Q20 · CSIR NET Chemistry, December 2015
Paper: CSIR NET December 2015 · Subject: Organic Chemistry · Chapter: Reagents, Reaction Mechanisms & Named Reactions · Topic: Reagents, Reaction Mechanisms & Named Reactions – General · Marks: 2 · Difficulty: Hard
The major structures of A and B in the following reaction sequence are 
$\mathrm{PhCOOH,\ DCC}$ 
A $\xrightarrow[\text{then alumina}]{\mathrm{PDC,\ CH_2Cl_2}}$ B
$\mathrm{PhCOOH,\ DCC}$ A $\xrightarrow[\text{then alumina}]{\mathrm{PDC,\ CH_2Cl_2}}$ B(a)A = 
B = 
B = (b)A = 
B = 
B = (c)A = 
B = 
B = (d)A = 
B = 
B = Answer
Answer: A ✓ checked by 4AB · confidence high
Explanation
DCC/DMAP benzoylates the less hindered primary alcohol (A); PDC oxidises the secondary alcohol to the ketone and alumina promotes β-elimination of benzoate, giving the α-methylene ketone (a).
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