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Review

. . Review. Reaction mechanism. . C 5 H 11 Br (l). + HBr (l). Br 2 (l). + C 5 H 12 (l). h . 2 Br. step 1. Br 2. C 5 H 12 . step 2. Br . +. HBr + C 5 H 11. C 5 H 11 . +. Br . . C 5 H 11 Br. step 3. overall. Br 2. . C 5 H 11 Br. + HBr. + C 5 H 12. . .

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Review

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  1.  Review Reaction mechanism  C5H11Br(l) + HBr(l) Br2(l) + C5H12(l) h 2 Br. step 1 Br2 C5H12 step 2 Br. + HBr + C5H11. C5H11. + Br.  C5H11Br step 3 overall Br2  C5H11Br + HBr + C5H12

  2.  Br2(l) + C5H12(l) C5H11Br(l) + HBr(l) h 2 Br. step 1 Br2 C5H12 step 2 Br. + HBr + C5H11.  step 3 C5H11. + Br. C5H11Br assumestep 2 is rate determining (slow) rate = k2 [Br.] [C5H12] Br.= intermediate [Br.]2 [Br2] Keq = rate = k2 k’[Br2]1/2 [C5H12] rate = k’[Br2]1/2 [C5H12] [Br.] = Keq1/2 [Br2]1/2 11/2 order reaction

  3. bimolecular elementary steps increase [react]  increase rate of reaction increase T  increase rate of reaction increase number of collisions increase force of collisions

  4. T2 Ea T1 T2 > T1 # molecules Kinetic Energy minimum energy required for reaction: activation energy = Ea

  5. Arrhenius Equation T dependence of a rate constant, k k = z p e-Ea/RT k a) increases b) decreases with T with Ea k a) decreases b) increases Ea = activation energy (kJ/mol) R = gas constant (8.314 x 10-3kJ/K mol) T = temperature (K) z = collision frequency p = steric factor (<1)

  6. p = steric factor z = collision frequency combine to give A A k = e-Ea/RT

  7. Arrhenius Equation k = A e-Ea/RT - (Ea/R) (1/T) ln k = - (Ea/R) (1/T) + ln A ln A y = m x + b plot ln k v.s. 1/T slope = -Ea/R intercept = ln A - 1/T2) ln (k2/ k1) = (Ea /R) (1/T1

  8. A-B + C A...B...C activated complex P.E. is at a maximum transition state A + B-C

  9. activated complex Eaf Eab reactants P.E. Hrxn products Reaction coordinate A-B + C A...B...C A + B-C

  10. activated complex Eaf Eab reactants P.E. Hrxn products Reaction coordinate exothermic Eab Eaf > endothermic

  11. Eab Eaf reactants products activated complex P.E. Reaction coordinate exothermic Eab Eaf > large Ea = slow rate endothermic Eab Eaf <

  12. - catalyst + catalyst lowers Eaf faster forward reaction ( kf ) lowers Ear faster reverse reaction ( kr ) kf and H Keq unchanged Keq = kr

  13. Br2 + C5H12 P.E. C5H11Br + HBr Reaction coordinate Br2(l) + C5H12(l) C5H11Br(l) + HBr(l) Hrxn < 0 Ea Hrxn

  14. hn 2 Br. h step 1 Br2 C5H12 step 2 Br. + HBr + C5H11. step 3 C5H11. + Br.  C5H11Br Br2(l) + C5H12(l) C5H11Br(l) + HBr(l) Ea Ea Ea HBr + C5H11. + Br. 2Br. + C5H12 C5H12 + Br2 P.E. C5H11Br + HBr

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