Grade 12 Physical Sciences · Matter and Materials

Draw structural formulae

Draw the structural formula, or write the condensed or molecular formula, of an organic compound from its name (propane is C₃H₈).

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Grade 12 Organic Chemistry: Representing organic compoundsMiss Martins Maths and Science

Drawing Organic Molecules Grade 12Kevinmathscience

Condensed Formula Grade 12Kevinmathscience

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Question 1.2 · May/June 2025 · Paper 2 · National (DBE) · 2 marks

1.2 Which ONE of the following is the CORRECT formula of methylbutanone?(2)

A $CH_{3} CH(OH)CH(CH_{3})CH_{3}$
B $HCOOCH(CH_{3})CH_{2} CH_{3}$
C $CH_{3} CH_{2} CH(CH_{3})CHO$
D $CH_{3} COCH(CH_{3})CH_{3}$

Work it out on paper first. Then mark yourself with the official memo, one tick at a time.

More past paper questions: draw structural formulae

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3. Question 2.3.2 · November 2023 · Paper 2 · National (DBE) · 3 marks
The letters A to H in the table below represent eight organic compounds.
2.3 Write down the:
2.3.2 STRUCTURAL formula of compound C(3)
Show the memo (3 ticks)Memo
1. ✓
  Six C atoms in longest chainA chain of six C atoms (hexane).
  1 mark · Draw structural formulae
2. ✓
  Two F atoms on third C atomTwo F atoms bonded to C3.
  1 mark · Draw structural formulae
3. ✓
  Ethyl substituent on fourth C atomAn ethyl group ( $- CH_{2} CH_{3}$ , drawn with all H atoms) on C4. See the drawing.
  1 mark · Draw structural formulae
4. Question 2.2.2 · May/June 2022 · Paper 2 · National (DBE) · 3 marks
The letters A to H in the table below represent eight organic compounds.
2.2 Write down the:
2.2.2 STRUCTURAL FORMULA of compound F(3)
Show the memo (3 ticks)Memo
1. ✓
  Five C atoms in longest chain + triple bondFive C atoms in the longest chain, with a triple bond between C2 and C3: $C - C \equiv C - C - C$ (numbered from the end nearest the triple bond).
  1 mark · Draw structural formulae
2. ✓
  Two methyl substituentsTwo $- CH_{3}$ groups on C4 (the carbon next to the triple bond on the other side).
  1 mark · Draw structural formulae
3. ✓
  Whole structure correctFull structural formula with every bond and every H atom shown: C4 has no H atoms (it has three C neighbours plus the methyls), C1 and C5 each have three H atoms.
  1 mark · Draw structural formulae
5. Question 4.1.5 · November 2025 · Paper 2 · National (DBE) · 2 marks
4.1 Study the three organic reactions I, II and III below. Compounds T and W are organic compounds. R and S are inorganic substances. Consider only the major products.

Reaction I: $HBr(g) + T \to W$
Reaction II: $W + NaOH(aq) \to CH_{3} CH(OH)CH_{2} CH_{3} + R$
Reaction III: $CH_{3} CH(OH)CH_{2} CH_{3} S T + H_{2} O (ℓ)$

Write down the:
4.1.5 STRUCTURAL formula of compound T(2)
Show the memo (2 ticks)Memo
1. ✓
  (a) Correct functional groupThe C=C double bond between carbon 2 and carbon 3 (but-2-ene, the major product).
  1 mark · Write elimination reactions and conditions
2. ✓
  (b) Whole structure correct $CH_{3} -CH=CH-CH_{3}$ drawn with all bonds and all 8 H atoms.
  1 mark · Draw structural formulae
6. Question 2.2.4 · November 2025 · Paper 2 · National (DBE) · 4 marks
The letters A to G in the table below represent organic compounds.
2.2 Write down the:
2.2.4 STRUCTURAL FORMULAE of two STRAIGHT CHAIN positional isomers of compound D(4)
Show the memo (4 ticks)Memo
1. ✓
  Isomer 1: hydroxyl group on the 1st C-atomButan-1-ol: the $- OH$ group on the first carbon of a straight chain of 4 carbons.
  1 mark · Identify and draw structural isomers
2. ✓
  Isomer 1: whole structure correct $H-O-CH_{2} -CH_{2} -CH_{2} -CH_{3}$ drawn with every bond and every H atom shown.
  1 mark · Draw structural formulae
3. ✓
  Isomer 2: hydroxyl group on the 2nd C-atomButan-2-ol: the $- OH$ group on the second carbon of a straight chain of 4 carbons.
  1 mark · Identify and draw structural isomers
4. ✓
  Isomer 2: whole structure correct $CH_{3} -CH(OH)-CH_{2} -CH_{3}$ drawn with every bond and every H atom shown.
  1 mark · Draw structural formulae

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