Treatment of buta-1,3-diyne with (2 equivalents), followed by reaction with excess of trans- gives X as the major product. The maximum number of carbon atoms that are collinear (in a straight line) in X is ____.
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JEE Advanced 2026 · Paper 1, Chemistry question 12
Answer and worked solution
Official answer: 6
Product. Two equivalents of remove both terminal protons of . The dianion is then alkylated twice by crotyl bromide:
Collinear carbons. The four sp carbons lie on a line. Each sp carbon has bond angle 180°, so the two carbons bonded to the ends also lie on that line. The next carbons () are attached at the tetrahedral and leave the line.
Maximum .