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Consider the following reaction sequence starting from cyclohexanecarboxamide: cyclohexanecarboxamide --(Br2/KOH)--> A --(HNO2/H2O)--> B --(conc. H2SO4, heat)--> C --(KMnO4/H+)--> D --(LiAlH4)--> E --(SOCl2, 1 eq)--> F --(NaH)--> G --(cyclisation)--> H. Find y = number of hydrogen atoms in compound H.

1. 6
2. 8
3. 10
4. 12

Correct answer: 8

Solution

Step by step: Cyclohexanecarboxamide (C6H11-CONH2) + Br2/KOH (Hofmann rearrangement) -> A = cyclohexylamine (C6H11-NH2). A + HNO2/H2O (diazotization then hydrolysis) -> B = cyclohexanol (C6H11-OH). B + conc. H2SO4, heat (dehydration) -> C = cyclohexene (C6H10). C + KMnO4/H+ (oxidative cleavage of double bond) -> D = hexanedioic acid (adipic acid, HOOC-(CH2)4-COOH). D + LiAlH4 (reduction of carboxylic acids) -> E = hexane-1,6-diol (HO-CH2-(CH2)4-CH2-OH). E + SOCl2 (1 eq) -> F = 6-chlorohexan-1-ol (Cl-CH2-(CH2)4-CH2-OH). F + NaH -> G = deprotonated alcohol (alkoxide: Cl-CH2-(CH2)4-CH2-O-Na+). G + cyclisation (intramolecular Williamson ether synthesis) -> H = oxepane (7-membered cyclic ether, oxacycloheptane). Oxepane: C6H12O. Number of H atoms = 12.

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