C1L2 - Introduction to Organic Chemistry

• Water has a bent tetrahedral molecular geometry shaped like the letter V.
• In water molecules, oxygen has partial negative charge and hydrogen has a partial positive charge.
• Hydrogen bonds cause the interactions of water molecules-this is the reason for their emergent properties.
• Main properties of water include

  1. Cohesion
  2. Thermoregulation
  3. Floating
  4. Universal Solvent
• Cohesion - due to hydrogen bonding, water molecules are attracted to each other.
• Surface Tension - due to cohesion, this results and the surface of the liquid becomes hard to break or stretch.
• Cohesion contributes to the transport of nutrients against gravity called capillary action.
• Adhesion - water can hydrogen bond extrinsically with other molecules. This helps to transport nutrients in the body.
• Kinetic Energy - this is the energy acquired from any movement of an object.
• More amount of substance = higher transfer of thermal energy
• Thermal Energy - sum of kinetic energies due to random atomic motions.
• Temperature - this is the average kinetic energies due to random atomic motions.
• Heat - this is the transfer of thermal energy in order to reach equilibrium.
• Heat is measured in calories, and 1 unit of which is equivalent to 4.184 Joules.
• Specific heat is defined as the energy required to raise the temperature of 1g of a substance by 1°C.
• Specific heat measures well a substance resists temperature changes when heat is applied.
• Water has high specific heat capacity

  • This property allows thermoregulation and stabilization of environmental conditions
  • This is also responsible for sea and land breeze phenomena
• Heat of Vaporization - energy required to convert 1g of a liquid into gas.
• Water has high heat of vaporization, manifested through:

  1. Climate moderation
  2. Steam burns [hurts when condenses in skin]
  3. Evaporative cooling
• Water is densest at 4 °C, less dense as a solid than a liquid.
• At 0°C, the molecules form crystalline lattice structure, each water molecule hydrogen bonded to four partners.
• Water is known as the universal solvent because of its polarity.
• Oxygens are attracted to the cation, while hydrogens are attracted to the anion. Because of this, water forms a shield around the ions called hydration shell, causing it to be dissolved.
• Acids

  • increase concentrations of H+ ions
  • they have pH of <7
  • they are positively charged
• Bases

  • decrease concentrations of H+ ions
  • they have pH of >7
  • they are negatively charged
• Weak acids - are acids that reversibly release and accept back hydrogen ions.
• Once the concentrations of OH and H are equal in a solution, they are said to be neutral.
• pH = - log [H+]
• If an acid is added and [H+] increased from 10^-14 to 10^-n, then [OH-] decreases from 10^-14 to 10^-14+n
• If 0.01 mol of a strong acid is added to a liter of pure water, the pH drops from 7.0 to 2.0.
• Buffers - a chemical that can absorb a change in pH and return it to a more stable level
• Buffer solutions contain:

  1. Weak acid
  2. Base
• In buffers, weak acids serve as H+ donor
• In buffers, bases serve as H+ acceptor
• Ocean acidification - CO2 dissolves in ocean, forming carbonic acid, making the pH more acidic.
• • Carbonate ions are used in calcification by marine organisms like corals.
  • Calcification is done by combining Calcium and Carbonate ions.
  • CO2 dissolves in the ocean, reacts with water, forming carbonic acid
  • Carbonic acid dissociates into H+ and bicarbonate ion
  • Free H+ combines with carbonate ions forming bicarbonate.
  • Less carbonate means slower rate of calcification.
• Carbon has 4 main characteristics:

  1. It is tetravalent
  2. It has many allotropes
  3. It is highly unreactive under normal conditions
  4. It has ability to bond with multiple elements like Hydrogen, Oxygen, and Nitrogen
• Stanley Miller is a grad student under Harold Urey at University of Chicago in 1953.
• Stanley miller designed an experiment to test the hypothesis that the first life on earth was formed by a chemical reaction between amino acids and simple organic compounds.
• Hydrocarbons - molecules made up of only hydrogen and carbon atoms