Question:medium

Predict the alkene that would be formed by dehydrohalogenation of 1-Bromo-1-methylcyclohexane.

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Internal double bonds are generally more stable than terminal/exocyclic ones due to more hyperconjugative stabilization.
Updated On: Jul 23, 2026
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Solution and Explanation

Step 1: Locate the available beta-hydrogens.
In 1-bromo-1-methylcyclohexane, the bromine and a methyl group both sit on carbon 1 of the ring. For elimination we need a hydrogen on a carbon next door, and there are two different sets available, the hydrogens on the methyl group itself, and the ring hydrogens on carbons 2 and 6.
Step 2: Write out the two possible alkenes.
Removing a hydrogen from the methyl group would put the double bond outside the ring, giving methylenecyclohexane. Removing a hydrogen from carbon 2 or 6 instead keeps the double bond inside the ring, giving 1-methylcyclohexene.
Step 3: Decide which one wins using Zaitsev's rule.
Zaitsev's rule favours the alkene with more alkyl substitution on its double bond carbons, since a more substituted double bond is more stable. 1-methylcyclohexene has three alkyl groups on its double bond carbons, trisubstituted, while methylenecyclohexane has only two, disubstituted.
Step 4: Conclude.
Being the more substituted, more stable alkene, 1-methylcyclohexene forms as the major product.
\[ \boxed{\text{1-methylcyclohexene}} \]
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