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Consider the following reaction sequence starting from cyclohexanecarboxylic acid: Cyclohexanecarboxylic acid -> (NH3, strong heating) -> A -> (Br2/KOH) -> B -> (NaNO2 + HCl) -> C -> (SOCl2, pyridine) -> D -> (NaNH2) -> E Which of the following statements is/are correct?

1. 'C' is a 2-degree alcohol.
2. 'E' cannot decolourise Br2 in water.
3. 'C' to 'D' conversion is a nucleophilic substitution reaction.
4. Formation of 'B' from 'A' is a dehydration reaction.

Correct answer: 'C' is a 2-degree alcohol.

Solution

Step 1: RCOOH + NH3, strong heating -> RCONH2 (amide) = A. Step 2: A + Br2/KOH (Hofmann bromamide) -> RNH2 = cyclohexylamine = B. Step 3: B + NaNO2/HCl -> diazonium salt, which being aliphatic decomposes with H2O to give cyclohexanol = C (secondary alcohol, since C1 of cyclohexane is bonded to two ring carbons). Step 4: C + SOCl2/pyridine -> chlorocyclohexane = D (substitution, SN2-like via chlorosulfite intermediate). Step 5: D + NaNH2 (strong base, E2 elimination) -> cyclohexene = E. Statement A: C is a 2-degree alcohol — TRUE (C1 of cyclohexanol is secondary). Statement B: E = cyclohexene has a C=C and WILL decolourise Br2/H2O — FALSE. Statement C: C->D is SOCl2 reaction on alcohol = nucleophilic substitution — TRUE. Statement D: B->A? No, B is from A by Hofmann degradation (oxidative rearrangement), NOT dehydration — FALSE.

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