Macrocyclic geminal diols: synthesis, structures, stability and photophysical properties
Bo Zou1, Xiaolin Chen1, Haoran Liu1
1School of Chemistry, South China Normal University Guangzhou 510006 China fanj@scnu.edu.cn hwjiang@m.scnu.edu.cn.
Chemical Science
|November 21, 2025
Summary
Researchers synthesized stable macrocyclic geminal diols (compounds with two hydroxyl groups on the same carbon) by hydrolyzing ketals. Smaller ring sizes and specific bond angles enhance gem-diol stability.
Area of Science:
- Organic Chemistry
- Supramolecular Chemistry
- Chemical Crystallography
Background:
- Geminal diols are typically unstable and difficult to isolate due to facile dehydration to carbonyl compounds.
- Macrocyclic compounds offer unique structural rigidity and potential for stabilizing unusual functional groups.
Purpose of the Study:
- To synthesize and characterize stable macrocyclic geminal diols.
- To investigate the factors influencing the stability of these geminal diols.
- To explore the structure-stability relationships and potential applications of macrocyclic geminal diols.
Main Methods:
- Synthesis of macrocyclic geminal diols via acid hydrolysis of macrocyclic ketals at low temperatures (-25 °C).
- Structural characterization using single-crystal X-ray diffraction.
- Stability assessment through thermogravimetric and hydrolytic analyses.
- Computational modeling (theoretical calculations) to understand stability factors.
Main Results:
- Successfully synthesized and isolated crystalline, stable macrocyclic geminal diols.
- X-ray diffraction revealed specific O-C-O bond angles (~111°) and extensive hydrogen-bonding networks contributing to stability.
- Stability was found to be size-dependent, with smaller macrocycles exhibiting enhanced stability.
- Theoretical calculations correlated stability with angle strain relief via sp³ hybridization at the methylene carbon.
Conclusions:
- The stability of macrocyclic geminal diols is influenced by ring size and internal bond angles.
- The inner angle of the precursor macrocyclic ketone can serve as a predictor for geminal diol stability.
- This study expands the known chemistry of geminal diols and provides a foundation for designing novel macrocyclic structures.
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