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You are using Science Of Synthesis as a Guest. Please login or sign up for a free trial to access the full content. Method 1: Acid-Catalyzed Dehydration

DOI: 10.1055/sos-SD-037-00438

Robina, I.; Vogel, P.Science of Synthesis, (200837655.

In 2M hydrochloric or sulfuric acid, pentitols eliminate 1 equivalent of water, producing 1,4- and 2,5-anhydropentitols (Scheme 11). The dehydration of alditols in acidic media is believed to involve SNi displacements of a protonated hydroxy group by an alcoholic moiety. The rate of the reaction is influenced by the environment of the leaving group and of the nucleophile, as well as by the orientation of the hydroxy groups not directly involved in the reaction. Inversion of configuration can occur at C2 or C4 during the 1,4- and 2,5-anhydride formation but no inversion at C3 has been observed.[‌50‌] The relative rate of the dehydration reaction decreases in the order ribitol > xylitol > arabinitol (lyxitol).

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