5.4 Restriction of the use of Grignard reagents

  Alcohols, Phenols and Ethers

    1.0 Alcohols
    2.0 Classification of alcohols
    3.0 Physical properties of the alcohol
    3.0 Physical properties of the alcohols
    4.0 Preparation of Alcohol
    5.0 Grignard reagent
    6.0 Chemical properties of alcohols
    7.0 Tests for Alchols
    8.0 Ethers
    9.0 Chemical Properties of Ethers
    10.0 Aryl Ethers
    11.0 Epoxides
    12.0 Phenols
    13.0 Preparation of Phenol
    14.0 Physical Properties of Phenol
    15.0 Chemical properties of phenols

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5.4 Restriction of the use of Grignard reagents

• The Grignard reagent is a very powerful base, in effect, it contains a carbanion. Thus it is not possible to prepare a Grignard reagent from an organic group that contains an acidic hydrogen.

• Grignard reagents are powerful nucleophiles we can’t prepare a Grignard reagent from any organic halide that contains a carbonyl, epoxy, nitro or cyano group.

• This means that we prepare Grignard reagents, we are effectively limited to alkyl halide or to analogous organic halide containing carbon double bonds; internal triple bonds, ether linkage and $—NR_2$ group.

• Grignard reagents are so sensitive to acidic compounds so when we prepare a Grignard reagent we must take special care to exclude moisture from our apparatus and we must use an anhydrous ether as our solvent.