See image — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

Concept: An elimination reaction involves the removal of atoms or groups from adjacent carbons to form a pi bond (double bond), resulting in an alkene or other unsaturated product. Analysis of each option: Option (a): Cyclohexanol reacts with H2SO4 (a strong acid and dehydrating agent). H2SO4 protonates the OH group, converting it into a good leaving group (water). A proton from an adjacent carbon is then removed, and water leaves, forming cyclohexene. This is a classic E1 elimination (dehydration of an alcohol). This IS an elimination reaction. Option (b): trans-1,2-dibromocyclohexane reacts with KI. Iodide (I-) acts as a nucleophile and attacks one of the bromines in an SN2-like fashion, but since the two bromines are trans (anti-periplanar arrangement), the iodide can displace one Br while the other Br leaves simultaneously as Br-, with the electrons from the C-Br bond forming a pi bond. The net result is elimination of two Br atoms (debromination) to give cyclohexene + IBr + KBr. This is an E2-type elimination (dehalogenation). This IS an elimination reaction. Option (c): Bromocyclohexane reacts with NaOCH3. Methoxide (CH3O-) is a nucleophile/base. While it can act as a base for elimination, in this case the product shown is methoxycyclohexane, where OCH3 has replaced Br. This is a substitution reaction (SN2), not an elimination reaction. Conclusion: Both (a) and (b) are elimination reactions. Option (c) is a substitution reaction. Therefore, the answer is (d) both (a) and (b). Therefore, the correct answer is D.