Convert the following :(i) acetaldehyde to isopropyl alcohol.(ii) cumene to phenol.(iii) anisole to phenol.Write two uses of neon.

Answer:

(i) Acetaldehyde to isopropyl alcohol: add methylmagnesium bromide, then hydrolyse.

CH₃CHO + CH₃MgBr → (dry ether) (CH₃)₂CH–OMgBr → (H₃O⁺) (CH₃)₂CH–OH + Mg(OH)Br

(ii) Cumene to phenol: cumene (isopropylbenzene) is oxidised by air to cumene hydroperoxide, which is cleaved by dilute acid.

C₆H₅–CH(CH₃)₂ + O₂ → (air, Δ) C₆H₅–C(CH₃)₂–O–O–H (cumene hydroperoxide)

C₆H₅–C(CH₃)₂–OOH → (dil. H₂SO₄) C₆H₅OH + CH₃COCH₃

(iii) Anisole to phenol: heating with concentrated HI cleaves the ether.

C₆H₅–O–CH₃ + HI → (Δ) C₆H₅OH + CH₃I

Uses of neon:

1. Neon is used in discharge tubes and fluorescent bulbs for advertisement (neon) signs, which glow orange-red.
2. It is used in beacon lights for aircraft and in safety devices, voltage stabilisers and (mixed with helium) in He–Ne lasers.