Browsing by Author "Mobili, P."
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- Thermally induced sigmatropic isomerization of pseudosaccharyl allylic etherPublication . Gómez-Zavaglia, A.; Kaczor, A.; Almeida, R.; Cristiano, Maria Lurdes Santos; Eusébio, M. E. S.; Maria, T. M. R.; Mobili, P.; Fausto, R.The thermally induced sigmatropic isomerization of the pseudosaccharyl allylic ether [3-(allyloxy)-1,2-benzisothiazole 1,1-dioxide; ABID] has been investigated by a multidisciplinary approach using temperature dependent infrared spectroscopy, differential scanning calorimetry, and polarized light thermomicroscopy, complemented by theoretical methods. Migration of the allylic system from O to N occurs in the melted ABID, and the thermally obtained 2-allyl-1,2-benzisothiazol-3(2H)-one 1,1-dioxide (ABIOD) starts to be produced at ca. 150 °C, in a process with an activation energy of ∼92 kJ mol-1. From kinetic data, a concerted [3,3′] sigmatropic mechanism is proposed. In the temperature range investigated, ABIOD was found to exhibit polymorphism. Cooling of the molten compound leads to the production of a metastable crystalline form, which upon annealing at room temperature might be transformed to the stable crystalline phase. ABID shows a single crystalline variety. Assignments were proposed for the infrared spectra of the observed neat condensed phases of the two compounds.