Carboxylic Acids and Derivatives

• What is a carboxylic acid

  -COOH (C=O AND C-OH)
• How do you name carboxylic acids

  -oic acid
• Are carboxylic acids soluble in water

  • YES
  • Acid group can form hydrogen bonds with water molecules
• What are the intermolecular forces in carboxylic acids

  Hydrogen bonds in solid state -> very strong
• What are esters

  • Formed from CARBOXYLIC ACIDS and ALCOHOLS
  • RCOOR (C=O,C-O-C)
• Write an equation for the reaction of ethanoic acid with propan-1-ol

  CH3COOH + CH3CH2CH2OH -> CH3COOCH2CH2CH3 + H2O
• How do you name esters

  • Start with the group that has replaced the HYDROGEN
  • Then the acid part
  • E.G -> Propyl (from the alcohol) ethanoate (from the carboxylic acid)
• What characteristic physical properties do esters have

  • Volatile
  • Pleasant fruity smells
• What are some uses of esters

  • Flavourings
  • Perfumes
  • Solvents (shorter chains)
  • Plasticisers
• What are some common natural esters

  Fats and oils
• How is the carboxylic acid group polarised

  The O's are delta NEGATIVE

  The C is delta POSITIVE

  The H is delta POSITIVE

  
• Write an equation for the equilibrium formed by ethanoic acid in solution

  CH3COOH (aq) <-> CHCOO- (aq) + H+ (aq)
• What happens to the negative charge on the ethanoate ions in terms of electrons

  • Electrons delocalise
  • The negative charge is shared across the WHOLE of the carboxylate group
• How could you distinguish carboxylic acids from other -OH containing compounds

  • Add NaHCO3
  • Acids will produce sodium salt, water and carbon dioxide
• Write an equation for the reaction of ethanoic acid with NaOH

  CH3COOH + NaOH -> H2O + CH3COO-Na+
• Write an equation for the reaction of ethanoic acid with Na2CO3

  2CH3COOH + Na2CO3 -> 2CH3COO-Na+ + H2O + CO2
• What catalyst is needed for the formation of esters from alcohols and carboxylic acids

  CONCENTRATED strong acid such as H2SO4
• What catalyst is needed for the hydrolysis of esters

  DILUTE strong acid H2SO4
• What is an alternative method of hydrolysis

  Base hydrolysis
• What are the advantages of base hydrolysis

  • Reaction goes to completion due to neutralisation by base
  • More product in the mixture than acid catalysed hydrolysis
• Which alcohol forms the ester that makes up animal and vegetable oils

  • Glycerol/ propane -1,2,3 -triol
• What is the difference between oil and fat

  • Oils are liquid at room temperature
  • Fats are solid
  • Fats are usually saturated, oils are NOT
• What are the products of hydrolysing fats and oils

  • Propane-1,2,3-triol and sodium salts of the acids
  • It makes up the ester
  • Hydrolysed with NaOH
• What are the uses of Propane-1,2,3-triol and sodium salts

  Soaps and cleaning products
• What does the long hydrocarbon chain of the carboxylate ion do

  Mixes with grease
• What does the COO- group do

  MIxes with water
• How does the carboxylate ion with a long carbon chain make a good cleaning agent

  Means that grease can be removed with water
• What is the systematic name of glycerol

  propane-1,2,3-triol
• What are some of the common uses of glycerol

  • Used in pharmaceutical and cosmetic preparations
  • Solvent in many medicines
  • Solvent in the food industry
• How do you make biodiesel

  • NaOH catalyst
  • 60 degree
  • Lipids (fats/oils -esters) + 3CH3OH -> 3 methyl esters + glycerol
• What does transesterification mean

  Converting one type of ester to another
• What kind of crops is biodiesel made from

  Rapeseed oil or soybean oil
• How is the reaction mixture of biodiesel purified and separated

  • Settling tank or centrifuge
  • Remove remainder with water
  • Add acid to neutralise excess alkali catalyst
  • Solid soap is formed so it is easy to remove
• What is a problem with producing biodiesel

  Crops that could be used to make food are being used to make fuel -> are the resources being best used
• What are carboxylic acid derivatives

  Molecules that have the acyl group as a part of their structure, formed from carboxylic acids
• Name two acid derivatives and give their functional groups

  • Acyl chlorides: RCOCL
  • Acid Anhydrides: RCOOCR/(RCO)2O
• Draw the mechanism for the acylation of a nucleophile by an acid derivative

  .

  
• Which factor determines how readily the acylation of a nucleophile by an acid derivative occurs

  • Magnitude of the delta POSITIVE CHARGE on the CARBONYL carbon, which depends on the electronegativity of the atom being substituted
  • How easily the atom/group being substituted is lost
  • How good the nucleophile is (how easily it will donate electrons)
• What effect do the Cl and O atoms in the acyl chlorides/ acid anhydrides have on the partial charge of the carbonyl group

  • INCREASE the partial positive charge by ATTRACTING electrons
  • This means that they react more readily with nucleophiles
• Are acyl chlorides or acid anhydrides more reactive

  Acyl chlorides