See image — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

Concept: This reaction is an acid-catalyzed dehydration of a secondary benzylic alcohol (1-phenyl-1-butanol... actually Ph-CH(OH)-CH2CH3, which is 1-phenylbutan-2-ol... reading structure: Ph-CH(OH)-CH2-CH3 = 1-phenyl-1-propanol with ethyl... let me re-read: the structure is Ph-CH(OH)-CH2-CH3, i.e., Ph attached to CH(OH), then CH2, then CH3. This is 1-phenylbutan-2-ol). Under H+ (acid), this secondary benzylic alcohol undergoes E1 elimination to give Ph-CH=CH-CH3 (1-phenyl-1-propene, both E and Z isomers). Step 1 - Identify the reaction type: Loss of water (OH and H) from the alcohol under acidic conditions = dehydration reaction. Statement (a) is TRUE. Step 2 - Identify the mechanism: The alcohol is secondary and benzylic, so under acidic conditions it forms a stable carbocation (secondary benzylic carbocation) and then loses a proton. This is E1 mechanism. Statement (b) is TRUE. Step 3 - Stereoselectivity: E1 reactions do not require a specific anti-periplanar arrangement (unlike E2). In E1, the carbocation intermediate can lose a proton from either face, giving both E and Z products. However, the reaction does show some stereoselectivity because the E (trans) isomer is more stable (less steric strain between the phenyl group and the methyl group). The E-isomer is typically the major product due to thermodynamic stability. Statement (c) says the reaction is stereoselective - this is TRUE because a preference for one stereoisomer (E) over the other exists. Step 4 - Evaluate statement (d): Statement (d) claims the major product is the Z-alkene. In the E1 elimination giving Ph-CH=CH-CH3, the E-isomer (trans, where Ph and CH3 are on opposite sides) is more stable due to reduced steric interaction. Therefore, the E-isomer is the major product, NOT the Z-isomer. The Z-isomer would place the larger groups (Ph and CH3) on the same side, causing steric strain. Thus statement (d) is NOT TRUE. Why other options fail: (a), (b), and (c) are all correct statements about the reaction, leaving (d) as the false statement. Therefore, the correct answer is D.