Chemistry · Covalent bond fission: Homolytic and heterolytic, free radicals, carbocations and carbanions, stability of carbocations and free radicals, electrophiles and nucleophiles

The first transition state in the overall exothermic addition of HBr to propane

The first transition state in the overall exothermic addition of HBr to propane resembles the intermediate (carbocation). Choose the best phrase to complete the following statement The second transition states (for addition of \( B r^{-} \) to the carbocation):

  • A. resembles the final product
  • B. resembles the 2-propyl cation
  • C. resembles propene
  • D. has all carbons almost entirely sp \( ^{3} \) hybridized

Step-by-step solution

The second step (addition of Br- to the carbocation) is exothermic. According to the Hammond postulate, the transition state for an exothermic step resembles the reactants, which is the 2-propyl cation. Thus, the second transition state resembles the carbocation intermediate.
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