Ch. 1 - A Review of General ChemistrySee all chapters
All Chapters
Ch. 1 - A Review of General Chemistry
Ch. 2 - Molecular Representations
Ch. 3 - Acids and Bases
Ch. 4 - Alkanes and Cycloalkanes
Ch. 5 - Chirality
Ch. 6 - Thermodynamics and Kinetics
Ch. 7 - Substitution Reactions
Ch. 8 - Elimination Reactions
Ch. 9 - Alkenes and Alkynes
Ch. 10 - Addition Reactions
Ch. 11 - Radical Reactions
Ch. 12 - Alcohols, Ethers, Epoxides and Thiols
Ch. 13 - Alcohols and Carbonyl Compounds
Ch. 14 - Synthetic Techniques
Ch. 15 - Analytical Techniques: IR, NMR, Mass Spect
Ch. 16 - Conjugated Systems
Ch. 17 - Aromaticity
Ch. 18 - Reactions of Aromatics: EAS and Beyond
Ch. 19 - Aldehydes and Ketones: Nucleophilic Addition
Ch. 20 - Carboxylic Acid Derivatives: NAS
Ch. 21 - Enolate Chemistry: Reactions at the Alpha-Carbon
Ch. 22 - Condensation Chemistry
Ch. 23 - Amines
Ch. 24 - Carbohydrates
Ch. 25 - Phenols
Ch. 26 - Amino Acids, Peptides, and Proteins

When atomic orbitals interfere constructively with each other, they increase the chances of finding electrons between nuclei, forming what we call a bond.

Types of Bonds
  • A sigma (σ)-bond is formed by one region of constructive overlap between orbitals (regardless of the type of orbital used).
  • A pi (π)-bond is formed by two regions of constructive overlap between orbitals (p-orbitals).

Concept #1: What’s the difference between sigma and pi bonds?

The LCAO Model: Predicting Molecular Orbitals

Concept #2: What’s the difference between atomic and molecular orbitals? 

The hexagon-thingy in the middle is the LCAO (Linear Combination of Atomic Orbitals):

  • The side orbitals are your atomic orbitals (like you are used to drawing)
  • The top and bottom orbitals represent atomic orbital overlap (molecular orbitals).
  •  When atomic orbitals constructively interfere, they create bonding molecular orbitals that are more stable than the original atomic orbitals.
Bond Lengths and Strengths

Concept #3: Sigma bond vs. pi bond, which is stronger? 

Hey! Turn that frown upside-down. I know this section blows. The rest of this chapter should be cake compared to this.