Q.

1. Phytane is a naturally occurring alkane produced by the alga spirogyra and is a constituent of petroleum. The IUPAC name for phytane is 2,6,10,14-tetramethylhexadecane. Write zig-zag formula for phytane. How many primary, secondary, tertiary and quaternary carbons are present in this molecule.

Step 1. Build the structure from the name. Parent = hexadecane, a straight 16-carbon chain (C1-C16); four methyl substituents, at C2, C6, C10, and C14 -- a regular, evenly-spaced (isoprenoid-type) branching pattern. Zig-zag formula: a 16-vertex zig-zag main chain, with one short methyl branch drawn off vertices 2, 6, 10, and 14.

Step 2. Classify every carbon (section 14.4.1's primary/secondary/tertiary/quaternary scheme).

• C1 and C16 (the two chain termini): each bonded to only 1 other carbon -> primary. That is 2 primary carbons.
• The 4 methyl branches (on C2, C6, C10, C14): each bonded to only its own attachment carbon -> primary. That is 4 more primary carbons. Total primary = 2 + 4 = 6.
• C2, C6, C10, C14 (the branch-bearing chain carbons): each bonded to 2 chain neighbours PLUS its own methyl branch = 3 other carbons -> tertiary. Total tertiary = 4. …

Rebuilding the structure directly from the given IUPAC name (2,6,10,14-tetramethylhexadecane), then classifying every one of its …

• Miscounting the main-chain length (hexadecane = 16 carbons, not 14 or 15).
• Forgetting to count the 4 branch (methyl) carbons themselves as primary carbon …