Identifying Chiral Centers in Testosterone Structure

Steps:

• Recall testosterone's steroid backbone: four fused rings (A, B, C, D) with methyl groups at C10 and C13, a hydroxyl at C17, and a ketone at C3.
• Locate tetrahedral carbons with four different substituents, focusing on ring junctions (C5, C8, C9, C10, C13, C14) and functional groups.
• Verify C8, C9, C10, C13, C14, and C17 as chiral (each has unique attachments); C5 is not due to planar double bond.
• Confirm no additional chirality in side chain or elsewhere, totaling six.

Why B is correct:

• Testosterone has exactly six asymmetric carbons, each with four distinct substituents per the definition of a chiral center.

Why the others are wrong:

• A: Misses the chiral center at C17 in the D-ring side chain.
• C: Incorrectly counts C5 as chiral, ignoring its sp2 hybridization from the double bond.
• D: Overcounts by including non-chiral carbons like those in methyl groups.

Final answer: B