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5.5: Common Acids and Bases

  • Page ID
    28113
  • Acidity of Carboxylic AcidsEdit section

    The pKa 's of some typical carboxylic acids are listed in the following table. When we compare these values with those of comparable alcohols, such as ethanol (pKa = 16) and 2-methyl-2-propanol (pKa = 19), it is clear that carboxylic acids are stronger acids by over ten powers of ten! Furthermore, electronegative substituents near the carboxyl group act to increase the acidity.

    Compound

    pKa

    Compound

    pKa

    HCO2H 3.75 CH3CH2CH2CO2H 4.82
    CH3CO2H 4.74 ClCH2CH2CH2CO2H 4.53
    FCH2CO2H 2.65 CH3CHClCH2CO2H 4.05
    ClCH2CO2H 2.85 CH3CH2CHClCO2H 2.89
    BrCH2CO2H 2.90 C6H5CO2H 4.20
    ICH2CO2H 3.10 p-O2NC6H4CO2H 3.45
    Cl3CCO2H 0.77 p-CH3OC6H4CO2H 4.45

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