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Preparation of Carbon Nanosheets at Room Temperature
Published on: March 8, 2016
HCN polymers characterized by solid state NMR: chains and sheets formed in the neat liquid
Irena Mamajanov1, Judith Herzfeld
1Department of Chemistry, Brandeis University, Waltham, Massachusetts 02454-9110, USA.
The Journal of Chemical Physics
|April 10, 2009
Summary
Hydrogen cyanide polymers, crucial for prebiotic chemistry, are formed by simple monomer addition into 2D networks, not previously proposed structures. Solid-state NMR reveals these novel polymer structures, clarifying their formation pathways.
Area of Science:
- Astrochemistry
- Polymer Chemistry
- Organic Chemistry
Background:
- Hydrogen cyanide (HCN) polymers are significant in prebiotic chemistry due to HCN's cosmic abundance.
- Previous proposed structures for HCN polymers lacked strong experimental evidence.
- Understanding HCN polymer structure is key to understanding early life chemical pathways.
Purpose of the Study:
- To experimentally determine the structure of polymers formed from neat hydrogen cyanide.
- To reconcile existing data with new structural findings.
- To clarify the polymerization mechanism of hydrogen cyanide.
Main Methods:
- Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy using (13)C and (15)N isotopes.
- Analysis of polymers formed under neat HCN conditions.
- Comparison of experimental data with proposed polymer structures.
Main Results:
- Solid-state NMR spectra are inconsistent with previously suggested HCN polymer structures.
- Polymers form via sequential monomer addition: first head-to-tail (linear, conjugated chains), then laterally (saturated 2D networks).
- Free radicals support the proposed polymerization mechanism.
Conclusions:
- The structure of hydrogen cyanide polymers is a 2D network formed by simple monomer addition.
- This finding revises our understanding of HCN polymerization.
- Diaminomaleonitrile formation is limited to base-catalyzed, crystalline conditions.
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