By empioying deuterium substitution and metastable ion defocusing methods, it has been determined that l-acetoxytetral¡n undergoes a híghiy regiospecific ( > 98% ) 1,4-el¡mination of acetic acid. The mechmbm closely parallels that for loss of water from 1-tetralol in terms of specificity. However, unlike the water loss, which shows a significant irbetic isotope effect (k,/kD=2.0) and a large release of translationai energy (270 meV), the expuision of acetic acid occurs without an isotope effect and with release of oniy 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-acetoxytetraiin exhibits the more traditional l,Z-elimination of acetic acid which contrasts with a 1,3-el¡mination of water for the corresponding alcohol.