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Chloroalkyl ether

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Chloroalkyl ether

Chloroalkyl ethers are a class of organic compounds with the general structure R-O-(CH2)n-Cl, characterized as an ether connected to a chloromethyl group via an alkane chain.

Contents

Chloromethyl methyl ether (CMME) is an ether with the formula CH3OCH2Cl. It is used as an alkylating agent and industrial solvent to manufacture dodecylbenzyl chloride, water repellents, ion-exchange resins, polymers, and as a chloromethylation reagent. It is a known human carcinogen. In organic synthesis the compound is used for the introduction of the methoxymethyl (MOM) protecting group.

Closely related compounds of industrial importance are bis(chloromethyl) ether (BCME) (closely related to chemical weapon sulfur mustard) and benzyl chloromethyl ether (BOMCl).

Alcohol protection

2-Methoxyethoxymethyl (MEM) group is commonly used in organic synthesis as a protecting group for alcohols.

Most common protection methods

  • Treatment of alcohol with bases such as sodium hydride or potassium hydride and 2-methoxyethoxymethyl chloride in tetrahydrofuran (THF) at 0 °C
  • MEM group can also be installed at ambient temperature with 2-methoxyethoxymethyl chloride and a mild base such as N,N-diisopropylethylamine (DIPEA) in dichloromethane

    • Most common deprotection methods

    The 2-methoxyethoxymethyl protecting group can be cleaved with a range of Lewis acids, including but not limited to:

  • TiCl4 or ZnBr2 in dichloromethane at 0 °C to ambient temperature
  • If the solvent of choice is a protic solvent such as methanol, formic acid can be used to cleave MEM group at elevated temperatures

    • _____________________________

    Methoxymethyl (MOM) is used as a protecting group for alcohols in organic synthesis.

    Most common protection methods

  • Treatment of alcohol with N,N-diisopropylethylamine (DIPEA) and methoxymethyl chloride (MOM chloride) in dichloromethane at 0 °C
  • For reactions carried out in more polar solvents such as tetrahydrofuran (THF) or N,N-dimethylformamide (DMF), protection of alcohol can be carried out using sodium hydride at 0 °C to ambient temperatures

    • Most common deprotection methods

    MOM group can be cleaved with acid, commonly used conditions for deprotection of MOM alcohols include:

  • Concentrated hydrochloric acid in methanol or water
  • Trifluoroacetic acid (TFA) in dichloromethane
  • Acetyl chloride in methanol at 0 °C

    • References

    Chloroalkyl ether Wikipedia
    (Text) CC BY-SA