| Popis: |
Base-catalyzed intramolecular nucleophilic substitution of various dianhydrosorbitol derivatives (2, 4, or 6) led to formation of trianhydromannitol (7), a tricyclic system of three interlinked oxolane rings. By treatment with trifluoromethanesulfonic acid, ring-opening reactions were achieved to give oligomeric soluble material with a number-average degree of polymerization Molecular weights were determined by GPC, and by desorptive chemical ionization (DCI) with ammonia a molecular weight assignment gave information on the degree of crosslinking. A complex but consistent picture allows to explain the propagation reactions of protonated trianhydromannitols 8 and 9, and further reactions of the protonated intermediates 13–15 to result in crosslinked products 16 and 17. By semiempirical quantum chemical calculations, geometries, energies and charge distributions of 7 as well as its protonated species were obtained. This allowed comparisons with their chemical reactivity and ring-opening specificity. |
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