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Free keywords:
Epoxidation;
Terpenes;
DFT calculation;
Alumina;
Hydrogen peroxide
Abstract:
The selectivity of the alumina catalyzed epoxidation of (S)-limonene, citronelal, citral, citronelol and (1S)-(α)-pinene with aqueous 70 wt% and anhydrous 24 wt% hydrogen peroxide is described. DFT molecular orbital calculations were used aiming at a better understanding of the reactivity of these terpenes. The more nucleophilic carbon–carbon double bond, which has a higher molecular orbital energy, is preferentially epoxidized (site-selectivity). Furthermore, a preference for epoxidation in competition with other possible reactions is observed for citronelal, citral, citronelol and (1S)-(α)-pinene (chemo-selectivity). Nonetheless, we were not able to achieve a stereo-selective epoxidation of the terpenes using alumina and hydrogen peroxide.
