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QLDChemistryQuick questions
Unit 4: Structure, synthesis and design
Quick questions on IUPAC nomenclature and functional groups (QCE Chemistry Unit 4)
15short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is the ten homologous series?Show answer
QCAA past papers expect you to identify any of these from a structural formula and to write the matching name and formula on demand.
What is naming rules in priority order?Show answer
1. Identify the principal functional group (highest in the suffix priority list). Order from highest to lowest: carboxylic acid, ester, amide, aldehyde, ketone, alcohol, amine, alkene, alkane. Haloalkanes are always prefixes, never suffixes.
What is worked names?Show answer
CH3-CH(OH)-CH2-CH3. Principal group: -OH (alcohol). Longest chain containing it: 4 carbons. Number so OH gets the lowest locant: from the left, OH is on C2; from the right, OH is on C3. Use C2.
What is structural-formula conventions?Show answer
QCAA accepts three structural-formula styles:
What is common nomenclature traps?Show answer
Numbering from the wrong end. Always number so the principal suffix gets the lowest locant. Substituents come second in the tie-breaker.
What is why this matters in IA3 and the EA?Show answer
IA3 research investigations frequently include comparisons of compounds named by functional group (esters in flavour chemistry, polymers built from specific monomers). The EA Paper 1 multiple choice typically includes one or two nomenclature items, and Paper 2 short response routinely asks students to draw structures from names or vice versa. Errors here propagate into every downstream answer about reactivity or spectroscopy.
What is cH3-CH -CH2-CH3?Show answer
Principal group: -OH (alcohol). Longest chain containing it: 4 carbons. Number so OH gets the lowest locant: from the left, OH is on C2; from the right, OH is on C3.
What is 2CH-CH2-CH2-COOH?Show answer
Principal group: -COOH (highest priority). Longest chain containing COOH: 5 carbons (pentanoic acid). COOH carbon is C1.
What is cH3-CH2-O-CO-CH3?Show answer
Two oxygens between the ester carbon and the next chain identify this as an ester. The acid side (with C=O) is ethanoic; the alcohol side (CH3CH2-) is ethyl. Esters are named alcohol-side first as the alkyl, acid-side second as the -oate.
What is cH3-CO-NH-CH3?Show answer
Amide. Parent is the acid chain bearing C=O (ethan-: 2 carbons). The nitrogen has one methyl substituent, prefixed with "N-" in italics.
What is numbering from the wrong end?Show answer
Always number so the principal suffix gets the lowest locant. Substituents come second in the tie-breaker.
What is forgetting locants on the suffix?Show answer
"But-2-ene" and "but-1-ene" are different compounds; "butan-2-ol" and "butan-1-ol" are different compounds. The locant goes immediately before the suffix.
What is naming esters backwards?Show answer
The alkyl group is from the alcohol; the -oate name is from the acid. Methyl propanoate is the ester of propanoic acid with methanol (CH3CH2COOCH3), not vice versa.
What is treating amines like amides?Show answer
An amine has C-NH2 with no carbonyl. An amide has C(=O)-NH2. Different functional groups, different reactivity, different IUPAC class.
What is confusing aldehyde and ketone numbering?Show answer
Aldehyde CHO is always on C1 (and the "1" is omitted). Ketone C=O is always internal and needs an explicit locant (butan-2-one, pentan-3-one).