Exer 4 chem 31.1

• Esters


  Among the most common of all naturally occurring compounds, usually responsible for the pleasant smell of fruits and flowers, used industrially as solvents and plasticizers
• Esterification


  1. Carboxylic acid or its derivatives and an alcohol react

  2. Acid is usually used to hasten the reaction
• Salicylic acid


  Di-functional organic compound with a carboxyl and hydroxyl group both attached to a benzene ring, can undergo two different esterification reactions
• Acetylsalicylic acid (aspirin)


  Most widely used medicine in the world, has the ability to reduce fever, pain and to act as an anti-inflammatory agent
• Preparation of aspirin


  Salicylic acid acts as an alcohol and reacts with acetic anhydride in the presence of sulfuric acid as a catalyst
• Methyl salicylate (oil of wintergreen)


  Prepared from the reaction of salicylic acid and methanol, used in perfumes and as a flavoring agent, undergoes hydrolysis with water to form salicylic acid
• Recrystallization


  Impure solid compound is dissolved in a warm solvent, the warm solution is filtered and then crystals are allowed to reform as the solution cools
• Ideal solvent for recrystallization

  • Readily dissolves the solute at elevated temperatures and sparingly at lower temperatures
  • Dissolves the desired solute and not the impurities
  • Chemically inert to the solute
  • Allows the solute to give well-formed crystals upon cooling
  • Highly volatile to permit easy removal from the purified crystals
• Inducing crystal formation


  1. Seeding - addition of a pure solid compound with the same composition

  2. Scratching the walls of the container
• Old bottle of aspirin, when opened, smells like vinegar
• FeCl3 will not result in a color change when added to oil of wintergreen
• Synthesis of aspirin


  Salicylic acid acts as an alcohol and reacts with acetic anhydride in the presence of sulfuric acid as a catalyst
• Synthesis of oil of wintergreen

  Salicylic acid reacts with methanol in the presence of concentrated sulfuric acid
• Purpose of FeCl3 in characterization of aspirin

  To test for the presence of phenolic group
• Recrystallized aspirin may not be pure, possible sources of errors include choice of solvent and incomplete recrystallization
• Characterization tests help explain the properties of the synthesized compounds