See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

Step 1: Analyze Compound 1 to find X (number of enantiomers). Compound 1 is 1,4-dibromo-2,3-bis(bromomethyl)butane... more precisely it is: the molecule drawn is 2,3-dibromo-1,4-dibromobutane (i.e., 1,2,3,4-tetrabromobutane pattern) — actually the compound is: each central carbon bears CH2Br, H (dash), Br (wedge), and the C-C bond. So the compound is meso or has a specific configuration. The structure of Compound 1: C1 has groups CH2Br, H (back), Br (front/wedge), and C2. C2 has groups CH2Br, H (back), Br (front/wedge), and C1. Both stereocenters have the same arrangement of groups drawn the same way (both H on dash, both Br on wedge). Since both carbons bear identical substituents (CH2Br, H, Br, and the other chiral carbon), this is a meso compound — it has an internal plane of symmetry. A meso compound is achiral and is its own 'enantiomer' (it has no enantiomer distinct from itself). Therefore, the number of enantiomers of the given compound = 0, so X = 0. Step 2: Analyze Compound 2 to find Y (number of diastereomers). Compound 2: Left carbon (C1) has CH3 (up), H (dash/back), Br (wedge/front), and bond to C2. Right carbon (C2) has H (dash/back), H (wedge/front), CH3 (down). Wait — C2 has two H groups and one CH3 and bond to C1. If C2 has two H substituents, it is NOT a stereocenter. So C2 is -CH2- effectively... but it shows H on dash and H on wedge and CH3 going down. If C2 has: H, H, CH3, and C1 as four substituents, then two are H — C2 is not a stereocenter. Therefore Compound 2 is simply 1-bromo-1-methylpropane... actually: C1 is CHBr(CH3) connected to C2 which is CH2(CH3)... that gives 2-bromobutane. 2-bromobutane has one stereocenter and exists as R and S enantiomers. The given structure is one specific enantiomer. Its enantiomer is the other; diastereomers would be stereoisomers that are not enantiomers. With only one stereocenter, there are no diastereomers. So Y = 0. Step 3: Sum X + Y = 0 + 0 = 0. Why other options fail: - (a) 1: Would require X+Y=1, but both are 0. - (b) 3: Overcounts stereoisomers. - (c) 4: Overcounts stereoisomers. - (d) 0: Correct, as X=0 (meso compound has no enantiomer) and Y=0 (only one stereocenter means no diastereomers). Therefore, the correct answer is D.