The mechanism for elimination of acetic acid from 1‐acetoxy‐ and 2‐acetoxytetralin

By employing deuterium substitution and metastable ion defocusing methods, it has been determined that 1‐acetoxytetralin undergoes a highly regiospecific (>98%) 1,4‐elimenation of acetic acid. The mechanism closely parallels that for loss of water from 1‐tetralol in terms of specificity. However, unlike the water loss, which shows a significant kinetic isotope effect (K_H/K_D = 2.0) and a large release of translational energy (270 meV), the expulsion of acetic acid occurs without an isotope effect and with release of only 10 meV of kinetic energy. Competitive with acetic acid loss is the elimination of ketene which has been shown to occur by a 4‐centered transition state. The 2‐acetoxytetralin exhibits the more traditional 1,2‐elimination of acetic acid which contrasts with a 1,3‐elemination of water for the corresponding alcohol.