Synthesis and ring‐opening polymerization of 1,4:2,5:3,6‐trianhydro‐ D ‐mannitol and structure studies by MNDO calculations

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 {article}{empty}{document}DP̄ ₙ ≈ 5 - 10{document} 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.