The diaxial conformer of trans-1-chloro-2-methylcyclohexane (Cl and $CH X_{3}$ both axial) is the reactive conformer for E2. How many beta C-H bonds in this conformer are anti-periplanar to the C-Cl bond? (Beta-hydrogens are those on the ring carbons adjacent to the C-Cl carbon.)

Answer: C

The beta carbons are C2 and C6. On C2 the methyl is axial (trans-diaxial to Cl), so its H is equatorial and not anti to Cl. On C6 one H is axial and trans to Cl, so it is anti-periplanar. The count is 1, and this H gives 3-methylcyclohexene.

Practice Organic Reaction Mechanisms IV: Elimination More on E2 mechanism and anti-periplanar requirement

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The diaxial conformer of trans-1-chloro-2-methylcyclohexane (Cl and CHX3​ both axial) is the reactive conformer for E2. How many beta C-H bonds in this conformer are anti-periplanar to the C-Cl bond? (Beta-hydrogens are those on the ring carbons adjacent to the C-Cl carbon.)

Answer: C

More questions on E2 mechanism and anti-periplanar requirement

The diaxial conformer of trans-1-chloro-2-methylcyclohexane (Cl and $CH X_{3}$ both axial) is the reactive conformer for E2. How many beta C-H bonds in this conformer are anti-periplanar to the C-Cl bond? (Beta-hydrogens are those on the ring carbons adjacent to the C-Cl carbon.)