The second-order reactions in Table 7D.1 show wide variations in activation energy. In an activated complex, the reactant bonds are lengthened while the product bonds are beginning to form. Consider what bonds need to be stretched to form the activated complex for each reaction and use bond enthalpies to explain the differences in activation energies.

Transcribed Image Text:

TABLE 7D.1 Arrhenius Parameters Reaction First order, gas phase cyclopropane propene CH3NC CH3CN C₂H62 CH3 N₂ + O N₂O 2 N₂O5 4 NO₂ + O₂ Second order, gas phase O + N₂ NO + N OH + H₂ →→→ H₂O + H 2 CH3 →→ C₂H6 Second order, in aqueous solution C₂H,Br + OHC₂H₂OH + Br CO₂+ OH-→→→ HCO, C12H₂2011 + H₂O2 CH₁2O6 A 1.6 x 10¹5 S-1 4.0 × 10¹3 S-1 2.5 x 10¹7 S-1 8.0 x 10¹¹ S-1 4.0 × 10¹3 S-¹ 1x 10¹¹ L-mol ¹.s¹ 8 x 100 L-mol ¹.S¹ 2 X 100 L-mol-¹.s-1 4.3 X 10¹¹ L.mol-¹s-¹ 1.5 x 10¹0 L-mol-¹.s-¹ 1.5 x 10¹5 L-mol-¹.s-¹ E₂/(kJ-mol-¹) 272 160 384 250 103 315 42 0 90 38 108