What made Arkema’s peroxides unstable?

Abstract

Organic peroxides, the chemicals that led to evacuations and explosions at the flooded Arkema chemical plant in Crosby, Texas, are well-known for their instability—the characteristic that provides both their chemical utility and their hazardous properties. Organic peroxides contain the peroxide functional group ROORʹ.The O–O bond is inherently weak; the bond dissociation energy of CH3O–OCH3 is 157.3 kJ/mol compared with 335 kJ/mol for CH3–OCH3. Exactly why O–O bonds are so weak is an “excellent question,” says Weston T. Borden, a computational chemist at the University of North Texas, “because I do not think that the correct answer is known with any degree of certainty.” Likely, the weak peroxide bond arises from repulsion between the lone pairs of electrons on the oxygen atoms, combined with the atoms’ high electronegativity, or tendency to attract electrons. “Covalent bond formation involves transfer of electron density to the region between the two atoms that are covalently