OrgChem MIDTERM

• Acid


  A substance which donates an H+ ion or a proton and forms its conjugate base
• Weak Bronsted -Lowry acids


  Those which have a little tendency to donate a proton and their corresponding conjugated base is strong
• Bronsted-Lowry theory


  Acid-base reaction involving the transfer of protons or H+ ions between the acid and base
• Conjugated acid


  Can donate a proton and base reforms
• Base


  A substance which accepts an H+ ion or a proton and forms its conjugate acid
• Strong Bronsted-Lowry acids


  Those which have a strong tendency to give a proton and their corresponding conjugate base is weak
• Conjugate base


  Can accept a proton and acid reforms
• Bronsted-Lowry theory is an acid-base reaction theory introduced by Johannes Nicolaus Bronsted (Danish Chemist) and Thomas Martin Lowry (English Chemist) in 1923
• Separating water and sand


  Use filter paper, water molecules pass through the tiny pores while sand particles do not
• Cholesterol


  • It is a steroid, a type of lipid, nonpolar, and largely water insoluble but dissolves in a nonpolar solvent like ether
• Extraction technique

  Separating sodium chloride and cholesterol by using their physical properties
• Separating a mixture of 4-chloroaniline, benzoic acid, and 1,4-dibromobenzene

  Use acid-base reactions to separate the compounds
• Benzoic acid


  • It is acidic
• Separating 4-chloroaniline, benzoic acid, and 1,4-dibromobenzene

  Use acid-base reactions with hydrochloric acid to separate the compounds based on their reactivity
• Separating sodium chloride and cholesterol

  Add water and ether, use a separatory funnel to get two layers - aqueous layer with water and sodium chloride, organic layer with ether and cholesterol
• Sodium chloride


  • It is an ionic compound that is water soluble
• 1. chloroaniline


  • It is somewhat basic and reacts with a strong acid like hydrochloric acid
• Separating a mixture with several small molecules

  Use physical properties like solubility or chemical properties like reactivity
• 1,4-dibromobenzene


  • It is neither basic nor acidic
• Separation of benzoic acid salt

  Add base (sodium bicarbonate), shake, vent, collect aqueous layer in a labeled flask, wash with base, wash with water
• Deprotonation of aniline salt

  Add strong base (sodium hydroxide), immerse in cold water bath, watch 4-chloroaniline precipitate, check pH to ensure completion, filter and dry
• Extraction is a technique ubiquitous in the organic chemistry laboratory
• Extraction process

  Shake, vent, drain aqueous layer into a new flask, wash organic layer with acid, repeat process, wash with deionized water, collect all three aqueous extracts in the same flask
• Contents of the reaction flask are transferred to a separatory funnel for extraction
• Separation of aniline salt

  Add base (sodium bicarbonate), shake, vent, collect aqueous layer in a labeled flask, wash with base, wash with water
• Evaporation of dibromobenzene

  Put on a hot plate, use a low setting to gently evaporate the ether away, residue remains as dibromobenzene
• Protonation of benzoic acid salt

  Add strong acid (HCl), watch benzoic acid precipitate, check pH to ensure completion, filter and dry
• Almost every single time a reaction is performed, it will end with some kind of aqueous workup to neutralize any ionic products
• Understanding extraction is essential for organic chemistry laboratory work
• Lewis acids and bases are named after the American chemist Gilbert Newton Lewis, who also made invaluable contributions in the fields of thermodynamics and photochemistry
• Lewis Bases


  • Most common examples: ammonia, alkyl amines, conventional amines
  • Lewis bases are electron-rich species that donate electron pairs and can be classified as nucleophiles
• Common Lewis acids

  • H+ ions (or protons), onium ions like H3O+
  • Cations of d block elements with high oxidation states e.g., Fe3+
  • Cations of metals like Mg2+ and Li+ forming aquo complexes with water
  • Carbocations like H3C+
  • Pentahalides of Antimony, Arsenic, and Phosphorus
• Examples of Lewis bases


  • Pyridine and its derivatives
  • Compounds with Oxygen, Sulphur, Selenium, and Tellurium in -2 oxidation state like water and ketones
  • Simple anions like H– and F–, complex anions like sulfate anion (SO42-)
• Lewis Bases

  Atomic or molecular species with a highly localized HOMO (The Highest Occupied Molecular Orbital)
• Lewis Acids


  Chemical species with empty orbitals able to accept electron pairs from Lewis bases
• Common Lewis bases

  • Ammonia, alkyl amines, other conventional amines
• Lewis Acids


  • Term used to describe chemical species with a trigonal planar structure and an empty p-orbital
  • Example: BR3 (where R can be a halide or an organic substituent)
• Lewis Base


  Atomic or molecular species with a highly localized HOMO (The Highest Occupied Molecular Orbital)
• Lewis Acids

  Chemical species with empty orbitals able to accept electron pairs from Lewis bases
• Lewis acids and bases are named after the American chemist Gilbert Newton Lewis, who also made invaluable contributions in the fields of thermodynamics and photochemistry