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Alcohols Phenols and Ethers question

2016 · 9 Apr · Shift 1 · Q5
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  5. /2016 · 9 Apr · Shift 1 · Q5

Alcohols Phenols and Ethers question

2016 · 9 Apr · Shift 1 · Q5

JEE MainChemistryAlcohols Phenols and EthersMCQ+4 / −1
The gas evolved on heating CH3MgBrCH_3MgBrCH3​MgBr in methanol is :
  1. A
    HBr
  2. B
    Methane
  3. C
    Ethane
  4. D
    Propane
View written solutionFree

Correct answer: B

  1. Identify the reagent behavior

    CH3MgBrCH_3MgBrCH3​MgBr is a Grignard reagent. Grignard reagents behave like strong bases and react immediately with compounds containing an acidic hydrogen, such as alcohols.

  2. Reaction with methanol

    Methanol is CH3OHCH_3OHCH3​OH, which has an acidic hydrogen on oxygen.

    The reaction is: CH3MgBr+CH3OH→CH4+CH3OMgBrCH_3MgBr + CH_3OH \rightarrow CH_4 + CH_3OMgBrCH3​MgBr+CH3​OH→CH4​+CH3​OMgBr

  3. Gas evolved

    The alkyl part of the Grignard reagent, here CH3−CH_3-CH3​−, abstracts the proton from methanol and forms the corresponding alkane: CH3−+H+→CH4CH_3^- + H^+ \rightarrow CH_4CH3−​+H+→CH4​

    So the gas evolved is methane.

  4. Check options

    • A: HBr — not formed
    • B: Methane — correct
    • C: Ethane — not formed
    • D: Propane — not formed

Therefore, the correct answer is B: Methane.

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