78299-02-2Relevant academic research and scientific papers
Acid-catalysed aromatization of anthranyl derivatives. A kinetic and thermodynamic study
Pirinccioglu,Jia,Thibblin
, p. 2271 - 2275 (2001)
The acid-catalysed solvolysis reaction of 9-methoxy-9-methyl-9,10-dihydroanthracene (2-OMe) in 50 vol percent acetonitrile in water at 25°C provides the substitution product 9-hydroxy-9-methyl-9,10-dihydroanthracene (2-OH) and the elimination product 9-methylanthracene (3). The rate-ratio of substitution-to-elimination was measured as kS/kE = 0.93. The alcohol also undergoes acid-catalysed aromatization to give the thermodynamically favoured product 3. The reaction enthalpy of this dehydration reaction was measured as ΔH = -10.2 ± 1.0 kcal mol-1. The corresponding reaction of the secondary alcohol 9-hydroxy-9,10-dihydroanthracene (1-OH) has a reaction enthalpy of ΔH = -12.3 ± 0.8 kcal mol-1. Addition of azide ion (0.25 M) gives rise to a large fraction of azide adduct 2-N3, which rapidly undergoes solvolysis. The "azide-clock" method yields rate constants for reaction of the carbocation to give alcohol and elimination product ofkw = 2.2 × 108 s-1 and ke = 2.4 x 108 s-1, respectively. The thermodynamic stability of the carbocation was estimated as pKR = -9.1. The alkene 9-methylene-9,10-dihydroanthracene (4) undergoes a slow acid-catalysed aromatization to give 3; no competing formation of 2-OH was observed.
