3.9 Carboxylic Acids and Derivatives

• What is the functional group of a Carboxylic acid?

  R-COOH
• Why are Carboxylic acids weak acids? Give an equation.

  They do not fully dissociate in water

  CH3COOH(aq) -> CH3COO- + H+
• Why can the proton be released?

  The polarised C=O group attracts electrons away from the O-H group. This weakens the O-H bond enabling the proton to be released. This does not happen in alcohols as there is no C=O to weaken this bond
• How are Carboxylic acids produced?

  Produced by the oxidation of primary alcohols or aldehydes
• How do (hydrogen)carbonates react with Carboxylic acids?

  To produce salt water and carbon dioxide

  
  

  R-COOH(aq) + Na2CO3(aq) -> R-COO-Na+(aq) + CO2(g) + H2O(l)
• How can you test for the presence of CO2?

  Passing the gas produced through lime water which can confirm the reactant is a Carboxylic acid.
• How do Carboxylic acids react with alcohols?

  In the presence of concentrated H2SO4 to form ester and water in a reaction called esterification

  R-C-O-H + R-COOH _> R-(O-C=O)-R

  *conc H2SO4 acts as a catalyst and the reaction is carried out under warm reflux
• How do you name salts of carboxylic acids?

  Prefix is the name of the metal and the suffix is -oate e.g. CH3COONA = sodium ethanoate
• How do you name an ester?

  First component of an ester name is derived from the alcohol but using the suffix -yo. The second component is from the Carboxylic acid with the suffix -oate
• What does hydrolysis of esters produced and how is this possible?

  Produces carboxylic acid and alcohol. It is possible because the carbonyl in the ester is susceptible to nucleophilic attack
• What occurs in acid-catalysed hydrolysis?

  Refluxing an ester with an acid, usually conc H2SO4/HCl produces a Carboxylic acid and alcohol

  R1-COO-R2 + H2O -> R1-COOH + R2-OH
• What occurs in base-catalysed hydrolysis?

  Produces a carboxylate salt of the carboxylic acid and involves boiling the ester with aqueous NaOH

  R1-COOR2 + NaOH -> R-COO-Na+ + R2-OH
• What is NaOH in this reaction?

  Not a catalyst but a reactant. The equilibrium can be moved to right by using excess NaOH. It is more efficient method than acid hydrolysis
• What is saponification?


  Alkaline hydrolysis of animal fats and vegetable oil into glycerol and sodium salt of the long chain fatty acid formed
• What are esters used as?


  -short chain esters are used in artificial flavourings and perfumes

  -sweet smell can also be used to test for the presence of carboxylic acids and alcohols

  -plasticise as they can be added to polymers to make them less rigid and more flexible

  -used as solvents for organic compounds as short chain esters are volatile

  -biodiesel which is a mixture of methyl esters and long chain Carboxylic acids
• What is the functional group and name of an acyl halides in the presence of chloride?

  R-C=O)-Cl

  Suffix -oylchloride
• What is the functional group and name of an acid anhydride with the same R group?

  R1-C=OOC=O- R1

  Suffix - oic anhydride
• What is the functional group and name of an acid anhydride with different R groups?

  R1-C=OOC=O - R2

  Suffix R1-oic, R2-oic anhydride

  *name alphabetically
• What is the functional group and name of a primary amide?

  R1-C=ONH2

  Suffix -amide
• What is the functional group and name of a secondary amide?

  R1-C=ONHR2

  Suffix -amide

  Prefix N-
• What is the functional group and name of a tertiary amide?

  R1-C=O-NR2R3

  Suffix -amide

  Prefix N,N-
• What are the four stages of an addition-elimination reaction of acyl chlorides?

  1) Attraction - carbonyl carbon attracts the lone pair of electrons on the nucleophile

  2) Addition - nucleophile addition occurs and the carbonyl double bond is broken

  3) Elimination - the addition product eliminates the chlorine as an ion and the carbonyl double bond is reformed

  4) Deprotonation - the new compound is formed by the removal of a proton
• How do acyl chlorides react with water?

  RCOCl + H2O -> RCOOH + HCl

  If the acyl chloride is hydrolysed in alkaline solution, the carboxylate ion is formed instead of acid
• How do acyl chlorides react with alcohol?

  RCOCl + R2-OH -> R1-COO-R2 + HCl

  This method avoids the equilibrium problem associated with acid catalysed esterification
• How do acyl chlorides react with primary amines?

  Amines are nucleophile because they have a lone pair of electrons on the nitrogen atom. The reaction produces an N-substituted amide

  
  

  R1COCl + R2NH2 -> R1-CONHR2 + HCl
• How do acyl chlorides react with ammonia?

  Product formed is an amide

  R1COCl + NH3 -> R1CONH2 + NH4Cl
• How do acid anhydrides react with water?

  Produce two Carboxylic acids
• How do acid anhydrides react with alcohol?

  Produce a carboxylic acid and ester
• How do acid anhydrides react with primary amines?

  Produce an N-substituted amide and an alkyl ammonium carboxylate salt (R1-COO- + NH3R2+
• How do acid anhydrides react with ammonia?


  Produce an amide and an ammonium carboxylate salt