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To convert benzene into a compound having both a vinyl group (-CH=CH2) and a methyl group on the ring (i.e., 4-methyl styrene / vinyl toluene), choose the correct sequence of reagents from the list below: (i) CH3COCl / AlCl3 (anhydrous) (ii) CH3Cl / AlCl3 (anhydrous) (iii) CH3CHCl2 / AlCl3 (anhydrous) (iv) Al2O3 / heat

1. CH3COCl / AlCl3 (Anh.)
2. CH3Cl / AlCl3 (Anh)
3. CH3CHCl2 / AlCl3 (Anh)
4. Al2O3 / Δ

Correct answer: CH3COCl / AlCl3 (Anh.)

Solution

Friedel-Crafts acylation of benzene with CH3COCl/AlCl3 gives acetophenone (C6H5-CO-CH3). Dehydration of acetophenone over Al2O3 at high temperature gives styrene (C6H5-CH=CH2). To get vinyl toluene, toluene is used as starting material, but this problem states benzene as start. The most plausible two-step sequence is CH3COCl/AlCl3 followed by Al2O3/heat.

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