LiAlH4 reduces 1,2-diketones to vicinal diols Steps:

• The product, 4-methylpentane-2,3-diol, is a vicinal diol with OH groups on adjacent carbons 2 and 3.
• LiAlH4 selectively reduces ketones to secondary alcohols without affecting other functional groups.
• A vicinal diol forms from reduction of a 1,2-diketone, where both carbonyls become OH groups.
• Thus, compound R is 4-methylpentane-2,3-dione, matching the carbon skeleton and positions.

Why A is correct:

• Option A is 4-methylpentane-2,3-dione, the exact 1,2-diketone that reduces to the given diol via two ketone-to-alcohol conversions.

Why the others are wrong:

• B: A single ketone reduces to a monoalcohol, not a diol.
• C: Ester groups reduce to alcohols but yield different chain lengths or primary alcohols.
• D: Aldehyde-ketone mix produces a primary-secondary diol, mismatched to the product's secondary-secondary pattern.

Final answer: A