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Alcohols - Revision Notes

1. General

  • Functional group is -OH
  • General formula is CnH2n+1OH
  • The –OH group means that alcohols hydrogen bond with each other. Alcohols have low volatility (high boiling points) for their size because the hydrogen bonds have to be broken
  • Alcohols are highly soluble in water because hydrogen bonding occurs between –OH of alcohols and water molecules

2. Classifying Alcohols

  • Classified according to the number of carbons attached to C-OH
  • Primary alcohols have 1 carbon attached e.g. ethanol
  • Secondary alcohols have 2 carbons attached e.g. propan-2-ol
  • Tertiary alcohols have 3 carbons attached e.g. 2-methylpropan-2-ol

Primary 1° Secondary 2° Tertiary 3°

3. Reactions of Alcohols

  • Reagents = the other chemicals needed
  • Conditions = required temperature, pressure, catalyst etc

a) Combustion

  • Example C2H5OH + 3O2 ® 2CO2 + 3H2O
  • Balance C’s then H’s then O’s
  • Don’t forget the O in the OH when balancing

b) Dehydration to form an alkene

  • Example C2H5OH ® CH2=CH2 + H2O
  • Needs heat and a strong acid catalyst (concentrated sulphuric acid or concentrated phosphoric acid)

c) Reaction with a carboxylic acid to form an ester (esterification)

  • Carboxylic acids contain the functional group –COOH, esters have the form RCOOR’
  • Example C2H5OH + CH3COOH ® CH3COOC2H5 + H2O

Ethanoic acid ethyl ethanoate

  • Conditions catalyst of concentrated H2SO4

d) Oxidation of primary alcohol to aldehyde


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