Chemistry - Halogen Derivative Question with Solution | TestHub
Number of reactions have correct major product?
Answer:
Solution:
(1) NaI / acetone (Δ) is a Finkelstein / SN2 condition (iodide displaces chloride; I⁻ is a poor base) — it does not give the elimination alkene shown. So (1) is wrong.
(2) Br₂ / H₂O → bromohydrin. The bromonium ion is opened by water at the more substituted carbon → OH ends up on the more substituted carbon and Br on the other carbon (anti addition). The drawn product matches that outcome. So (2) is correct.
(3) Br₂ / CCl₄ adds across the double bond to give a vicinal dibromide (anti addition), it does not give an allylic bromide. So (3) is wrong.
(4) NaI in DMSO (polar aprotic) causes SN2 substitution (I⁻ displaces Br⁻) and therefore inversion of configuration. The product shown keeps the same stereochemical sense (no inversion), so the drawn product is incorrect. (4) is wrong.
(5) conc. HI cleaves asymmetrical ethers: when one side is tertiary, the mechanism is SN1 (tertiary carbocation) so the tertiary side gives the tertiary iodide and the other side becomes the alcohol. The shown products match this. So (5) is correct.