Photoinduced and Thermal Denitrogenation of Bulky
Triazoline Crystals: Insights into Solid-to-Solid Transformation
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Abstract
The
photoinduced and thermal denitrogenation of crystalline triazolines
with bulky substituents leads to the quantitative formation of aziridines
in clean solid-to-solid reactions despite very large structural changes
in the transition from reactant to product. Analysis of the reaction
progress by powder X-ray diffraction, solid-state <sup>13</sup>C CPMAS
NMR, solid-state FTIR spectroscopy, and thermal analysis has revealed
that solid-to-solid reactions proceed either through metastable phases
susceptible to amorphization or by mechanisms that involve a reconstructive
phase transition that culminates in the formation of the stable phase
of the product. While the key for a solid-to-solid transformation
is that the reaction occurs below the eutectic temperature of the
reactant and product two-component system, experimental evidence suggests
that those reactions will undergo a reconstructive phase transition
when they take place above the glass transition temperature