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Cyclic anhydride ring opening reactions: theory and application
J K West1, A B Brennan, A E Clark
1Department of Materials Science and Engineering, University of Florida, Gainesville 32611-6400, USA.
Journal of Biomedical Materials Research
|June 26, 1998
Summary
This study investigated organic cyclic anhydrides for dental materials. Researchers found that hydrolysis causes ring expansion, with specific anhydrides showing significant volumetric changes, offering potential for zero net shrinkage composites.
Area of Science:
- Materials Science
- Computational Chemistry
- Polymer Chemistry
Background:
- Developing dental restorative materials with zero net shrinkage is crucial.
- Polymer-bioactive-glass composites require an expanding second phase to counteract shrinkage.
- Organic cyclic anhydrides are investigated as potential expanding agents.
Purpose of the Study:
- To detail the mechanisms of organic cyclic anhydride ring expansion via hydrolysis.
- To model and compare the expansion potential of six different cyclic anhydrides.
- To establish a correlation between molecular vibrations and reactivity for predicting expansion.
Main Methods:
- Semi-empirical molecular orbital calculations (Austin Method AM1) were used.
- Reaction pathways and activation energies (Ea) for anhydride ring opening were determined.
- Volumetric expansion was estimated by analyzing changes in C-O-C bond distances.
Main Results:
- Hydrolysis involves water molecule interaction, C-O bond weakening, and ring opening to form dicarboxylic acids.
- Activation energies for ring opening ranged from +34.3 to +47.7 kcal/mol.
- Estimated volumetric expansion varied from 17.9% to 24.0% for the studied anhydrides.
Conclusions:
- Organic cyclic anhydrides can expand via hydrolysis, making them suitable for zero net shrinkage dental materials.
- A linear correlation was found between the C-O asymmetric rocking vibration and activation energy, serving as an experimental predictor of anhydride activity.