Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA.
J Am Chem Soc. 2013 May 1;135(17):6626-32. doi: 10.1021/ja401577p. Epub 2013 Apr 17.
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 (13)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.
具有大体积取代基的结晶三唑啉的光诱导和热脱氮导致在清洁的固-固反应中定量形成氮丙啶，尽管在反应物到产物的转变过程中发生了非常大的结构变化。通过粉末 X 射线衍射、固态 (13)C CPMAS NMR、固态傅里叶变换红外光谱和热分析对反应进展进行分析表明，固-固反应要么通过易非晶化的亚稳相进行，要么通过涉及重建相转变的机制进行，最终形成产物的稳定相。虽然固-固转化的关键是反应发生在反应物和产物双组分系统的共晶温度以下，但实验证据表明，当反应发生在玻璃化转变温度以上时，这些反应将经历重建相转变。
