JEE Main levelSingle correct optionDifficulty 2 of 3pl259
A short fragment of a polymer chain (three repeat units, end groups shown) is drawn. How many of its C=C bonds have the two chain carbons on the same side (cis, Z)?
A2
B1
C3
D0
Answer: A
The fragment is a polyisoprene chain with mixed geometry. Assigning CIP descriptors with RDKit gives Z, E, Z. Counting the Z (cis) double bonds gives 2.