Question

Which of the following hydrocarbons reacts easily with MeMgBr to give methane?

• A.
• B.
• C.
• D.

Hint:

Using a simple frame or just bolding for the box Key Points: Grignard reagents (like MeMgBr) are strong bases. They react with acidic protons (H$^+$) to form alkanes (methane in this case). Acidity of C-H bonds is determined by the stability of the resulting carbanion (conjugate base). Aromatic stabilization significantly increases the acidity of precursor C-H bonds. Cyclopentadiene's CH$_2$ protons are acidic (pKa $\approx$ 16) because the cyclopentadienyl anion is aromatic.