalyze the racemization of 1,1′-binaphthyl are not effective in racemizing the 2,2′-dihydroxyl and the 8,8′-dicarbomethoxyl derivatives of binaphthyl. The 2,2′-binaphthyl methyl phosphate ester derived from optically active 1,1′-bi-2-naphthol undergoes slow thermal racemization at 190 °C (t1/2 100 min, ▵H≠ 26.1 kcal/mol, ▵S≠ −21 cal/mol deg) in triglyme and this racemization rate is also unaffected by active carbon. However, in the hydroxylic solvent 2-(2-ethoxyethoxy)ethanol at 130 °C the rate of solvolysis of the phosphate ester is increased ca. tenfold by carbon blacks or decolorizing carbon at 1 mg/mL concentration. Control experiments show that the acceleration is not due to soluble impurities released by the carbons; heterogeneous catalysis, probably by acidic and/or nucleophilic functional groups on the carbon surfaces, is involved.