OChem Ch 4 The Study of Chemical Reactions

  1. what does it mean when a molecule like Cl2 is split homolytically?
    each atom gets one electron from the bonding electrons
  2. what does it mean when a molecule like Cl2 is split heterolytically?
    one atom gets both bonding electrons
  3. What are the three steps of the free radical chain reaction?
    initiation, propogation, and termination
  4. what occurs during the termination step?
    the collision of ANY two free radicals.
  5. what is the relationship between bond dissociation enthalpies and bond breaking/formation?
    bond breaking requires energy (+BDE). bond forming releases energy (-BDE)
  6. what does kinetics have to deal with?
    how fast a reaction goes
  7. For A + B --> C + D, what is the rate law and annotate all of the variables.
    rate = k[A]a[B]b

    where k is a constant, and the exponents are the order in respect to each reactant.
  8. what is rate order
    the order is the number of molecules of that reactant which is present in the rate-determining step of the mechanism
  9. activation energy
    minimum energy required to reach the transition state
  10. how do you determine the rate-determining step of a reaction?
    the reaction step with highest Ea wil be the slowest.
  11. what is the order of stability for alkyl free radicals in halogenation?

    so it's easiest to remove H from 3° and least for methyl
  12. what are the four reactive intermediates?
    carbocations, free radicals, carbanions, carbenes
  13. carbocation
    carbon has 6 electrons, and positive charge. sp2 hybridized and one empty p orbital.
  14. What is carbocation order of stability?

    so, this molecule is the most stable cation:

    •                  CH3
    •                    |
    •             CH3-C (+)
    •                    |
    •                  CH3
  15. what are the two ways that a carbocation is is stabilized by alkyl substituents?
    1) Inductive effect: donation of electron density along the sigma bonds

    2) hyperconjugation: overlap of sigma bonding orbitals with empty p orbital
  16. free radical
    carbon has one odd electron and is bonded to three substituents. Order of stability: 3°>2°>1°>methyl
  17. carbanions
    eight electrons on Carbon (6 bonding and 1 lone pair). carbon has a negative charge. Destabilized by alkyl substituents. order of stability: methyl>1°>2°>3°
  18. carbene
    carbon is neutral. vacant p orbital, so can be electrophilic. lone pair of electrons, so can be nucleophilic. and two substituents
Card Set
OChem Ch 4 The Study of Chemical Reactions
OChem Ch 4 The Study of Chemical Reactions