Topic 9 Carboxylic acids and esters

• Carboxylic acids contain the carboxylic functional group COOH
• Carboxylic acids are weak acids
• In water carboxylic acids partially dissociate
• How does a carboxylic acid form an ester? [3]

  Reacts with an alcohol

  heating carboxylic acid with an alcohol in the presence of a strong acid catalyst, which is usually sulphuric acid
• What is the reaction called when an ester is formed? [1]

  Esterification
• Esters have the functional group COO-
• The name of an ester is made up of two parts: first the alcohol group, second the carboxylic acid
• Name this ester CH3COOCH2CH2CH3[1]

  propyl ethanoate
• What are the use of esters? [3]

  Sweet smell so used in perfumes and to flavour things in food

  Esters are polar liquids with a low boiling point so used to dissolve stuff so good solvents in glues and printing inks

  Used as plasticers- added to plastic to make it more flexible
• Name the two types of hydrolysis of esters? [2]

  Acid hydrolysis

  base hydrolysis
• What is acid hydrolysis? [3]

  Splits the ester into an acid and an alcohol. You have to reflux the ester with a dilute acid such as HCL or sulfuric acid H2SO4
• An ester can be used to make soap by hydrolysing vegetable oil and animal fats. Animal fats are saturated and solid at room temp so high van der waals. Vegetable oils are liquid at room temp and unsaturated so bent so less van der waals
• What is biodiesel ? [3]

  Vegetable oils make good fuels but can’t be directly used in car engines

  Oils must be converted to biodiesel which involves reacting them with methanol using KOH as a catalyst

  You get a mixture of methyl esters of fatty acids aka biodiesel
• What are the 4 molecules in which acrylic chlorides react with? [4]

  Water, alcohols, ammonia, primary amines
• Acyl chlorides produce a vigorous reaction with cold water, producing a carboxylic acid

  CH3COCl + H2O -> CH3COOH + HCl
• Acyl chlorides produce a vigorous reaction at room temperature with alcohols, producing an ester

  CH3COCl + CH3OH -> CH3COOCH3 + HCl
• Acyl chlorides produce a violent reaction at room temperature with ammonia, producing an amide

  CH3COCL + NH3 -> CH3CONH2 + HCl
• Acyl chlorides produce a violent reaction at room temperature with primary amines, producing an N-substituted amide

  CH3COCl + CH3NH2 -> CH3CONHCH3 + HCl
• What is an acid anhydride made from? [1]

  Made from two identical carboxylic cid molecules
• An acid anhydride reacting with water,alcohol,ammonia and a primary amines is less vigorous than Acyl chlorides and a carboxylic cid is produced instead of HCl
• See notes for nucleophillic addition- eliminationn
• Aspirin is an ester- made by reacting salicylic acid with ethanoic anhydride or ethanoyl chloride.
• Why is ethanol anhhydride used more than ethanoyl chloride? [2]

  Cheaper

  Safer