NEET Chemistry Question (2026) — Solution

Step-by-step solution

Reaction of trans-but-2-ene with Br_2 in CCl_4 proceeds via anti-addition to give meso-2,3-dibromobutane. In the Newman projection given in Statement I, the front carbon has Br at 0^ , Me at 120^ , and H at 240^ . The back carbon has Br at 180^ , Me at 60^ , and H at 300^ . For this staggered conformation to be meso, it must have a center of inversion, meaning a group at angle on the front carbon must have an identical group at + 180^ on the back carbon. While the Br atoms are opposite (0^ and 180^ ), the front Me at 120^ is not opposite to the back Me at 60^ . Thus, it lacks a center of inversion and represents a chiral enantiomer. Hence, Statement I is incorrect. Reaction of cis-but-2-ene with alkaline KMnO_4 proceeds via syn-addition to give meso-butane-2,3-diol. In the Newman projection given in Statement II, the front carbon has OH at 0^ , Me at 120^ , and H at 240^ . The back carbon has OH at 60^ , Me at 180^ , and H at 300^ . Rotating the back carbon by 60^ counter-clockwise perfectly eclipses all identical groups (OH with OH at 0^ , Me with Me at 120^ , H with H at 240^ ). This indicates the presence of a plane of symmetry, confirming it is the meso isomer. Hence, Statement II is correct. Therefore, Statement I is incorrect but Statement II is correct. Answer: Statement I is incorrect but Statement II is correct