Thermally Annealed Solid State Polymerization of 2,3-Dicyano-5,7-Dimethyl-6H-1,4-Diazepine: An NMR Study

ABSTRACT

The thermally annealed solid state polymerization of 2,3-dicyano-5,7-dimethyl-6H-1,4-diazepine( A) was studied by ¹H, ¹³C, and ¹⁵N CP/MAS solid state NMR spectroscopy, and by a ¹H solution state NMR deuterium exchange experiment of A. Collectively, the NMR data suggests that a tautomeric form of the monomer is responsible for the solid state reactivity of the crystalline monomer. The solid state polymerization of crystalline A proceeds as a heterogeneous decomposition of the crystalline lattice resulting in an insoluble, amorphous material. A plausible reaction scheme involving a tautomeric form of A is proposed. The scheme is consistent with the NMR spectra.

Keywords:

• ¹³C NMR spectroscopy
• deuterium exchange
• diazepine
• ¹H NMR spectroscopy
• ¹⁵N NMR spectroscopy
• solid state polymerization

Acknowledgments

This work was supported in part by the Petroleum Research Fund Grant 37138-AC1. The Bruker DMX spectrometer was purchased in part with funds supplied by the National Science Foundation. The authors thank Professor Bruce M. Foxman for useful discussions.