The 1-phenylpropan-2-yl cation, $C X_{6} H X_{5} CH X_{2} - CH X^{+} - CH X_{3}$ , is formed in solution. Which cation is produced by a single 1,2-shift and is the most stable one accessible?

A1-phenylpropyl cation, $C X_{6} H X_{5} - CH X^{+} - CH X_{2} CH X_{3}$ , by a 1,2-hydride shift
B2-phenylpropyl cation, a primary cation, by a 1,2-hydride shift
C2-phenylpropan-2-yl cation, $C X_{6} H X_{5} - C X^{+} (CH X_{3}) X_{2}$ , by a 1,2-methyl shift
Dno shift is favourable because the starting cation is already benzylic

Answer: A

The starting cation is secondary and not benzylic. A hydride from the benzylic

CH X_{2}

moves to the cationic carbon, which puts the charge on the benzylic carbon (resonance with the ring). The 2-phenylpropan-2-yl cation cannot form in one step since it needs a different carbon connectivity.

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The 1-phenylpropan-2-yl cation, CX6​HX5​CHX2​−CHX+−CHX3​, is formed in solution. Which cation is produced by a single 1,2-shift and is the most stable one accessible?

Answer: A

More questions on Carbocations: formation, stability, rearrangements

The 1-phenylpropan-2-yl cation, $C X_{6} H X_{5} CH X_{2} - CH X^{+} - CH X_{3}$ , is formed in solution. Which cation is produced by a single 1,2-shift and is the most stable one accessible?