See image — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Step 1: Identify the starting material. The structure drawn shows a conjugated diene, specifically hexa-2,4-diene (CH3-CH=CH-CH=CH-CH3), which has two internal double bonds in conjugation. Step 2: Reaction with 2 equivalents of Br2 in CCl4 is an electrophilic addition (anti addition) across both double bonds. Each Br2 adds in an anti (trans) fashion across each double bond. Step 3: Identify the stereocenters formed. Addition of Br2 across both double bonds of hexa-2,4-diene generates four stereocenters: C2, C3, C4, and C5, each bearing a Br and H (or methyl at the ends). Actually, the product is 2,3,4,5-tetrabromohexane with stereocenters at C2, C3, C4, and C5. Step 4: Analyze the stereochemical outcomes. Because of anti addition to each double bond and the symmetry of the molecule (it is a symmetric molecule — CH3 groups at both ends), we consider: - Anti addition to the C2=C3 double bond gives one relative configuration at C2 and C3. - Anti addition to the C4=C5 double bond gives one relative configuration at C4 and C5. - The molecule has a plane of symmetry (C2 symmetry), so some combinations of products are identical or meso. Step 5: Enumerate the stereoisomers. For 2,3,4,5-tetrabromohexane (a symmetric molecule), the possible stereoisomers from anti addition are: 1. (2R,3S,4R,5S) — anti addition to both double bonds, this is a meso compound due to internal symmetry. 2. (2R,3S,4S,5R) — another combination; given the molecular symmetry this may also be meso or identical to above. 3. (2R,3R,4S,5S) or (2S,3S,4R,4R) — a pair of enantiomers (one dl pair). This gives 3 stereoisomeric tetrabromides: two meso compounds (or one meso and one dl pair counting as 2 stereoisomers plus one more), totaling 3 distinct stereoisomers. Step 6: Why not other answers? Option (a) 2 undercounts — it misses one stereoisomeric form. Option (c) 4 and (d) 6 overcount because molecular symmetry reduces the number of distinct stereoisomers (some would be identical due to the symmetric nature of the molecule). Therefore, the correct answer is B.