OrganicChemistry3e_lectureppt_Ch01

CHAPTER 1: Atomic and Molecular Structure

1.1 What is Organic Chemistry?

• Organic chemistry involves the study of organic compounds.

• Initially defined in the 1700s as collections from living organisms.

• Inorganic compounds encompass everything else that is not organic.

1.2 Why Carbon?

• Carbon can form four covalent bonds, allowing for complex structures.

• Forms chains of various lengths, including branched, straight, or ring structures.

• Capable of forming single, double, or triple bonds between atoms.

1.3 Atomic Structure and Ground State Electron Configurations

• Atoms consist of a central positively charged nucleus with protons and neutrons.

• The electron cloud determines the size of the atom, predominantly empty space.

Structure of an Atom

• Atoms have no net charge; the number of electrons equals the number of protons.

• Atomic number (Z) is determined by the number of protons.

• Ions:

  • Cation: More protons than electrons

  • Anion: More electrons than protons

  • Particles:

    • Proton: Charge +1, mass ~1 u

    • Neutron: Charge 0, mass ~1 u

    • Electron: Charge -1, mass ~0.0005 u

1.4 The Covalent Bond: Bond Energy and Bond Length

• A covalent bond forms by the sharing of valence electrons between atoms.

• Bond strength and length vary with the number of shared electrons:

  • Single bond: 2 electrons

  • Double bond: 4 electrons

  • Triple bond: 6 electrons

Energy and Stability of Covalent Bonds

• A H2 molecule is more stable than two isolated H atoms due to the stability provided by covalent bonding.

• Electrons in a covalent bond are attracted by both nuclei, making for lower energy states when bonded.

1.5 Lewis Dot Structures and the Octet Rule

• Lewis structures visually represent molecule connectivity.

• Guidelines for drawing:

  1. Count total valence electrons.

  2. Sketch the skeleton with single bonds.

  3. Subtract electrons for bonds, distribute remaining as lone pairs.

  4. Convert lone pairs to create double/triple bonds if needed.

1.6 Strategies for Success: Drawing Lewis Dot Structures Quickly

• Understanding common bonding patterns is key for efficiency.

1.7 Electronegativity, Polar Covalent Bonds, and Bond Dipoles

• Covalent bonds can be nonpolar (identical atoms) or polar (different atoms).

• Electronegativity (EN) determines the strength of electron attraction between atoms, affecting bond polarity.

1.8 Ionic Bonds

• Ionic bonds occur due to significant differences in electronegativity.

• Elements on the left side of the periodic table tend to lose electrons, while right-side elements gain them.

1.9 Assigning Electrons to Atoms: Formal Charge

• Formal charge helps determine the charge of atoms in covalent molecules based on electron sharing.

1.10 Resonance Theory

• Lewis structures sometimes inadequately describe molecules due to electron delocalization.

• Resonance structures illustrate different possible electron configurations without altering atom positions.

1.11 Strategies for Success: Drawing All Resonance Structures

• Electrons' movement in resonating structures can be depicted using curved arrows.

1.12 Shorthand Notations

• Chemists often use shorthand notations to simplify the representation of structures in complex organic chemistry.

1.13 An Overview of Organic Compounds: Functional Groups

• Functional groups dictate a molecule's reactivity and behavior.

• Alkanes are defined as compounds with only C–C and C–H single bonds.

Common Functional Groups

• Alkene: C=C

• Thiol: C–SH

• Aldehyde: –CHO

• Amine: –NH2...

1.14 Introduction to Biomolecules

• Four major classes of biomolecules in living organisms: proteins, carbohydrates, nucleic acids, lipids.

Proteins and Amino Acids

• Amino acids are the building blocks of proteins.

• Proteins perform various functions, including structural roles in tissues.

Carbohydrates

• Carbohydrates serve several biological functions and are categorized primarily as monosaccharides (simple sugars) and polysaccharides (complex carbohydrates).

Nucleic Acids and Nucleotides

• Nucleic acids store and transfer genetic information, consisting of nucleotides made up of:

  • An inorganic phosphate group

  • A cyclic sugar

  • A nitrogenous base.