carboxylic acids and derivatives

• What is the solubility of smaller carboxylic acids (up to C4) in water?


  They dissolve in water in all proportions.
• Why do smaller carboxylic acids dissolve in water?


  Because they can hydrogen bond to the water molecules.
• How does the solubility of carboxylic acids change after C4?


  It rapidly reduces.
• What type of acids are carboxylic acids in water?


  They are only weak acids.
• What happens when carboxylic acids dissociate in water?


  They only slightly dissociate.
• What can carboxylic acids displace from carbonates?


  Carbon dioxide.
• How are carboxylic acid salts stabilized?


  By delocalisation.
• What effect does delocalisation have on the C-O bond lengths in carboxylic acid salts?


  It makes them equal.
• What does delocalisation do to the stability of the ion?


  It makes the ion more stable.
• How does increasing chain length affect the strength of carboxylic acids?


  It makes the acid less strong.
• What is the effect of alkyl groups on carboxylic acids?


  They are electron releasing.
• How do electronegative chlorine atoms affect carboxylic acids?


  They withdraw electron density, making the acid stronger.
• Which is less acidic: propanoic acid or ethanoic acid?


  Propanoic acid.
• Which is more acidic: chloroethanoic acid or ethanoic acid?


  Chloroethanoic acid.
• What is the naming convention for carboxylic acids?


  • Ending in -oic acid
  • No number is necessary for the acid group
  • Numbering starts from the carboxylic acid end
• What is the name for a carboxylic acid with groups on both ends of the chain?


  It is called a -dioic acid.
• What do carboxylic acids react with to form esters?


  Alcohols, in the presence of a strong acid catalyst.
• What are the components of an ester name?


  • The part ending in -yl comes from the alcohol
  • The part ending in -anoate comes from the carboxylic acid
• What is the general reaction for ester formation?


  Carboxylic acid + alcohol → ester + water.
• What conditions are needed for ester formation?


  Heating under reflux with an acid catalyst.
• What is the typical yield of ester formation?


  About 50%.
• What is the effect of heating under reflux on the ester formation reaction?


  It allows the reaction to proceed more effectively.
• What are the properties required for esters used in perfumes?


  They need to be non-toxic, soluble in ethanol, volatile, and not reactive with water.
• Why do esters have lower boiling points than carboxylic acids?


  Because they do not form hydrogen bonds.
• How are esters used as solvents?


  They can dissolve polar organic substances.
• What is the role of plasticisers in polymers?


  They allow polymer chains to move more easily, increasing flexibility.
• What is unique about methanoic acid regarding oxidation?


  It can be oxidised because it has an aldehyde group.
• What does methanoic acid form when oxidised?


  Carbonic acid (H2CO3), which can decompose to give CO2.
• What types of reactions can carboxylic acids undergo to form salts?


  • Acid + metal → salt + hydrogen
  • Acid + alkali → salt + water
  • Acid + carbonate → salt + water + CO2
• What is the functional group test for carboxylic acids?


  The effervescence caused by CO2 production with Na2CO3 or NaHCO3.
• How can esters be hydrolysed?


  By heating with acid or sodium hydroxide.
• What is produced when an ester is hydrolysed with acid?


  A carboxylic acid and an alcohol.
• What is produced when an ester is hydrolysed with sodium hydroxide?


  A carboxylic acid salt and an alcohol.
• Why is the hydrolysis of esters with sodium hydroxide not reversible?


  Because the carboxylic acid salt product is resistant to attack by weak nucleophiles.
• What happens when excess sodium hydroxide is used in ester hydrolysis?


  It ensures the ester is completely hydrolysed.
• What is the practical method for the formation and hydrolysis of esters?

  • Heating under reflux
  • Use of acid catalyst for formation
  • Purification steps for esters
• What happens when a strong acid is added to a carboxylic acid salt?


  It converts the salt to the carboxylic acid form.
• What is the result of hydrolysing ethyl benzoate with sodium hydroxide?


  Sodium benzoate and an alcohol are produced.
• What happens after hydrolysing ethyl benzoate and cooling the mixture?


  Hydrochloric acid is added to produce a precipitate of benzoic acid.
• Why is sodium benzoate soluble in water while benzoic acid is not?


  Sodium benzoate is ionic, while benzoic acid has a non-polar benzene ring.