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Model Paper 8 — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistryModel Paper 81 Mark
MCQ
The synthesis of $3-$octyne is achieved by subsequent stepwise reactions of sodium amide with an alkyne, and a bromoalkane. The bromoalkane and the other alkyne respectively are:
  • A
    $BrCH_2CH_2CH_3$ and $CH_3 CH_2 CH_2C ≡ CH$
  • B
    $BrCH_2CH_2CH_2CH_2CH_3$ and $CH_3C ≡ CH$
  • C
    $BrCH_2CH_2CH_2CH_3$ and $CH_3 CH_2C ≡ CH$
  • D
    $BrCH_2CH_2CH_2CH_2CH_3$ and $CH_3 CH_2C ≡ CH$
✓

Answer

$ 3 -$ Octyne can be synthesized as per the following stepwise conversion reactions:
Step $1.$ Formation of a Sodium alkynide, by the reaction of $1 -$butyne with sodium amide
$CH_3 CH_2 C \equiv CH+NaNH_2 \rightarrow CH_3 CH_2 C \equiv CNa^{+}+NH_3$
$1-$butyne sodium amide sodium butynide
Step $2.$ Reaction of the alkynide $($ sodium butynide$)$ with $1 -$ bromobutane
$CH_3 CH_2 C \equiv CNa^{+}+CH_3 CH_2 CH_2 CH_2 Br \rightarrow CH_3 CH_2 C \equiv CCH_2 CH_2 CH_2 CH_3+NaBr$
Sodium Butynide $1-$bromobutane $3 -$ Octyne

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