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Topochemical Postulates: Are They Relevant for Topochemical Reactions Occurring at Elevated Temperatures?
Arthi Ravi1, Syed Zahid Hassan1,2, Subhrajyoti Bhandary1,3
1School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, 695551, Vithura, India.
Angewandte Chemie (International Ed. in English)
|March 8, 2022
Summary
Crystalline polymers formed unexpectedly from an inositol monomer. Heating induced molecular motion, enabling regiospecific azide-alkyne cycloaddition polymerization despite initial unfavorable crystal structures.
Area of Science:
- Polymer Chemistry
- Materials Science
- Crystallography
Background:
- Topochemical polymerization relies on reactant molecule orientation within crystal lattices.
- Predicting reactivity based solely on crystal structure can be challenging, especially under thermal conditions.
Purpose of the Study:
- To investigate the polymerization behavior of a rigid inositol-derived monomer with azide and alkyne functional groups.
- To explore the influence of crystalline polymorphs on topochemical polymerization reactions.
Main Methods:
- Synthesis of an inositol-derived monomer featuring azide and alkyne complementary reactive groups (CRGs).
- Crystallization of the monomer into three distinct polymorphs (I-III).
- Thermal analysis and characterization of the polymerization process and resulting polymer structures.
Main Results:
- Three distinct polymorphs of the monomer were obtained.
- Despite unfavorable CRG orientation, all polymorphs underwent quantitative and regiospecific topochemical azide-alkyne cycloaddition (TAAC) polymerization upon heating.
- Three different crystalline polymorphs of the resulting poly-neo-inositol were formed.
Conclusions:
- Monomers can overcome unfavorable crystal packing through thermally induced molecular motion to achieve polymerization.
- Crystal lattice dynamics and weak intermolecular forces play crucial roles in enabling topochemical reactions.
- Relying solely on static topochemical postulates for predicting high-temperature reactivity may be unreliable.
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