SME
Organic Chemistry II · Problem type
Kinetic or thermodynamic enolate
Use this for “2-Methylcyclohexanone is treated with LDA in THF at −78 °C, then CH₃I. Which α carbon gets the new methyl?”
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Which enolate of 2-methylcyclohexanone do these conditions give?
Tap a card, then tap its group.
Strong, bulky base, cold and no proton source: the fastest one stays. Anything that lets protons move back: the most stable one.
Assumptions
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2-Methylcyclohexanone has two α carbons: C6 holds two hydrogens and no methyl, C2 holds one hydrogen and the methyl.
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The C6 hydrogens are less hindered, so a bulky base removes one faster: the less substituted (kinetic) enolate forms first.
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The enolate with the more substituted C=C is the more stable one, so it wins whenever the enolates can swap protons and reach equilibrium.
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Equilibrium needs some proton source: an alcohol solvent, leftover ketone, a weaker base or a long time warm.
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