Kinetics of a pressure-induced polymerization reaction of cyanogen

Abstract

The kinetics of the conversion of poly-(2,3-diiminosuccinonitrile), a polymeric high pressure form of cyanogen, to paracyanogen have been determined by monitoring Fourier-transform infrared spectra at pressures between 10 and 12 GPa and temperatures between 290 and 350 K. The reaction kinetics can be described by an Avrami equation with exponent, 0.5, and specific rate constant, 0.040 h~1/2, at 10 GPa and 297 K. The activation enthalpy and volume are 28 kJ/mol and -3.3 cm1 23/mol, respectively. A two-step mechanism is suggested that involves diffusive rearrangement of the p-DISN chains into a configuration in which 4 + 2 cycloadditions occur between adjacent p-DISN chains.

Elementary Reactions of Nitrogen and Oxygen with Boron and Carbon at High Pressures and Tempeatures.

“…In contrast, the network structure is ubiquitous at high pressures, as unsaturated chemical bonds become unstable at high pressures with respect to associative, cross-linking reactions forming denser, more saturated species [1]. This is because at high pressure the kinetic energy of electrons dominates and the intermolecular interaction of isolated molecules becomes mostly repulsive in nature.…”

“…The examples of endothermic reactions include copolymerization of diatomic molecules [1,2], hydride forming reactions, and metallization [3] at high pressures. The latter type, on the other hand, includes the reactions forming various nitrides, oxides, and carbides.…”

High-pressure photodissociation of water as a tool for hydrogen synthesis and fundamental chemistry

“…Upon further compression, the possible overlap of the electronic density of nearest-neighbor molecules can also trigger a complete reconstruction of the chemical bonds, giving rise to new materials in some cases recoverable at ambient conditions (2). After the pioneering work on the pressure-induced polymerization of cyanogen (3) and acetylene (4) crystals, several simple molecular crystals have been reported to react upon application of suitable external pressure, giving rise to high-quality polymeric (5-7) and amorphous (8-10) materials of potential technological interest. These transformations require pressures from several to 100 GPa, as in the nitrogen case (7), but the reaction threshold pressure has been successfully lowered in almost all of the unsaturated hydrocarbons studied so far by a photoactivation of the high-pressure reactions (11).…”

IR Study of the Pressure Induced Solid State DI- and Polymerization in 1,3-butadiene

“…In particular, solid state reactions can proceed in crystal phases where molecules have fixed positions. In these conditions relative molecular orientations and intermolecular distances can drive the reaction along completely different paths with respect to those observed at ambient conditions [1,2,3]. Butadiene is a very interesting reacting system.…”