Covers Lessons 1–4: Organic Chemistry Introduction, IUPAC Nomenclature, functional group classes, and structural isomers.
1. What is the correct IUPAC name for CH₃CH₂CH(OH)CH₂CH₃?
2. Which statement correctly classifies 2-methylbutan-2-ol?
3. A compound has formula C₄H₈O and gives a silver mirror with Tollens' reagent. What is the correct IUPAC name?
4. Which pair represents functional group isomers?
5. What is the correct IUPAC name for the ester CH₃CH₂COOCH₂CH₂CH₃?
MC Answers: 1-B | 2-C | 3-B | 4-C | 5-C
MC Explanations:
1-B: –OH is on C3 of a 5-carbon chain. Numbering from either end gives C3 → pentan-3-ol. Pentan-2-ol would have –OH on C2.
2-C: Structure = CH₃C(OH)(CH₃)CH₂CH₃. The C–OH carbon (C2) is bonded to three other carbons → tertiary.
3-B: Tollens' silver mirror = aldehyde only. C₄H₈O with aldehyde → butanal. Butan-2-one is a ketone (negative Tollens').
4-C: Butanal and butan-2-one share formula C₄H₈O but have different functional groups (aldehyde vs ketone) → functional group isomers. Option A = position isomers.
5-C: Cut at the O: left CH₃CH₂COO⁻ = propanoate (3C acid); right –OCH₂CH₂CH₃ = propyl (3C alcohol) → propyl propanoate.
SA1 (4 marks):
(a) 2-methylbutan-1-ol: parent chain butane (4C), methyl at C2, –OH at C1. Full structural: draw all C–C and C–H bonds explicitly with –OH on C1. Condensed: HOCH₂CH(CH₃)CH₂CH₃ [1 + 1 mark]
(b) Pentan-3-one: 5-carbon chain, C=O at C3. Full structural: CH₃–CH₂–C(=O)–CH₂–CH₃ with double bond shown. Condensed: CH₃CH₂COCH₂CH₃ [1 + 1 mark]
SA2 (4 marks):
(a) C₃H₇NO possibilities: (1) Propanamide (CH₃CH₂CONH₂) — amide; (2) 3-aminopropan-1-ol (H₂NCH₂CH₂CH₂OH) — amino alcohol. [1 mark each structural formula]
(b) Add dilute HCl at room temperature. Propanamide: amide N lone pair is delocalised into C=O → not available for protonation → no visible reaction. 3-aminopropan-1-ol: free –NH₂ (pKb ~10⁻⁴) reacts rapidly with HCl → ammonium salt forms (exothermic, pH drops). [1 mark reagent + observation; 1 mark explanation using lone pair delocalisation]
Tick when you have finished all questions.