Lecture Notes on Chemical Bonds and Water Molecules

Overview of Cellulose Chains

• Cellulose Chains:
  • Form hydrogen bonds with each other.
  • Oxygen carries a partially negative charge; hydrogen carries a partially positive charge.

Water Molecules

• Structure of Water (H₂O):

  • Composed of two hydrogen atoms covalently bonded to one oxygen atom.
  • Hydrogen atoms share electrons with oxygen, making the oxygen's valence shell complete with 8 electrons.
  • Covalent bond: Electron sharing between hydrogen and oxygen.

• Electron Distribution in Water:

  • Oxygen end has a surplus of electrons, creating a partially negative charge (Δ-).
  • Hydrogen ends have fewer electrons, leading to a partially positive charge (Δ+).
  • Unequal electron distribution leads to dipole characteristics.

Dipole Nature of Water

• Dipole Explanation:

  • Water is a dipole due to its two charges: partially positive (hydrogen) and partially negative (oxygen).
  • Dipole: Two opposite charges within the same molecule.

• Hydrogen Bonding in Water:

  • Partial charges lead to hydrogen bond formation.
  • Hydrogen bonds are indicated by dotted lines.
  • Oxygen's size allows it to form two hydrogen bonds simultaneously.
  • Hydrogen can only form one hydrogen bond due to size constraints.

Other Molecules Forming Hydrogen Bonds

• Hydrogen Bond Formation Capabilities:

  • Molecules with OH, NH, and CO groups can form hydrogen bonds.
  • OH Group: Hydrogen is partially positive.
  • NH Group: Hydrogen is partially positive.
  • C=O Group: Oxygen is partially negative.
  • Important for understanding amino acids and lipids.

• Example of Hydrogen Bond Formation:

  • Molecule with OH group forming hydrogen bond with molecule having CO group due to opposite partial charges.

Key Takeaways

• Understanding electron distribution and partial charges helps explain hydrogen bonding.
• Size of atoms (oxygen vs. hydrogen) impacts their ability to form multiple hydrogen bonds.
• Reading molecular interactions is crucial for studying biological molecules like amino acids and lipids.