Two statements — Statement-I: trans-But-2-ene on treatment with Br₂ in CCl₄ gives the shown product (a meso-2,3-dibromobutane). Statement-II: cis-But-2-ene on treatment with alkaline KMnO₄ gives the shown product (meso-butane-2,3-diol). Choose the most appropriate answer:

Solution & Explanation

Concept: anti (trans) addition of Br₂ vs syn addition of cold alkaline KMnO₄ decides the stereochemistry of the product from a given geometric alkene. Statement-I: Br₂ in CCl₄ adds anti (the bromonium ion opens by backside attack). Anti addition of Br₂ to trans-but-2-ene gives the (±) d,l (racemic) pair of 2,3-dibromobutane, NOT the meso form. So the shown meso product is wrong → Statement-I is incorrect. Statement-II: alkaline KMnO₄ does syn (cis) dihydroxylation, adding both –OH groups to the same face. Syn addition to cis-but-2-ene gives meso-butane-2,3-diol, which matches the shown product → Statement-II is correct. Key rule of thumb: anti addition to a trans alkene → meso would arise from a cis alkene, and vice versa; the cancellation of one inversion against the cis/trans geometry is the deciding step. Hence the answer is D — Statement-I is incorrect but Statement-II is correct.