Q.A. Write condensed formulae and bond line formulae for the following structures.
a. H-C-C-C-C-H, a straight four-carbon chain with all hydrogens shown on every carbon.
b. N≡C-C-C-C≡N, a four-carbon chain with a C≡N group at each end and H,H shown on each of the two middle carbons.
c. H-C-C-C-C(=O)-OH, a four-carbon chain with H atoms shown on the first three carbons and a terminal carboxylic acid group.

Step 1. Count carbons and read off substituents in each dash formula.

a. Four carbons in a straight chain, every carbon carrying only H's: this is n-butane.

b. Four carbons in a straight chain, a C≡N group at each end, H,H on each of the two middle carbons: this is butanedinitrile (succinonitrile).

c. Four carbons in a straight chain, H's on the first three carbons, a C(=O)OH group on the fourth: this is butanoic acid.

Step 2. Write the condensed formula by folding each carbon's identical attached hydrogens into a subscript, keeping any heteroatom-bearing group written out in full.

a. CH3-CH2-CH2-CH3, or CH3(CH2)2CH3.

b. NC-CH2-CH2-CN.

c. CH3-CH2-CH2-COOH.

Step 3. Write the bond-line (zig-zag) formula, following section 14.2.2's convention: drop the C and H symbols entirely for the plain carbon-chain part (each zig-zag terminus reads as CH3, each internal vertex as CH2), but write out any heteroatom-bearing group explicitly since heteroatoms are never hidden.

a. A butane chain has 3 C-C bonds, so this is a 3-segment zig-zag line with nothing else to write (both ends are plain CH3).

b. The two end carbons are C≡N groups (heteroatom-bearing), so only the two internal CH2-CH2 carbons are drawn as the zig-zag line (1 segment), with 'N≡C-' written explicitly at each end.

c. The COOH carbon is a heteroatom-bearing (carbonyl + OH) group, so it is written out explicitly, while the CH3-CH2-CH2- part before it is a 2-segment zig-zag line.

Reading each dash formula for its carbon count and substituents, then applying section 14.2.1's condensed-formula convention and section 14.2.2's bond-line convention in turn

• Trying to hide the heteroatom-bearing groups (COOH, C≡N) in the zig-zag formula the same way plain carbons are hidden; the chapter's own convention keeps these written out explicitly.
• Miscounting the zig-zag segment count (segments = number of C-C bonds actually being represented as the plain chain, not the total carbon count of the molecule).