III.  Chlorination of Higher Alkanes
     A.  Ethane - only one monochlorinated product - This and all other alkanes undergo the Official 
mechanism.
     B.  Propane 
          1.  Product Distribution: two monochlorinated products formed  namely 1-		
	chloropropane (40%)  and 2-chloropropane (60%)
          2.  Calculation of reactivity of primary and secondary H atoms
                                     % yield (secondary product) = reactivity per IIoH
                                       # of IIo H
                                   % yield (primary product)  = reactivity per IoH
                                     # of IoH
                                       60% / 2 IIoH =  30% per IIoH
                                       40%  / 6 IoH  =  6.7% per IoH

          3.  Calculation of relative reactivities:        
          sec H is abstracted 30/6.7 or 4.5 faster than a prim H.
          4.  Determination of radical stabilities from BDE (bond dissociation energies)
               tert radicals are more stable than sec radicals which are more stable than  primary radicals.
          5.  Comparison of energetics of the RDS (rate determining step) of the two 	
               competing radical reactions of propane - propane -->  propyl radical = 98 kcal
                    propane ---------> isopropyl radical = 95 kcal
                    note that the formation of the isopropyl radical is more exothermic than that  of the 
                    propyl radical.
          6. Energy vs. reaction path diagram: note that the more stable radical is more readily formed.
formed.
     C.  Isobutane (2-methylpropane)
          1. Product Distribution
               t-butyl chloride (38%) and isobutyl chloride (62%)
          2.  Calculation of reactivities of tertiary H vs. primary -you do the calculations.
          3. Relative reactivities of tert H vs. Prim H
                     t-butyl radicals are 5.5 times more reactive than primary.
     D.  Generalization - chlorination will give a single monochlorinated product if the hydrocarbon 
can give only one monochlorinated product:  these include methane, ethane, unsubstituted 
cycloalkanes and 2,2,3,3,tetramethylbutane and other permethylated hydrocarbons.
          Chlorination will give mixtures of products when two or more isomeric monohaloalkanes 
are possible.
IV.  Bromination of Propane
     A.  Product distribution
          isopropyl bromide (97%) and n-propyl bromide (3%)
     B.  relative reactivity of secondary H toward bromine is 97 X that of primary H 
             thus, bromine is more selective than chlorine
     C.  Energetics of the two competing bromination steps
                    The only additional  BDE need is that for HBr which is 88 kcal/mol
     D. Comparison of Energy vs. Reaction Path curves for Br2 and Cl2
          1.  one sees a much larger difference in activation  energies and alkyl radical products 
          2.  The bromination proceeds through a late transition state (more CH bond breaking)
             thus  transition state resembles radical intermediate
          3.   Chlorination proceeds through an early transition state (less CH bond breaking) thus 
             transition state resembles reactant.
          4.  Bromination is the method of choice for preparing alkyl halides from alkane that can give 
               two or more different isomeric alkyl halides.