$\mathrm{CH_3{-}CH_2{-}\underset{\textstyle |\;\,}{\underset{\textstyle OH}{CH}}{-}CH_3} \;\xrightarrow[\text{(iii) } \mathrm{D_2O}]{\;\text{(i) NaI, } \mathrm{H_3PO_4}\;;\;\text{(ii) Mg, dry ether}\;}\; [X]$ Product $[X]$ formed in the above reaction is:

(A) $\mathrm{CH_3{-}CH_2{-}\underset{\textstyle |\;}{\underset{\textstyle D}{CH}}{-}CH_3}$ (butane-2-$d$)

(B) $\mathrm{CH_3{-}CH_2{-}\underset{\textstyle |\;\,}{\underset{\textstyle OH}{CH}}{-}CH_3}$ (butan-2-ol, unchanged alcohol)

(C) $\mathrm{CH_3{-}CH_2{-}CH{=}CH_2}$ (but-1-ene)

(D) $\mathrm{CH_3{-}CH{=}CH{-}CH_3}$ (but-2-ene)

JEE Main · 2023 · 11 Apr 2023 · Shift 2 · Haloalkanes and Haloarenes

C H_{3} - C H_{2} - ∣ O H CH - C H_{3} (i) NaI, H_{3} P O_{4}; (ii) Mg, dry ether (iii) D_{2} O [X]

Product

[X]

formed in the above reaction is:

Answer: (A)

(i)

NaI/ H_{3} P O_{4}

converts butan-2-ol into 2-iodobutane,

C H_{3} C H_{2} CHIC H_{3}

. (ii) Mg in dry ether gives the Grignard reagent

C H_{3} C H_{2} CH (MgI) C H_{3}

. (iii)

D_{2} O

(a source of

D^{+}

) deuterates the carbanionic carbon, replacing MgI by D. The product

[X]

C H_{3} C H_{2} CHDC H_{3}

, i.e. butane-2-

d

— option (A).

JEE Main · 2023 · 11 Apr 2023 · Shift 2 · Single correct option