Choose the Best Answer · Q13
Q.Bromocyclopropane (a three-membered ring bonded directly to -Br), treated with
(i) Mg, ether then
(ii) CO2, gives A; A, treated with H3O+, gives B. 'B' is a) 2-cyclobutylacetic acid (a four-membered ring joined through an extra -CH2- to -COOH) b) cyclopropanecarboxylic acid (the three-membered ring bonded directly to -COOH) c) bicyclopropyl (two cyclopropane rings joined directly to each other) d) dicyclopropyl ketone (two cyclopropane rings joined through a -CO- group)
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Start your 14-day free trial to unlock the full solution →Step 1. Bromocyclopropane has its Br bonded DIRECTLY to a ring carbon (no -CH2- spacer between the ring and Br).
Step 2. Treated with Mg/ether (i), it forms the Grignard reagent on that SAME ring carbon: cyclopropylmagnesium bromide (A) -- the ring carbon that carried Br now carries -MgBr instead.
Step 3. A + CO2 (ii, dry ice) carboxylates that identical ring carbon (Section 12.10.4/Grignard concept: RMgX + CO2, then H3O+, gives R-COOH with the new -COOH built directly onto the Grignard's own carbon). …
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