You are shown a verbal description of a skeletal fatty-acid fragment: 'a zigzag with five vertices and a terminal carboxyl drawn at the rightmost end.' Explain how many carbons are present in the hydrocarbon chain portion (excluding the carboxyl carbon) and how many implicit hydrogens would a fully saturated version have attached to those internal carbons (total H on the chain carbons only, ignoring COOH H/O).

• A. Five carbons in the chain and 11 hydrogens on those carbons when fully saturated (excluding COOH hydrogens/oxygens).
• B. Five carbons and 15 hydrogens because each carbon always has three hydrogens in skeletal formulas.
• C. Four carbons and 10 hydrogens because the vertex nearest COOH does not count as carbon in skeletal formulas.
• D. Six carbons and 12 hydrogens because you must include the carboxyl carbon as part of the zigzag chain count.

Answer: (A)