The presence of 11-cis retinal, C20H28O, in cells in the eye is important for vision. The structure of retinal includes an aldehyde group, a cyclohexene ring and a long aliphatic side chain, in which a carbon-carbon double bond exists between carbons numbered 11 and 12. Which pair of statements about 11-cis retinal could be correct?
✓ Correct Answer
The correct answer is A: total number of >C=C< double bonds: 5, arrangement around the adjacent carbons 11 and 12: [Diagram showing R1 and R2 on the same side (cis) of the double bond]
📋 Examiner Report & Trap Analysis
Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
🎯 Mark Scheme Breakdown
Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.
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