Falloff curve and specific rate constants for the reaction NO2+NO2⇄N2O4 (original) (raw)

diones further supports this mechanistic hypothesis. Listed in are the ketones and diones for which we have recently determined the temperature dependence of OH reactivity along with an indication of the type of CH3 and/or CH2 groups responsible for reactivity. Clearly, for both acetone and 2,3-butanedione, where only LY components react, a positive activation energy of approximately 1 kcal/mol is observed. For 2-butanone and 3-pentanone, where reactivity (proceeding through formation of an adduct intermediate) accounts for almost 30% of the reaction rate (at room temperature), the activation energies drop to values much closer to zero. Finally, for 2,5-hexanedione, where the majority of the molecule's reactivity involves the @CHZ groups, a strong "negative activation energy" is calculated.