Chemistry, WM Revision Notes




Physical Properties of Alcohols

  • Polar due to \(O\)-\(H\) bond

  • Able to hydrogen bond

    • Explains why alcohols have higher MBP’s than corresponding alkanes

    • Also explains why alcohol and water mix

  • \(O\)-\(H\) bond becomes less influential in longer chains

    • Solubility in water decreases

    • Other properties more similar to those of corresponding alkanes

Reactions of Alcohols

Types of alcohols

Primary alcohols:

  • -\(O\)-\(H\) carbon bonded to one other

Secondary alcohols:

  • -\(O\)-\(H\) carbon bonded to two others

Tertiary alcohols:

  • -\(O\)-\(H\) carbon bonded to three others


  • The \(O\)-\(H\) group is oxidised by strong oxidising agents

    • Acidified Potassium Dichromate(VI), \(K_2Cr_2O_7\)

      • Orange dichromate ion reduced to green chromate(III) ion

      • \(Cr_2O_7^{2-}\Rightarrow Cr^{3+}\)

  • \(O\)-\(H\) group converted to carbonyl \(C\)=\(O\) group

  • Will not take place if there is no hydrogen attached to the carbon

  • Carbonyl formed depends on reacting alcohol and conditions

    • Aldehyde or ketone

Heating under Reflux

  • Safer when using volatile compounds

  • Prevents loss of solvent, reagent, or product

Oxidation of Primary alcohols

  • Initially oxidised to an Aldehyde

  • Can be further oxidised to a Carboxylic Acid

    • Excess oxidising agent

    • Under reflux

  • If the Aldehyde is required:

    • Distilled in situ

      • Prevents further oxidation

    • Excess Alcohol

    • No reflux

Oxidation of Primary Alcohols

Oxidation of Secondary alcohols

  • Oxidised to ketones

    • Excess oxidising agent

    • Under reflux

  • No further oxidation

    • Due to strong \(C\)-\(C\) bond