Experiment 8: Carboxylic Acids

• What are carboxylic acids classified as?

  Weak organic acids
• What is the general formula for carboxylic acids?

  1. COOH
• What is the structure of a carboxyl group?

  Carbonyl carbon double bonded to oxygen
• What charge does the oxygen from the hydroxyl group exhibit?

  Partially negative charge
• What charge does the hydrogen from the hydroxyl group exhibit?

  Partially positive charge
• What can the R group in carboxylic acids be?

  An alkyl group of any chain
• How do carboxylic acids interact with water molecules?

  They form hydrogen bonds
• What is the result of hydrogen bonding between carboxylic acids?

  Formation of dimers
• What are carboxylic acid derivatives?

  Compounds convertible to carboxylic acids
• What is an acyl group?

  A carbonyl group attached to an alkyl
• What influences the identity of a carboxylic acid derivative?

  The leaving group attached to carbonyl carbon
• What is the mechanism of reaction for carboxylic acid derivatives?

  Nucleophilic Acyl Substitution (SNacyl)
• What does the reactivity of carboxylic acid derivatives depend on?

  Relative basicity strength of the leaving group
• How does the leaving group influence reactivity?

  It stabilizes the charge of carbonyl carbon
• Which derivatives react almost instantaneously?

  Acid chloride and Acid anhydride
• Why is the carbonyl carbon in acid chloride more electrophilic?

  Due to the chloride leaving group
• How does the basicity of the amine leaving group affect amides?

  It decreases the electrophilic character
• What is the relationship between reactivity and reaction rate?

  More reactive means higher reaction rate
• What is required for nucleophilic acyl substitution to occur?

  Presence of a catalyst (acid or base)
• What are the steps in the hydrolysis procedure for carboxylic acid esters?

  1. Place 20 drops of ethyl acetate in a test tube.
  2. Add 25 drops of 25% NaOH.
  3. Test the mixture with litmus papers.
  4. Acidify with 10% HCl if basic.
• What are the steps in the hydrolysis procedure for carboxylic acid amides?

  1. Place approx 0.5g of benzamide in a test tube.
  2. Add 5 mL 10% NaOH and heat until boiling.
  3. Test gas evolved with moist red litmus paper.
• What happens during hydrolysis of carboxylic acid derivatives?

  They yield carboxylic acids
• What is the role of water in hydrolysis?

  Water acts as a nucleophile
• How does the stability of a derivative affect hydrolysis rate?

  More stable derivatives hydrolyze slower
• Which derivatives react rapidly with water?

  Acid chlorides and anhydrides
• What is required for esters to undergo hydrolysis?

  An acid or base catalyst
• What is required for amides to undergo hydrolysis?

  Prolonged heating with concentrated catalyst
• What is the mechanism of hydrolysis for all derivatives?

  Nucleophilic acyl substitution reaction
• What does the nucleophile do in hydrolysis?

  Attacks the positive carbocation
• What happens to the tetrahedral intermediate in hydrolysis?

  It reforms a double bond with carbon
• What is expelled during hydrolysis?

  The leaving group (halogen)
• What is the product of hydrolysis?

  A carboxylic acid
• How do acid chlorides and anhydrides react with water?

  Rapidly, without catalysts
• What happens when water attacks acetic anhydride?

  Forms a tetrahedral intermediate
• What is the result of tautomerization in anhydride hydrolysis?

  Formation of another complex
• What is produced from the elimination process in anhydride hydrolysis?

  Two moles of acetic acid
• What is observed when acetyl chloride is added to water?

  Warming effect occurs
• What is formed when acetyl chloride reacts with 2% AgNO3?

  White precipitate (AgCl)
• What happens when acetic anhydride is added to water?

  No warming effect observed
• What is the process of basic hydrolysis of esters called?

  Saponification