Allylic Carbocations
Practice
1.
Classify the following carbocations from the least to most stable:
Answer
2.
When the solution of the following bromide is heated up in ethanol, eight products (excluding the elimination reactions) are formed.
Draw plausible mechanisms to explain the formation of these isomers.
Answer
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Can you provide detailed explanation
Isn´t the Allylic Carbocation more stable than the methyl-cyclohexane (f) because of the resonance stabilisation? And why is compound a more stable than d?
You are right, but you might be looking in the wrong direction – the ones on the right are more stable.
Could you please explain why f) is more stable than b).
Thanks for your quick response
One argument is that although it is allylic, the charge is still delocalized over primary carbon atoms. Allylic itself does not mean it is more stable than any other carbocation. I mean you don’t need to memorize how stability of each combination of allylic copares to any secondary or tertiary carbocation. Focus rather on the general patterns unless you are asked to expicitly knwo their stabilty. There are some practice problems you can also work on here: https://www.chemistrysteps.com/stability-of-carbocations/