Thermodynamics and Kinetics of Click Reaction between Benzyl Azide and Different Alkynes by Microcalorimetry

The copper(I)-catalyzed 1,3-dipolar cycloaddition of azides and alkynes provides diverse building blocks for chemical synthesis, biochemistry, pharmaceutical industries, and materials science. To provide a good theoretical support for industrial amplification reaction, it is significant to study the catalytic properties and the corresponding kinetics of a given reaction. In this article, the reaction kinetics and thermodynamics of "click reaction" between benzyl azide and different alkynes were investigated by microcalorimetry. Benzyl azide and ethyl propiolate were used as model reactions. The effects of a variety of parameters were studied in a calorimeter to establish the kinetics and mechanism of the reaction under isothermal conditions. The activation energies for the reaction of benzyl azide with 4-nitrophenylacetylene, ethyl propiolate, and 3-butyn-2-one were 22.99 ± 0.13, 55.81 ± 0.74, and 56.75 ± 0.65 kJ mol–1, respectively. The difference of reaction kinetics of different alkynes was explained by the reaction mechanism combined with theoretical calculations, and the reaction is intrinsically kinetically controlled.