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JAMB Chemistry 1990 Question 43

Question 43

Introduction to Organic Chemistry

What is the IUPAC name for the hydrocarbon CH3—C(CH2CH3) = CH—CH(CH3)—CH3? (structure in the figure)

Diagram for this question
  1. A.2-ethyl-4-methylpent-2-ene
  2. B.3,5-dimethylhex-3-ene
  3. C.2, 4-dimethylhex-3-ene
  4. D.2-methyl-4-ethylpent-3-ene.
Show the answer and explanation

Answer: C (2, 4-dimethylhex-3-ene)

Explanation

The longest chain with the double bond has six carbons (it runs through the ethyl group). Numbered to give the lowest locants, the double bond is at C3 and the methyl groups at C2 and C4: 2,4-dimethylhex-3-ene.